Mapping YANG to Document Schema
Definition Languages and Validating NETCONF ContentCESNETlhotka@cesnet.czPlantronicsrohan@ekabal.comNortelschishol@nortel.com
Operations and Management
NETMODThis draft describes the mapping rules for translating YANG
data models into XML schemas using Document Schema Definition
Languages (DSDL) and outlines the procedure for validating various
types of NETCONF protocol data units using these schemas.The NETCONF Working Group has completed a base protocol used
for configuration management . This base
specification defines protocol bindings and an XML container
syntax for configuration and management operations, but does not
include a modeling language or accompanying rules for how to model
configuration and status information (in XML syntax) carried by
NETCONF. The IETF Operations Area has a long tradition of defining
data for SNMP Management Information Bases (MIBs) using the SMI language
to model its data. While this specific modeling approach has a
number of well-understood problems, most of the data modeling
features provided by SMI are still considered extremely important.
Simply modeling the valid syntax rather than additional semantic
relationships has caused significant interoperability problems in
the past.The NETCONF community concluded that a data modeling framework
is needed to support ongoing development of IETF and
vendor-defined management information modules. The NETMOD Working
Group was chartered to address this problem, by defining a new
human-friendly modeling language based on SMIng and called YANG . Since NETCONF uses XML for encoding its protocol data units
(PDU), it is natural to express the constraints on NETCONF content
using standard XML schema languages. For this purpose, the NETMOD
WG selected the Document Schema Definition Languages (DSDL) that
is being standardized as ISO/IEC 19757 . The
DSDL framework comprises a set of XML schema languages that
address grammar rules, semantic constraints and other data
modeling aspects but also, and more importantly, do it in a
coordinated and consistent way. While it is true that some DSDL
parts have not been standardized yet and are still work in
progress, the three parts that the YANG-to-DSDL mapping relies
upon - RELAX NG, Schematron and DSRL - already have the status of
an ISO/IEC International Standard and are supported in a number of
software tools.This document contains the specification of a mapping that
translates YANG data models to XML schemas utilizing a subset of
the DSDL schema languages. The mapping procedure is divided into
two steps: In the first step, the structure of the data tree, RPC
signatures and notifications is expressed as a single RELAX NG
grammar with simple annotations representing additional data model
information (metadata, documentation, semantic constraints,
default values etc.). The second step then generates a coordinated
set of DSDL schemas that can validate specific XML documents such
as client requests, server responses or notifications, perhaps
also taking into account additional context such as active
capabilities.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in .In the text, we also use the following typographic conventions:
YANG statement keywords are delimited by single quotes.Literal values are delimited by double quotes.XML element names are delimited by "<" and ">" characters.Names of XML attributes are prefixed by the "@" character.XML elements names are always written with explicit namespace
prefixes corresponding to the following XML vocabularies:
DTD compatibility annotations Dublin Core metadata elements NETCONF protocol NETCONF event notifications NETMOD-specific schema annotations
(see )Conceptual tree (see )Document Semantics Renaming
Language RELAX NG ISO Schematron W3C XML Schema
The following table shows the mapping of these prefixes to
namespace URIs.PrefixNamespace URIahttp://relaxng.org/ns/compatibility/annotations/1.0dchttp://purl.org/dc/termsncurn:ietf:params:xml:ns:netconf:base:1.0enurn:ietf:params:xml:ns:netconf:notification:1.0nmaurn:ietf:params:xml:ns:netmod:dsdl-annotations:1nmturn:ietf:params:xml:ns:netmod:conceptual-tree:1dsrlhttp://purl.oclc.org/dsdl/dsrlrnghttp://relaxng.org/ns/structure/1.0schhttp://purl.oclc.org/dsdl/schematronxsdhttp://www.w3.org/2001/XMLSchemaThe main objective of this work is to complement YANG as a data
modeling language by validation capabilities of DSDL schema
languages, primarily RELAX NG and Schematron. This document
describes the correspondence between grammatical, semantic and data
type constraints expressed in YANG and equivalent DSDL
constructs. The ultimate goal is to be able to capture all
substantial information contained in YANG modules and express it
in DSDL schemas. While the mapping from YANG to DSDL described in
this document is in principle invertible, the inverse mapping from
DSDL to YANG is not in its scope.XML-encoded data appear in several different forms in various
phases of the NETCONF workflow - configuration datastore contents,
RPC requests and replies, and notifications. Moreover, RPC methods
are characterized by an inherent diversity resulting from
selective availability of capabilities and features. YANG modules
can also define new RPC methods. The mapping should be able to
accommodate this variability and generate schemas that are
specifically tailored to a particular situation and thus
considerably more efficient than generic all-encompassing
schemas.In order to cope with this variability, we assume that the
schemas can be generated on demand from the available collection
of YANG modules and their lifetime will be relatively short. In
other words, we don't envision that any collection of DSDL schemas
will be created and maintained over extended periods of time in
parallel to YANG modules.The generated schemas are primarily intended as input to the
existing XML schema validators and other off-the-shelf
tools. However, the schemas may also be perused by developers and
users as a formal representation of constraints on a particular
XML-encoded data object. Consequently, our secondary goal is to
keep the schemas as readable as possible. To this end, the complexity
of the mapping is distributed into two steps:
The first step maps one or more YANG modules
to a single RELAX NG schema of the so-called "conceptual tree",
which contains grammatical constraints for the main data tree as
well as RPCs and notifications. In order to record additional
constraints that appear in the YANG modules but cannot be
expressed in RELAX NG, the schema is augmented by simple
annotations. The resulting schema should thus be considered a
reasonably readable equivalent of the input YANG modules.In the second step, the annotated RELAX NG schema from step
is transformed further
to a coordinated set of DSDL schemas containing constraints for
a particular data object and a specific situation. The DSDL
schemas are intended mainly for machine validation using
off-the-shelf tools.The mapping described in this document uses three of the DSDL
schema languages, namely RELAX NG, Schematron and DSRL.RELAX NG (pronounced "relaxing") is an XML schema language
for grammar-based validation and Part 2 of the ISO/IEC DSDL
family of standards . Like the W3C XML
Schema language , it is able to describe
constraints on the structure and contents of XML
documents. However, unlike the DTD and XSD
schema languages, RELAX NG intentionally avoids any infoset
augmentation such as defining default values. In the DSDL
architecture, the particular task of defining and applying
default values is delegated to another schema language, DSRL
(see ).As its base datatype library, RELAX NG uses the W3C XML
Schema Datatype Library , but unlike XSD,
other datatype libraries may be used along with it or even
replace it if necessary. RELAX NG is very liberal in accepting annotations from other
namespaces. With few exceptions, such annotations may be placed
anywhere in the schema and need no encapsulating element such
as <xsd:annotation> in XSD.RELAX NG schema can be represented using two equivalent
syntaxes: XML and compact. The compact syntax is described in
Annex C of the RELAX NG specification ,
which was added to the standard in 2006 (Amendment 1). Automatic
bidirectional conversions between the two syntaxes can be
accomplished using for example Trang.
For its terseness and readability, the compact syntax is
often the preferred form for publishing RELAX NG schemas whereas
validators and other software tools generally require the XML
syntax. However, the compact syntax has two drawbacks:
External annotations make the compact syntax schema
considerably less readable. While in the XML syntax the
annotating elements and attributes are represented in a simple
and uniform way (XML elements and attributes from foreign
namespaces), the compact syntax uses four different syntactic
constructs: documentation, grammar, initial and following
annotations. Therefore, the impact on readability that results
from adding annotations is often much stronger for the compact
syntax than for the XML syntax.In a program, it is more difficult to generate compact
syntax than XML syntax. While a number of software libraries
exist that make it easy to create an XML tree in memory and
serialize it, no such aid is available for compact syntax.
For these reasons, the mapping specification in this document
use exclusively the XML syntax. Where appropriate, though, the
schemas resulting from the translation may be presented in the
equivalent compact syntax.RELAX NG elements are qualified with the namespace URI
"http://relaxng.org/ns/structure/1.0". The namespace of the W3C
Schema Datatype Library is
"http://www.w3.org/2001/XMLSchema-datatypes".Schematron is Part 3 of DSDL that reached the status of a
full ISO/IEC standard in 2006 . In
contrast to the traditional schema languages such as DTD, XSD or
RELAX NG, which are based on the concept of a formal grammar,
Schematron utilizes a rule-based approach. Its rules may
specify arbitrary conditions involving data from different parts
of an XML document. Each rule consists of three essential parts:
Context - an XPath expression that defines the set of
locations where the rule is to be applied,Assert or report condition - another XPath expression that
is evaluated relative to the location matched by the context
expression.Human-readable message that is displayed when the assert
condition is false or report condition is true.
The difference between the assert and report condition is that
the former is positive in that it states a condition that a
valid document has to satisfy, whereas the latter specifies an
error condition.Schematron draws most of its expressive power from XPath
and XSLT . ISO
Schematron allows for dynamic query language binding so that the
following XML query languages can be used: STX, XSLT 1.0, XSLT
1.1, EXSLT, XSLT 2.0, XPath 1.0, XPath 2.0 and XQuery 1.0 (this
list may be extended in future).The human-readable error messages are another feature that
distinguishes Schematron from other schema languages such as
RELAX NG or XSD. The messages may even contain XPath expressions
that are evaluated in the actual context and thus refer to
existing XML document nodes and their content.ISO Schematron introduced the concept of abstract patterns whose purpose is similar
to functions in programming languages. The mapping described in
this document uses a library of abstract patterns for specifying
generic constraints such as uniqueness of certain leaf values in
list items.The rules defined by a Schematron schema may be divided into
several subsets known as phases. Validations may then be set up to
include only selected phases. In the context of NETCONF data
validation, this is useful for relaxing constraints that may not
always apply. For example, the reference integrity may not be
enforced for a candidate configuration.Schematron elements are qualified with namespace URI
"http://purl.oclc.org/dsdl/schematron".DSRL (pronounced "disrule") is Part 8 of DSDL that reached
the status of a full ISO/IEC standard in 2008 . Unlike RELAX NG and Schematron, it is
specifically designed to modify XML information set of the
validated document. The primary application for DSRL is renaming
XML elements and attributes. DSRL can also define default values
for XML attributes and elements so that elements or attributes
with these default values are inserted if they are missing in
the validated documents. The latter feature is used by the
YANG-to-DSDL mapping for representing YANG defaults for leaf
nodes.DSRL elements are qualified with namespace URI
"http://purl.oclc.org/dsdl/dsrl".In addition to the DSDL schema languages, the mapping uses
three sets of annotations that are added as foreign-namespace
elements and attributes to RELAX NG schemas. Two of the annotation
sets - Dublin Core elements and DTD compatibility annotations -
are standard vocabularies for representing metadata and
documentation, respectively. While these data model items may not
be used for formal validation, they quite often carry important
information. Therefore, they SHOULD be included in the conceptual tree
schema and MAY also appear in the final validation schemas.The third set are NETMOD-specific annotations conveying
semantic constraints and other information that cannot be
expressed natively in RELAX NG. These annotations are only used in
the first step of the mapping, i.e., in the conceptual tree
schema. In the second mapping step, these annotations are
converted to Schematron and DSRL rules.Dublin Core is a
system of metadata elements that was originally created for
describing metadata of World Wide Web resources in order to
facilitate their automated lookup. Later it was accepted as a
standard for describing metadata of arbitrary resources. This
specification uses the definition found in . Dublin Core elements are qualified with namespace URI
"http://purl.org/dc/terms".DTD compatibility annotations are part of the RELAX NG DTD
Compatibility specification . The
YANG-to-DSDL mapping uses only the <a:documentation>
annotation for representing YANG 'description' and 'reference'
texts.Note that there is no intention to make the resulting schemas
DTD-compatible, the main reason for using these annotations is
technical: they are well supported and adequately interpreted by
several RELAX NG tools.DTD compatibility annotations are qualified with namespace
URI "http://relaxng.org/ns/compatibility/annotations/1.0".NETMOD-specific annotations are XML elements and attributes
qualified with the namespace URI
"urn:ietf:params:xml:ns:netmod:dsdl-annotations:1" that appear
in various locations in the conceptual tree schema. YANG
statements are mapped to these annotations in a very
straightforward way. With one exception - @nma:default-case -
the annotation attributes and elements always have the same name
as the corresponding YANG statement. lists alphabetically the names of
NETMOD-specific annotation elements (in angle brackets) and
attributes (prefixed with "@") along with a reference to the
section where their use is described. then contains the RELAX NG schema of this
annotation vocabulary.annotationsectionnote@nma:config@nma:default@nma:default-case<nma:error-app-tag><nma:error-message><nma:instance-identifier>@nma:key<nma:leafref>@nma:min-elements@nma:max-elements<nma:must>@nma:ordered-by@nma:presence@nma:status@nma:unique@nma:units@nma:whenNotes:
Appears only as subelement of
<nma:must>.Has an optional attribute
@require-instance.Has a mandatory attribute @assert and
two optional subelements <nma:error-app-tag> and
<nma:error-message>.This section gives an overview of the YANG-to-DSDL mapping, its
inputs and outputs. presents an overall
structure of the mapping:
+----------------+
| YANG module(s) |
+----------------+
|
|T
|
+-------------------------------------+
| RELAX NG schema for conceptual tree |
+-------------------------------------+
/ | | \
/ | | \ +-------+
Tg/ Tr| |Tn \ |library|
/ | | \ +-------+
+---------+ +-----+ +-------+ +------+
|get reply| | rpc | | notif | | .... |
+---------+ +-----+ +-------+ +------+
The mapping procedure is divided into two steps:
Transformation T in the first step maps one or more YANG
modules to a single RELAX NG schema for the conceptual tree (see
). Constraints that cannot be
expressed directly in RELAX NG (list key definitions, 'must'
statements etc.) and various documentation texts are recorded in
the schema as simple annotations belonging to special
namespaces.In the second step, the conceptual tree schema is transformed
in multiple ways to a coordinated set of DSDL schemas that can
be used for validating a particular data object in a specific
context. shows just three
simplest possibilities as examples. In the process, appropriate
parts of the conceptual tree schema are extracted and specific
annotations transformed to equivalent, but usually more complex,
Schematron patterns, <dsrl:default-content> elements
etc.As indicated in , the second
step of the mapping also uses a schema-independent library that
contains common schema objects such as RELAX NG named pattern
definitions.An implementation of the mapping algorithm accepts one or more
valid YANG modules as its input. It is important to be able to
process multiple YANG modules together since multiple modules may
be negotiated for a NETCONF session and the contents of the
configuration datastore is then obtained as the union of data
trees specified by the individual modules, which may also lead to
multiple roots. In addition, the input modules may be further
coupled by the 'augment' statement in which one module augments
the data tree of another module.It is also assumed that the algorithm has access, perhaps on
demand, to all YANG modules that the module(s) imports
(transitively).The output of the first mapping step is an annotated RELAX NG
schema for the conceptual tree, which represents a virtual XML
document containing, in its different subtrees, the entire
datastore, all RPC requests and replies, and notifications defined
by the input YANG modules. By "virtual" we mean that such an XML
document need not correspond to the actual layout of the
configuration database in a NETCONF agent, and will certainly
never appear on the wire as the content of a NETCONF PDU. Hence,
the RELAX NG schema for the conceptual tree is not intended for
any direct validations but rather as a representation of a
particular data model expressed in RELAX NG and the common
starting point for subsequent transformations that will typically
produce validation schemas. The conceptual tree is further
described in .Other information contained in input YANG modules, such as
semantic constraints or default values, are recorded as
annotations - XML elements or attributes qualified with namespace
URI "urn:ietf:params:xml:ns:netmod:dsdl-annotations:1". Metadata
describing the YANG modules are mapped to annotations utilizing
Dublin Core elements (). Finally,
documentation strings are mapped to the <a:documentation>
elements belonging to the DTD compatibility vocabulary ().The output from the second step is is a coordinated set of
three DSDL schemas corresponding to a specific data object and
context:
RELAX NG schema describing the grammatical and datatype
constraints;Schematron schema expressing other constraints such as
uniqueness of list keys or user-specified semantic rules;DSRL schema containing a specification of default values.This section describes how the schemas generated by the
YANG-to-DSDL mapping are supposed to be applied for validating XML
instance documents corresponding to various NETCONF PDUs.The validation proceeds in the following steps, which are also
illustrated in :
The XML instance document can be immediately
checked for grammatical and data type validity using the RELAX
NG schema.Second, the default values for leaves have
to be applied and their ancestor containers added where
necessary. It is important to apply the defaults before the next
validation step because YANG specification
states that the data tree against which XPath expressions are
evaluated already has all defaults filled-in. Note that this
step modifies the information set of the input XML document.The semantic constraints are checked using
the Schematron schema.
+----------+ +----------+
| | | XML |
| XML | | document |
| document |-----------o----------->| with |
| | ^ | defaults |
| | | | |
+----------+ | +----------+
^ | filling-in ^
| grammar, | defaults | semantic
| datatypes | | constraints
| | |
+----------+ +--------+ +------------+
| RELAX NG | | DSRL | | Schematron |
| schema | | schema | | schema |
+----------+ +--------+ +------------+
The process of substituting default values is complicated by
the rules for non-presence containers and choices in YANG, which
may lead to insertion of entire subtrees in the NETCONF instance
document. describes how this
procedure is represented in DSRL and how the DSRL schema is
obtained from the conceptual tree schema.YANG modules could be mapped to DSDL schemas in a number of
ways. The mapping procedure described in this document uses
several specific design decisions that are discussed in the
following subsections.DSDL schemas generated from YANG modules using the procedure
described in this document are intended to be used for
validating XML-encoded NETCONF data in various forms (full
datastore and several types of PDUs): every YANG-based model
represents the contents of a full datastore but also implies an
array of schemas for all types of NETCONF PDUs. For a reasonably
strict validation of a given data object, the schemas have to be
quite specific. To begin with, effective validation of NETCONF
PDU content requires separation of client and server
schemas. While the decision about proper structuring of all
PDU-validating schemas is beyond the scope of this document, the
mapping procedure is designed to accommodate any foreseeable
validation needs.An essential part of the YANG-to-DSDL mapping procedure is
nonetheless common to all validation approaches: the grammar and
datatype specifications for the datastore, RPCs and
notifications expressed by one or more YANG modules have to be
translated to RELAX NG. In order to be able to separate this
common step, we introduce the notion of conceptual data tree: it is a virtual XML
tree that contains full datastore, RPC requests with
corresponding replies and notifications. The schema for the
conceptual tree - a single RELAX NG schema with annotations -
therefore has a quite similar logic as the input YANG module(s),
the only major difference being the RELAX NG schema
language.The conceptual data tree for a YANG module defining nodes in
the namespace "http://example.com/ns/example" may be
schematically represented as follows:
... configuration and status data ...
...
...
...
...
...
]]>The namespace URI
"urn:ietf:params:xml:ns:netmod:conceptual-tree:1" identifies a
simple vocabulary consisting of a few elements that encapsulate
and separate the various parts of the conceptual data tree.The conceptual tree schema is not intended for direct
validation but rather serves as a well-defined starting point
for subsequent transformations that generate various validation
schemas. Such transformations should be relatively simple, they
will typically extract one or several subtrees from the
conceptual tree schema, modify them as necessary and add
encapsulating elements such as those from the NETCONF RPC
layer.Additional information contained in the source YANG
module(s), such as semantic constraints and default values, is
represented in the form of interim NETMOD-specific annotations
that are included as foreign-namespace elements or attributes in
the RELAX NG schema for the conceptual tree. In the second phase
of the mapping, these annotations are translated to equivalent
Schematron and DSRL rules.As a useful side effect, by introducing the conceptual data
tree we are also able to resolve the difficulties arising from
the fact that a single configuration repository may consist of
multiple parallel data hierarchies defined in one or more YANG
modules, which cannot be mapped to a valid XML document. In the
conceptual data tree, such multiple hierarchies appear under the
single <nmt:top> element.Both YANG and RELAX NG offer means for modularity, i.e., for
splitting the contents into separate modules (schemas) and
combining or reusing them in various ways. However, the
approaches taken by YANG and RELAX NG differ. Modularity in
RELAX NG is suitable for ad hoc combinations of a small number
of schemas whereas YANG assumes a large set of modules similar
to SNMP MIBs. The following differences are important:
In YANG, whenever module A imports module B, it gets access
to the definitions (groupings and typedefs) appearing at the
top level of module B. However, no part of module B's data
tree is imported along with it. In contrast, the
<rng:include> pattern in RELAX NG imports both
definitions of named patterns and the entire schema tree from
the included schema.The names of imported YANG groupings and typedefs are
qualified with the namespace of the imported module. On the
other hand, the data nodes contained inside the imported
groupings, when used within the importing module, become part
of the importing namespace. In RELAX NG, the names of patterns
are unqualified and so named patterns defined in both the
importing and imported module share the same flat
namespace. The contents of RELAX NG named patterns may either
keep the namespace of the schema where they are defined or
inherit the namespace of the importing module, analogically to
YANG. However, in order to achieve the latter behavior, the
imported module must be prepared in a special way as a library
module that cannot be used as a stand-alone schema.So the conclusion is that the modularity mechanisms of YANG
and RELAX NG, albeit similar, are not directly
compatible. Therefore, the corresponding design decision for the
mapping algorithm is to collect all information in a single
schema for the conceptual tree, even if it comes from multiple
YANG modules or submodules. In other words, translations of
imported groupings and typedefs are installed in the translation
of importing module - but only if they are really used
there.NOTE: The 'include' statement that is used in YANG for
including submodules has in fact the same semantics as the
<rng:include> pattern. However, since we don't map the
modular structure for YANG modules, it seems to have little
sense to do it for submodules. Consequently, the contents of
submodules appear directly in the conceptual tree schema,
too.RELAX NG supports different styles of schema structuring:
One extreme, often called "Russian Doll", specifies the
structure of an XML instance document in a single hierarchy. The
other extreme, the flat style, uses a similar approach as the
Data Type Definition (DTD) schema language - every XML element
is introduced inside a new named pattern. In practice, some
compromise between the two extremes is usually chosen.YANG supports both styles in principle, too, but in most
cases the modules are organized in a way that's closer to the
"Russian Doll" style, which provides a better insight into the
structure of the configuration data. Groupings are usually
defined only for contents that are prepared for reuse in
multiple places via the 'uses' statement. In contrast, RELAX NG
schemas tend to be much flatter, because finer granularity is
also needed in RELAX NG for extensibility of the schemas - it is
only possible to replace or modify schema fragments that are
factored out as named patterns. For YANG this is not an issue
since its 'augment' and 'refine' statements can delve, by using
path expressions, into arbitrary depths of existing
structures.In general, it not feasible to map YANG extension mechanisms
to those of RELAX NG. For this reason, the mapping essentially
keeps the granularity of the original YANG data model:
definitions of named patterns in the resulting RELAX NG schema
usually have direct counterparts in YANG groupings and
definitions of derived types.Most modern XML schema languages including RELAX NG,
Schematron and DSRL support schemas for so-called compound XML
documents, which contain elements from multiple namespaces. This
is useful for our purpose since the YANG-to-DSDL mapping
algorithm allows for multiple input YANG modules that naturally
leads to compound document schemas.RELAX NG offers two alternatives for defining the "target"
namespaces in the schema:
First possibility is the traditional XML
way via the @xmlns:xxx attribute.One of the target namespace
URIs may be declared using the @ns attribute.In both cases these attributes are typically attached to the
<rng:grammar> element.The design decision for the mapping is to use exclusively the
alternative , since
all YANG modules are represented symmetrically, which makes
further processing of the conceptual tree schema considerably
easier. Moreover, this way the namespace prefixes declared in
all input modules are recorded in the resulting schema - the
prefix for the namespace declared using @ns would be lost.Analogically, DSRL schemas may declare the default target
namespace using the @targetNamespace attribute and any number of
additional target namespaces via the standard XML attributes
xmlns:xxx.In contrast, Schematron requires all the target namespaces to
be defined in the <sch:ns> subelements of the root
<sch:schema> element.This section explains the main principles underlying the first
step of the mapping. Its result is an annotated RELAX NG schema of
the conceptual tree, which is described in .As a special case, if the input YANG modules contain no data
nodes (this is typical e.g., for datatype library modules), an
implementation MAY entirely remove the schema of the (empty)
conceptual tree - the <rng:start> element with all its
contents. The output RELAX NG schema will then contain only named
pattern definitions translated from YANG groupings and
typedefs.Detailed specification of the mapping of individual YANG
statements is contained in .In YANG, the decision whether a given data node is mandatory
or optional is driven by the following rules, see Section
3.1 in :Leaf and choice nodes are mandatory if they contain
the substatement
mandatory true;For a choice node this means that at least one node from
exactly one case branch must exist.In addition, leaf nodes are mandatory if they are declared as
list keys.Lists or leaf-lists are mandatory if they contain
'min-elements' substatement with argument value greater than zero.A slightly more complicated situation arises for YANG
containers. First, containers with the 'presence' substatement
are always optional since their presence or absence carries
specific information. On the other hand, non-presence containers
may be omitted if they are empty. This leads to the following
recursive rule:A container node is optional if its definition contains the
'presence' substatement or none of its child nodes is
mandatory.In RELAX NG, all elements that are optional must be
explicitly wrapped in the <rng:optional> element. The mapping
algorithm thus uses the above rules to determine whether a YANG
node is optional and if so, insert the <rng:optional> element
in the RELAX NG schema.YANG groupings and typedefs are generally mapped to RELAX NG
named patterns. There are, however, several caveats that the
mapping has to take into account.First of all, YANG typedefs and groupings may appear at all
levels of the module hierarchy and are subject to lexical
scoping, see
Section 5.5 in . Moreover, top-level
symbols from external modules are imported as qualified names
represented using the external module namespace prefix and the
name of the symbol. In contrast, named patterns in RELAX NG
(both local and imported via the <rng:include> pattern)
share the same namespace and within a grammar they are always
global - their definitions may only appear at the top level as
children of the <rng:grammar> element. Consequently,
whenever YANG groupings and typedefs are mapped to RELAX NG
named pattern definitions, their names MUST be disambiguated in
order to avoid naming conflicts. The mapping uses the following
procedure for mangling the names of groupings and type
definitions:
Names of groupings and typedefs appearing at the top level of the YANG module hierarchy
are prefixed with the module name and two underscore
characters ("__").Names of other groupings and typedefs, i.e., those that do
not appear at the top level of a YANG module, are prefixed
with the module name, double underscore, and then the names of
all ancestor data nodes separated by double underscore.Since the names of groupings and typedefs in YANG have
different namespaces, an additional underline character is
added to the front of the mangled names of all groupings.For example, consider the following YANG module which imports
the standard module "inet-types" :The resulting RELAX NG schema will then contain the following
named pattern definitions (long regular expression patterns for
IPv4 and IPv6 addresses are not shown):[aeiouy]*
... regex pattern ...
... regex pattern ...
]]>YANG groupings represent a similar concept as named pattern
definitions in RELAX NG and both languages also offer
mechanisms for their subsequent modification. However, in
RELAX NG the definitions themselves are modified whereas YANG
allows for modifying expansions of
groupings. Specifically, YANG provides two statements for this
purpose that may appear as substatements of 'uses':
'refine' statement allows for changing parameters of a
schema node inside the grouping referenced by the parent
'uses' statement;'augment' statement can be used for adding new schema
nodes to the grouping content.Both 'refine' and 'augment' statements are quite powerful
in that they can address, using a subset of XPath 1.0
expressions as arguments, schema nodes that are arbitrarily
deep inside the grouping content. In contrast, definitions of
named patterns in RELAX NG operate exclusively at the topmost
level of the named pattern content. In order to achieve a
modifiability of named patterns comparable to YANG, the RELAX
NG schema would have to be extremely flat (cf. ) and very difficult to read.Since the goal of the mapping described in this document is
to generate ad hoc DSDL schemas, we decided to avoid these
complications and instead expand the grouping and refine
and/or augment it "in place". In other words, every 'uses'
statement which has 'refine' and/or 'augment' substatements is
virtually replaced by the content of the corresponding
grouping, the changes specified in the 'refine' and 'augment'
statements are applied and the resulting YANG schema fragment
is mapped as if the 'uses'/'grouping' indirection wasn't
there.If there are further 'uses' statements inside the grouping
content, they may require expansion, too: it is necessary if
the contained 'uses'/'grouping' pair lies on the "modification
path" specified in the argument of a 'refine' or 'augment'
statement.EXAMPLE. Consider the following YANG module:The resulting conceptual tree schema contains three named
pattern definitions corresponding to the three groupings,
namely
]]>and the configuration data part of the conceptual tree schema
is a single named pattern reference:
]]>Now assume that the "uses leaves" statement is refined:The resulting conceptual tree schema now contains just one
named pattern definition - "_example__fr". The other two
groupings "leaves" and "es" have to be expanded because they
both lie on the "modification path", i.e., contain the leaf
"hoja" that is being refined. The configuration data part of the
conceptual tree now looks like this:]]>RELAX NG has no equivalent of the type derivation mechanism
in YANG, where a base built-in type may be modified (in
multiple steps) by adding new restrictions. Therefore, when
mapping YANG derived types with restrictions, the derived
types MUST be "unwound" all the way back to the base built-in
type. At the same time, all restrictions found along the type
derivation chain MUST be combined and their intersection used
as facets restricting the corresponding type in RELAX NG.When a derived YANG type is used without restrictions, the
'type' statement is mapped simply to the <rng:ref>
element, i.e., a named pattern reference. However, if
restrictions are specified as substatements of the 'type'
statement, the type MUST be expanded at that point so that
only the base built-in type appears in the output schema,
restricted with facets that again correspond to the
combination of all restrictions found along the type
derivation chain and also in the 'type' statement.EXAMPLE. Consider this YANG module:The 'type' statement in "leaf month" is mapped simply to
the reference <rng:ref name="example__dozen"/> and the
corresponding named pattern is defined as follows:1
12
]]>Assume now that the definition of leaf "month" is changed
toThe output RELAX NG schema then won't contain any named
pattern definition and leaf "month" will be mapped directly
to7
12
]]>YANG uses full XPath 1.0 syntax for
the arguments of 'must' and 'when' statements and a subset
thereof in several other statements. However, since the name of
a data node always belongs to the namespace of the YANG Module
where the data node is defined, YANG adopted a simplification
similar to the concept of default
namespace in XPath 2.0: node names needn't carry a
namespace prefix inside the module where they are defined, in
which case the module's namespace is assumed.If an XPath expression is carried over to a NETMOD-specific
annotation in the first mapping step, it MUST be translated into
a fully conformant XPath 1.0 expression that also reflects the
hierarchy of the conceptual data tree:
Each unprefixed node name MUST be
prepended with the local module's namespace prefix declared by
the 'prefix' statement.Absolute XPath expressions, i.e., those
starting with a slash, MUST be prepended with appropriate path
in the conceptual tree, according to the YANG specification of
context for XPath expressions, see ,
sections 7.5.3
and 7.19.5.Translation rule
means for example that absolute XPath expressions appearing in
the main configuration data tree always start with
"nmt:netmod-tree/nmt:top/", those appearing in a notification
always start with
"nmt:netmod-tree/nmt:notifications/nmt:notification/", etc.EXAMPLE. YANG XPath expression "/dhcp/max-lease-time"
appearing in the main configuration data will be translated to
"nmt:netmod-tree/nmt:top/dhcp:dhcp/dhcp:max-lease-time".[Editor's note: We may want to introduce "$root" variable
that always contains the appropriate partial path in conceptual
tree. The translated XPath in the example would then become
"$root/dhcp:dhcp/dhcp:max-lease-time".]The key identifiers and "descendant schema node identifiers"
(see the ABNF production for "descendant-schema-nodeid" in Section 12
of ) that appear as items in the arguments
of 'key' and 'unique' statements, respectively, are special
XPath expressions and MUST be translated in the same way, i.e.,
after the translation each key and every component of a node
identifier must have the namespace prefix of the local
module.YANG allows for extending its own language in-line by adding
new statements with keywords from special namespaces. Such
extensions first have to be declared using the 'extension'
statement and then can be used as the native statements, only with
a namespace prefix qualifying the extension keyword. RELAX NG has
a similar extension mechanism - XML elements and attributes with
names from foreign namespaces may be inserted at almost every
place of a RELAX NG schema.YANG language extensions may or may not have a meaning in the
context of DSDL schemas. Therefore, an implementation MAY ignore
any or all of the extensions. However, an extension that is not
ignored MUST be mapped to XML element(s) and/or attribute(s) that
exactly match the YIN form of the extension.EXAMPLE. Consider the following extension defined by the "acme"
module:This extension can then be used in the same or another
module, for instance like this:If this extension is honored by the mapping, it will be mapped
to
]]>Note that the 'extension' statement itself is not mapped in any
way.As explained in , the second step
of the YANG-to-DSDL mapping takes the conceptual tree schema and
transforms it to various DSDL schemas ready for validation. As an
input parameter, this step gets in the simplest case a specification
of the NETCONF XML document type (or combination of multiple types)
that is to be validated. These document type can be for example
reply to <nc:get> or <nc:get-config>, RPC requests or
replies and notification. Other parameters further describing the
context may also be provided, such as the list of active
capabilities, features etc.In general, the second mapping step has to accomplish the
following three tasks:
Extract the part(s) of the conceptual tree schema that are
appropriate or the requested document type. For example, if a
<get> reply is to be validated, the subtree under
<nmt:top> must be selected.The schema must be accommodated to the specific encapsulating
XML elements mandated by the RPC layer. These are, for example,
<nc:rpc> and <nc:data> elements in the case of a
datastore or <en:notification> for a notification.Finally, NETMOD-specific annotations that are relevant for the
schema language of the generated schema must be mapped to
corresponding schema-language-specific rules.These three tasks are together much simpler than the first
mapping step. Presumably, they can be effectively realized
using XSL transformations .The following subsections describe the details of the second
mapping step for the individual DSDL schema languages. then contains a detailed specification for
the mapping of all NETMOD-specific annotations.With one minor exception, obtaining a validating RELAX NG
schema from the conceptual tree schema really means only taking
appropriate parts from the conceptual tree schema and assembling
them in a new RELAX NG grammar, perhaps after removing all
unwanted annotations. Depending on the XML document type that is
the target for validation (<get>/<get-config> reply,
RPC or notification) a corresponding top-level part of the grammar
MUST be added as described in the following subsections.Schemas for multiple alternative target document types can also
be easily generated by enclosing the definitions for requested
type in <rng:choice> element.In order to avoid copying identical named pattern definitions
to the output RELAX NG file, these schema-independent definition
are collected in a library file "relang-lib.rng" which is then
included by the validating RELAX NG schemas. has the listing of this library file.The minor exception mentioned above is the annotation
@nma:config, which must be observed if the target document type is
<get-config> reply. In this case, each element definition
that has this attribute with the value "false" MUST be removed
from the schema together with its descendants. See for more details.For a reply to <get> or <get-config>, the mapping
must take the part of the conceptual tree schema under the
definition of <nmt:top> and insert it in the following
grammar:
... patterns defining contents of "nmt:top" subtree ...
... named pattern definitions ...
]]>The definition for the named pattern "message-id-attribute" is
found in the library file "relaxng-lib.rng" which is included on
the second line (see ).Definitions of other named patterns MUST be copied from the
conceptual tree schema without any changes to the resulting
grammar. However, an implementation MAY choose to copy only
those definitions that are really used in the particular
output grammar.For an RPC method named "myrpc" and defined in a YANG
module with prefix "yam", the corresponding schema subtree is
identified by the definition of <nmt:rpc-method> element
whose <nmt:input> subelement has <yam:myrpc> as the
only child.The mapping must also take into account whether the target
document type in an RPC request or reply. For "yam:myrpc"
request, the resulting grammar looks as follows:
... patterns defining contents of subtree ...
... "nmt:rpc-method/nmt:input/yam:myrpc" ...
... named pattern definitions ...
]]>For "myrpc" reply, the output grammar is
... patterns defining contents of corresponding ...
... "nmt:rpc-method/nmt:output" subtree ...
... named pattern definitions ...
]]>In both cases, exact copies of named pattern definitions from
the conceptual tree schema MUST be inserted, but an
implementation MAY choose to include only those used for the
given RPC.For a notification named "mynotif" and defined in a YANG
module with prefix "yam", the corresponding schema subtree is
identified by the definition of <nmt:notification> element
that has the single child <yam:mynotif>.The resulting grammar looks as follows:
]]>The definition of the named pattern "eventTime-element" is
found in the "relaxng-lib.rng" library file.And again, exact copies of named pattern definitions from the
conceptual tree schema MUST be inserted, but an implementation
MAY choose to include only those used for the given
notification.Schematron schemas tend to be much flatter and more uniform
compared to RELAX with exactly four levels of XML hierarchy:
<sch:schema>, <sch:pattern>, <sch:rule> and
<sch:assert> or <sch:report>.In a Schematron
schema generated by the second mapping step, the basic unit of
organization is a rule represented by
the <sch:rule> element. Every rule corresponds to exactly
one element definition in the conceptual tree schema. The
mandatory @context attribute of <sch:rule> is set to the
absolute path of the corresponding element in the data tree.In the opposite direction, however, not every element
definition has a corresponding rule in the Schematron schema: only
those definitions are taken into account that are annotated with
at least one of the following NETMOD-specific annotations:
<nma:instance-identifier>, @nma:key, <nma:leafref>,
@nma:min-elements, @nma:max-elements, <nma:must>,
@nma:unique and <nma:when>.Schematron rules may be further grouped into patterns represented by the
<sch:pattern> element. The mapping uses patterns only for
discriminating between subsets of rules that belong to different
validation phases, see . Therefore, the <sch:schema>
always has exactly two <sch:pattern> children: one named
"standard" contains rules for all annotations except
<nma:instance-identifier> and <nma:leafref>, and
another named "ref-integrity" containing rules for these two
remaining annotations, i.e., referential integrity checks.Element definitions in the conceptual tree schema that appear
inside a named pattern definition (i.e., have <rng:define>
among its ancestors) are subject to a different treatment. This is
because their path in the data tree is not fixed - the named
pattern may be referred to in multiple different places. The
mapping uses abstract rules to handle
this case: An element definition inside a named pattern is mapped
to an abstract rule and every use of the named pattern then
extends this abstract pattern in the concrete context.EXAMPLE. Consider this element definition annotated with
<nma:must>:
The default-lease-time must be less than max-lease-time
]]>If this element definition appears outside any named pattern
and as a child of <dhcp:dhcp> (as it does in the DHCP
schema, see ), it is mapped to the
following Schematron rule:
The default-lease-time must be less than max-lease-time
]]>Now assume the element definition is inside a named pattern
definition, say
... same content ...
]]>In this case it is mapped to an abstract rule:
The default-lease-time must be less than max-lease-time
]]>Any use of the named pattern definition via <rng:ref
name="_dhcp__default-lease-time"/> then results in a new rule
extending the abstract one, for example
]]>Care must be taken that the value of the @context attribute in
general consists of two parts in this case: its beginning is
determined by the location of the <rng:ref> element in the
main schema tree and the rest of the path comes from the relative
position of the annotated element definition inside the named
pattern. The situation becomes even more complex when the mapping
has to deal with chained definitions of named patterns
(<rng:ref> inside <rng:define>). The @context value
then must be recursively glued together from multiple parts.The mapping from the conceptual tree schema to Schematron
proceeds in the following steps:
First, the active subtree(s) of the conceptual tree schema
must be selected depending on the requested target document
type. This procedure is identical to the RELAX NG case,
including the handling of @nma:config if
the target document type is <get-config> reply.Namespaces of all input YANG modules, together with the
namespaces of base NETCONF ("nc" prefix) or notifications ("en"
prefix) MUST be declared using the <sch:ns>
element, for example
]]>Validation phases are defined (see ) and their constituting patterns
"standard" and "ref-integrity" created.For either validation phase, the input conceptual tree schema
is scanned and element definitions with annotations relevant for
the given phase are selected and a <sch:rule> is created
for each of them. The rule is abstract if the element definition
appears inside a named pattern, see above.All annotations attached to the given element definition are
then mapped using the mapping rules specified in . The resulting <sch:assert> or
<sch:report> elements are the installed as children of the
<sch:rule> element.In certain situations it is useful to validate XML instance
documents without enforcing the referential integrity
constraints represented by the <nma:leafref> and
<nma:instance-identifier> annotations. For example, a
candidate configuration referring to configuration parameters or
state data of certain hardware will not pass full validation
before the hardware is installed. To handle this, the Schematron
mapping introduces two validation
phases:
Validation phase "full", which is the default, checks all
semantic constraints.Validation phase "noref" is the same as "full" except it
doesn't check referential integrity constraints.A parameter identifying the validation phase to use has to be
passed to the Schematron processor or otherwise both patterns
are used by default. How this is exactly done depends on the
concrete Schematron processor and is outside the scope of this
document.The validation phases are defined in Schematron by listing
the patterns that are to be applied for each phase. Therefore,
the mapping puts the rules for referential integrity checking to
a special <sch:pattern> with @id attribute set
to "ref-integrity". The rules mapped from the remaining semantic
constraints are put to another <sch:pattern> with @id
attributes set to "standard".With validation phases, the resulting Schematron schema has
the following overall structure:
... more NS declarations ...
... all rules except ref. integrity checks ...
... rules for ref. integrity checks ...
]]>In order to fully represent the semantics of YANG 'choice'
statement with "mandatory true;" substatement, the RELAX NG
grammar has to be combined with a special Schematron
rule. Consider the following module:In this module, all three leaf nodes in both case branches are
optional but because of the "mandatory true;" statement, at least
one of them must be present in a valid configuration. The 'choice'
statement from this module is mapped to the following fragment of
the conceptual tree schema:
]]>In the second case branch, the "ex4:bar" element is defined as
mandatory so that this element must be present in a valid
configuration if this branch is selected. However, the two
elements in the first branch "foo" cannot be both declared as
mandatory since each one of them alone suffices for a valid
configuration. As a result, the above RELAX NG fragment would
successfully validate configurations where none of the three leafs
elements is present.Therefore, mandatory choices, which can be recognized in the
conceptual tree schema as <rng:choice> elements that do not
have <optional> as their parent, have to be handled in a
special way: For each mandatory choice where at least one of the
cases contains more than one node, a rule MUST be present in the
"standard" pattern of the Schematron schema enforcing the presence
of at least one element from any of the cases. (RELAX NG schema
guarantees that elements from different cases cannot be mixed
together, that all mandatory nodes are present etc.).For the example module above, the Schematron rule can be as
follows:
Node(s) from at least one case of choice "foobar" must exist.
]]>DSRL is the only component of DSDL that changes the information
set of the validated XML document. While DSRL has other functions,
the YANG-to-DSDL mapping uses it only for specifying default
content. For XML instance documents based on YANG data model,
insertion of default content in general includes not only default
values for leaf elements but also containers without presence. The
following definition helps in explaining the steps needed for
generating the DSRL schema.For a given conceptual tree schema and XML instance document,
we define implicit element to be an
element that is inserted in the process of substituting the
default content, provided that its parent element exists in the
instance document.Now, let C be a conceptual tree schema and D a NETCONF instance
document. Denote R the RELAX NG schema for the document type of D,
which is generated form C and assume D is a valid XML document
with respect to R. Let P be an element appearing in D. According
to the YANG rules, an element E, which is defined as an optional
child of P in the data tree, is an implicit element if and only if
it is either
a leaf element whose definition in C has a default value
specified in the @nma:default attribute, ora container element that does not have the @nma:presence
attribute set to "true" in C and at least one of its children in
the data tree is an implicit element.Element E has to satisfy additional conditions in the following
two special cases in order to be an implicit element, regardless
of whether it is a leaf or container:
If E is defined in C inside an alternative of
<rng:choice>, then this alternative must be marked as the
default one with @nma:default-case="true" in C.If the definition of E in C carries the @nma:when attribute,
then the condition in the value of @nma:when must be true in the
context of the instance document D.In DSRL, the default content of an element is specified using
the <dsrl:default-content> element, which is a child of
<dsrl:element>. Two sibling elements of
<dsrl:default-content> determine the context for application
of the default content, see :
<dsrl:parent> element contains an XSLT pattern
specifying the parent element; the default content is applied
only if the parent element exists in the instance document.<dsrl:name> contains the XML name of the element which
is inserted together with the content of
<dsrl:default-content>.The <dsrl:parent> element is optional in a general DSRL
schema but for the purpose of the YANG-to-DSDL mapping this
element MUST be always present in order to guarantee proper
application of default content.The logic of DSRL implies that for every non-leaf element P
(implicit or not) containing at least one implicit element among
its children, the DSRL schema must provide one element map for
each implicit child element E, where the full XPath of P appears
in the <dsrl:parent> element and the name of E in
<dsrl:name>.EXAMPLE. Consider the following YANG module:The DSRL schema generated for the "get-reply" target document
type will be:/nc:rpc-reply/nc:data/ex5:outer1/nc:rpc-reply/nc:data/ex5:one2/nc:rpc-reply/nc:data/ex5:outerex5:leaf11/nc:rpc-reply/nc:data/ex5:outerex5:one2/nc:rpc-reply/nc:data/ex5:outer/ex5:oneex5:leaf22
]]>
Note that the default value for "leaf3" defined in
the YANG module is ignored, because "leaf3" represents a
non-default alternative of a choice and as such can never become
an implicit element.Since DSRL has no facilities similar to named patterns in
RELAX NG, their definitions used in the conceptual tree schema
must be expanded in all places where they are referenced.Each subsection in this section is devoted to one YANG
statement and provides the specification how the statement is
mapped to the annotated RELAX NG schema of the conceptual
tree. This is the first step of the mapping procedure, see . The subsections are sorted
alphabetically by the statement keyword.Each YANG statement is mapped to an XML fragment, typically a
single element or attribute but it may also be a larger
structure. The mapping algorithm is inherently recursive, which
means that after finishing a statement the mapping continues with
its substatements, if there are any, and a certain element of the
resulting fragment becomes the parent of other fragments resulting
from the mapping of substatements.YANG XML encoding rules translate to the following rules for
ordering multiple subelements:
Within the <nmt:rpc-methods> subtree (i.e., for RPC
input and output parameters) the order of subelements is fixed
and their definitions in the conceptual tree schema MUST follow
the order specified in the source YANG module.When
mapping the 'list' statement, all keys MUST come before any
other subelements and in the same order as they are declared in
the 'key' statement. The order of the remaining (non-key)
subelements is not specified, so their definitions in the
conceptual tree schema MUST be enclosed in the
<rng:interleave> element.Otherwise, all
definitions of subelements in the conceptual tree schema MUST be
enclosed in the <rng:interleave> element.We use the following notation:
The argument of the statement being mapped is denoted by
ARGUMENT.The element in the RELAX NG schema that becomes the parent of
the resulting XML fragment is denoted by PARENT.This statement is mapped to <rng:element> element and
ARGUMENT becomes the value of its @name attribute. The content
of <rng:element> is
]]>Substatements of the 'anyxml' statement are mapped
to additional children of the RELAX NG element definition.If the 'anyxml' statement occurs in any of the input YANG
modules, the following pattern definition MUST be added exactly
once to the RELAX NG schema as a child of the <rng:grammar>
element (cf. , p. 172):
]]>EXAMPLE: YANG statementmaps to the following fragment:Any XML content allowed here
]]>This statement is not mapped to the output schema, but see
the rules for extension handling in .As a substatement of 'uses', this statement is handled as a
part of 'uses' mapping, see .At the top level of a module or submodule, the 'augment'
statement is used for augmenting the schema tree of another YANG
module. If the latter module is not processed within the same
mapping session, the top-level 'augment' statement MUST be
ignored. Otherwise, the contents of the statement are added to
the foreign module with the namespace of the module where the
'augment' statement appears.This statement is ignored as a substatement of 'identity' and
handled within the 'identityref' type if it appears as a
substatement of that type definition, see .This statement is not used since processing of submodules
is always initiated from the main module, see .This statement is handled within the "bits" type, see .This statement is mapped to <rng:group> element. If the
argument of a sibling 'default' statement equals to ARGUMENT,
@nma:default-case attribute with the value of "true" is added to
that <rng:group> element.This statement is mapped to <rng:choice> element.Unless 'choice' has the 'mandatory' substatement with the
value of "true", the <rng:choice> element MUST be wrapped
in <rng:optional>.The 'choice' statement with "mandatory true;" requires
additional handling, see .This statement is mapped to @nma:config attribute and
ARGUMENT becomes its value.This statement is not used by the mapping since the output
RELAX NG schema may result from multiple YANG modules created by
different authors. The schema contains references to all input
modules in the Dublin Core elements <dc:source>, see . The original modules are the
authoritative sources of the authorship information.Using the procedure outlined in , the mapping algorithm MUST
determine whether the statement defines an optional container,
and if so, insert the <rng:optional> element and make it
the new PARENT.The container defined by this statement is then mapped to the
<rng:element> element, which becomes a child of PARENT and
uses ARGUMENT as the value of its @name attribute.If this statement is a substatement of 'typedef' or 'leaf',
it is mapped to the @nma:default attribute of PARENT and
ARGUMENT becomes its value.As a substatement of 'choice', the 'default' statement
identifies the default case and is handled within the 'case'
statement, see . If the default case
uses the shorthand notation where the 'case' statement is
omitted, an extra <rng:group> element MUST be inserted with
@nma:default-case attribute set to "true". The net result is
then the same as if the 'case' statement wasn't omitted for the
default case.EXAMPLE. The following 'choice' statementis mapped to
]]>This statement is ignored if it appears at the top level of
each input YANG module. The description can be found in the
source module that is referred to by Dublin Core element
<dc:source> and use ARGUMENT as its content.Otherwise, this statement is mapped to the DTD compatibility
element <a:documentation> and ARGUMENT becomes its text.In order to get properly formatted in the RELAX NG compact
syntax, this element SHOULD be inserted as the first child of
PARENT.All 'deviation' statements found in the input YANG modules MUST
be applied first so that the mapping algorithm operates on a
schema tree with all deviations already incorporated.This statement is mapped to <rng:value> element and
ARGUMENT becomes its text. All substatements except 'status' are
ignored because the <rng:value> element cannot contain
annotations, see , section 6.This statement is ignored unless it is a substatement of
'must'. In the latter case it is mapped to the
<nma:error-app-tag> element. See also .This statement is ignored unless it is a substatement of
'must'. In the latter case it is mapped to the
<nma:error-message> element. See also .This statement is ignored. However, extensions to the YANG
language MAY be mapped as described in .This statement is ignored.This statement is mapped to a RELAX NG named pattern
definition <rng:define>, but only if the grouping defined
by this statement is used without
refinements and augments in at least one of the input
modules. In this case, the named pattern definition becomes a
child of the <rng:grammar> element and its name is
ARGUMENT mangled according to the rules specified in .Whenever a grouping is used with additional refinements
and/or augments, the grouping is expanded so that the
refinements and augments may be applied directly to the
prescribed schema nodes. See for
further details and an example.An implementation MAY offer the option of recording all
'grouping' statements as named patterns in the output RELAX NG
schema even if they are not referenced. This is useful for
mapping YANG "library" modules containing only 'typedef' and/or
'grouping' statements. This statement is not specifically mapped. However, if the
identity defined by this statement is used as the base for an
"identityref" type in any of the input modules, ARGUMENT will
appear as the text of one of the <rng:value> elements in
the mapping of that "identityref" type. See for more details and an example.The information whether a given feature is available or not
MUST be supplied to the mapping procedure, which MUST modify the
YANG schema tree by including or excluding the parts that depend
on that feature.This statement is not specifically mapped. The module whose
name is in ARGUMENT has to be parsed so that the importing
module be able to use its top-level groupings and typedefs and
also augment the data tree of the imported module.If the 'import' statement has the 'revision' substatement,
the corresponding revision of the imported module MUST be
used. The mechanism for finding a given module revision is
outside the scope of this document.This statement is not specifically mapped. The submodule
whose name is in ARGUMENT has to be parsed and its contents
mapped exactly as if the submodule text was a subset of the main
module text.If the 'include' statement has the 'revision' substatement,
the corresponding revision of the submodule MUST be used. The
mechanism for finding a given submodule revision is outside the
scope of this document.This statement is handled within 'rpc' statement, see .This statement is mapped to @nma:key attribute. ARGUMENT is
MUST be translated so that every key is prefixed with the
namespace prefix of the local module. The result of this
translation then becomes the value of the @nma:key
attribute.This statement is mapped to the <rng:element> element
and ARGUMENT becomes the value of its @name attribute.The leaf is optional if there is no "mandatory true;"
substatement and if the leaf is not declared among the keys of
an enclosing list. In this case, the <rng:element> element
MUST be wrapped in <rng:optional>.This statement is mapped to a block enclosed by either
<rng:zeroOrMore> or <rng:oneOrMore> element
depending on whether the argument of 'min-elements' substatement
is "0" or positive, respectively (it is zero by default). This
<rng:zeroOrMore> or <rng:oneOrMore> element becomes
the PARENT.<rng:element> is the added as a child element of PARENT
and ARGUMENT becomes the value of its @name attribute. If the
'leaf-list' statement has the 'min-elements' substatement and
its argument is greater than one, additional attribute
@nma:min-elements is attached to <rng:element> and the
argument of 'min-elements' becomes the value of this
attribute. Similarly, if there is the 'max-elements'
substatement and its argument value is not "unbounded",
attribute @nma:max-elements is attached to this element and the
argument of 'max-elements' becomes the value of this
attribute.EXAMPLE. YANG leaf-listis mapped to the following RELAX NG fragment:
]]>This statement is handled within the "string" type, see .This statement is mapped exactly as the 'leaf-list'
statement, see .This statement may appear as a substatement of 'leaf',
'choice' or 'anyxml' statement. If ARGUMENT is "true", the
parent data node is mapped as mandatory, see .This statement is handled within 'leaf-list' or 'list'
statements, see .This statement is handled within 'leaf-list' or 'list'
statements, see .This statement is not specifically mapped except that a
<dc:source> element SHOULD be created as a child of
<rng:grammar> and contain ARGUMENT as a reference to the
input YANG module. See also .With respect to the conceptual tree schema, substatements of
'module' MUST be mapped so that
top level data elements be defined as children of the
<nmt:top> element;elements mapped from 'rpc' statements be defined as
children of the <nmt:rpc-methods> element;elements mapped from 'notification' statements be defined
as children of the <nmt:notifications> element.This statement is mapped to the <nma:must> element. It
has one mandatory attribute @assert (with no namespace), which
contains ARGUMENT transformed into a valid XPath expression (see
). The <nma:must> element may
get other subelements resulting from mapping 'error-app-tag' and
'error-message' substatements. Other substatements of 'must',
i.e., 'description' and 'reference', are ignored.EXAMPLE. YANG statementis mapped to
The default-lease-time must be less than max-lease-time
]]>This statement is mapped to @xmlns:xxx attribute of the
<rng:grammar> element where "xxx"
is the namespace prefix specified by the sibling 'prefix'
statement. ARGUMENT becomes the value of this attribute.This statement is mapped to the following subtree in the
RELAX NG schema ("yam" is the prefix of the local YANG module):
...
]]>Substatements of 'notification' are mapped under
<rng:element name="yam:ARGUMENT">.The <rng:element name="nmt:rpc-notification"> element is
a child of <rng:element name="nmt:notifications">.This statement is mapped to @nma:ordered-by attribute and
ARGUMENT becomes the value of this attribute. See for an example.This statement is not used by the mapping since the output
RELAX NG schema may result from multiple YANG modules authored
by different parties. The schema contains references to all
input modules in the Dublin Core elements <dc:source>, see
. The original modules are the
authoritative sources of the authorship information.This statement is handled within 'rpc' statement, see .This statement is handled within "leafref" type, see .This statement is handled within "string" type, see .This statement is ignored.This statement is handled within the sibling 'namespace'
statement, see , or within the
parent 'import' statement, see . As a
substatement of 'belongs-to' (in submodules), the 'prefix'
statement is ignored.This statement is mapped to the annotation attribute
@nma:presence with the value of "true". In addition, it
influences the mapping of 'container' (): the parent container definition MUST
be wrapped in <rng:optional>, regardless of its
content. See also .This statement is handled within numeric types, see .This statement is ignored if it appears at the top level of a
module or submodule.Otherwise, this statement is mapped
to <a:documentation> element and its text is set to
ARGUMENT prefixed with "See: ".This statement is handled within the types "leafref" () and "instance-identifier" ().The mapping uses only the most recent instance of the
'revision' statement, i.e., one with the latest date in
ARGUMENT, which specifies the current revision of the input YANG
module . This date SHOULD be recorded,
together with the name of the YANG module, in the corresponding
Dublin Core element <dc:source> (see ), for example in this form:
YANG module 'foo', revision 2009-01-19]]>The 'description' substatement of 'revision' is not used.This statement is mapped to the following subtree in the
RELAX NG schema ("yam" is the prefix of the local YANG module):
]]>As indicated by the comments, contents of the 'input'
substatement (if any) are mapped under <rng:element
name="yam:ARGUMENT">. Similarly, contents of the 'output'
substatement are mapped under <rng:element
name="nmt:output">. If there is no 'output' substatement, the
<rng:element name="nmt:output"> MUST NOT be present.The <rng:element name="nmt:rpc-method"> element is
a child of <rng:element name="nmt:rpc-methods">.This statement is mapped to @nma:status attribute and
ARGUMENT becomes its value.This statement is not specifically mapped. Its substatements
are mapped as if they appeared directly in the module the
submodule belongs to.Most YANG built-in types have an equivalent in the XSD
datatype library as shown in .YANG typeXSD typeMeaningint8byte8-bit integer valueint16short16-bit integer valueint32int32-bit integer valueint64long64-bit integer valueuint8unsignedByte8-bit unsigned integer valueuint16unsignedShort16-bit unsigned integer valueuint32unsignedInt32-bit unsigned integer valueuint64unsignedLong64-bit unsigned integer valuefloat32float32-bit IEEE floating-point valuefloat64double64-bit IEEE floating-point valuestringstringcharacter stringbooleanboolean"true" or "false"binarybase64Binarybinary data in base64 encodingDetails about the mapping of individual YANG built-in types
are given in the following subsections.This type is mapped to <rng:empty/>.These two built-in types do not allow any restrictions and
are mapped simply by inserting <rng:data> element whose @type
attribute is set to ARGUMENT mapped according to .This type is mapped to <rng:list> and for each 'bit'
substatement the following XML fragment is inserted as a child
of <rng:list>:bit_name
]]>where bit_name is the name of the bit as found in the
argument of the corresponding 'bit' statement.These types are mapped to <rng:choice> element.This type is mapped to <rng:choice> element with one
or more <rng:value> subelements. Each of the
<rng:value> subelements MUST have the @type attribute and
its value set to "QName". One <rng:value> subelement
with argument of the 'base' substatement as its text MUST
always be present. In addition, one <rng:value>
substatement MUST be added for each identity declared locally
or in an imported module that has the argument of the 'base'
substatement as its base identity.All namespace prefixes that are used for identities from
imported modules MUST be appropriately defined.EXAMPLE (taken from Section 7.16.3
of ). Consider the following two YANG
modules:If these two modules are imported to another module, leaf
definitionis mapped tocrypto:crypto-alg
des:des
des:des3
]]>The "crypto" and "des" prefixes will by typically defined
via attributes of the <rng:grammar> element.This type is mapped to <rng:data> element with @type
attribute set to "string". In addition, empty
<nma:instance-identifier> element MUST be inserted as a
child of PARENT.The 'require-instance' substatement, if it exists, is
mapped to the @require-instance attribute of
<nma:instance-identifier>.This type is mapped to <rng:data> element with @type
attribute set to the type of the leaf given in the argument of
'path' substatement. In addition, <nma:leafref> element
MUST be inserted as a child of PARENT. The argument value of
the 'path' substatement is set as the text of this
element.The 'require-instance' substatement, if it exists, is
mapped to the @require-instance attribute of
<nma:leafref>.YANG built-in numeric types are "int8", "int16", "int32",
"int64", "uint8", "uint16", "uint32", "uint64", "float32" and
"float64". They are mapped to <rng:data> element with
@type attribute set to ARGUMENT mapped according to .All numeric types support the 'range' restriction, which is
handled in the following way:
If the range expression consists of a single range part,
insert the pair of RELAX NG facets
...]]>
and
...]]>
Their contents are the lower and upper bound of the range
part, respectively. If the range part consists of a single
number, both "minInclusive" and "maxInclusive" facets use
this value as their content. If the lower bound is "min",
the "minInclusive" facet is omitted and if the upper bound
is "max", the "maxInclusive" facet is omitted.If the range expression has multiple parts separated by
"|", then repeat the <rng:data> element once for every
range part and wrap them all in <rng:choice>
element. Each <rng:data> element contains the
"minInclusive" and "maxInclusive" facets for one part of the
range expression as described in the previous item.For example, the 'typedef' statementappearing at the top level of the "example" module is
mapped to the following RELAX NG fragment:-637804242100
]]>This type is mapped to <rng:data> element with the
@type attribute set to "string".For the 'pattern' restriction, insert <rng:param> element
with @name attribute set to "pattern". The argument of the
'pattern' statement (regular expression) becomes the content
of this element.The 'length' restriction is handled in the same way as the
'range' restriction for the numeric types, with the additional
twist that if the length expression has multiple parts, the
"pattern" facet
...]]>
if there is any, must be repeated inside each copy of the
<rng:data> element, i.e., for each length part.If the 'type' statement refers to a derived type, it is
mapped in one of the following ways depending on whether it
contains any restrictions as its substatements:
Without restrictions, the 'type' statement is mapped
simply to the <rng:ref> element, i.e., a reference to
a named pattern. If the RELAX NG definition of this named
pattern has not been added to the output schema yet, the
corresponding 'typedef' must be found and its mapping
installed as a subelement of <rng:grammar>, see . Even if a given derived type is
used more than once in the input YANG modules, the mapping
of the corresponding 'typedef' MUST be installed only
once.If any restrictions are present, the base type for the
given derived type must be determined and the mapping of
this base type is used. Restrictions appearing at all stages
of the derivation chain must be taken into account and their
conjunction added to the <rng:data> element which
defines the basic type.See for more details and an
example.This statement is mapped to a RELAX NG named pattern
definition <rng:define>, but only if the type defined by
this statement is used without
restrictions in at least one of the input modules. In
this case, the named pattern definition becomes a child of the
<rng:grammar> element and its name is ARGUMENT mangled
according to the rules specified in .Whenever a derived type is used with additional restrictions,
the the base type for the derived type is used instead with
restrictions (facets) that are a combination of all restrictions
specified along the type derivation chain. See for further details and an example.An implementation MAY offer the option of recording all
'typedef' statements as named patterns in the output RELAX NG
schema even if they are not referenced. This is useful for
mapping YANG "library" modules containing only 'typedef' and/or
'grouping' statements.This statement is mapped to @nma:unique attribute. ARGUMENT
is translated so that every node identifier in each of its
components is prefixed with the namespace prefix of the local
module, unless the prefix is already present. The result of this
translation then becomes the value of the @nma:unique
attribute.For example, assuming that the local module prefix is
"ex",unique "foo ex:bar/baz"is mapped to the following attribute/value pair:nma:unique="ex:foo ex:bar/ex:baz"This statement is mapped to @nma:units attribute and ARGUMENT
becomes its value.If this statement has neither 'refine' nor 'augment'
substatements, it is mapped to <rng:ref> element and the
value of its @name attribute is set to ARGUMENT mangled
according to If there are any 'refine' or 'augment' substatements, the
corresponding grouping must be looked up and its contents is
inserted as children of PARENT. See for further details and an
example.This statement is ignored.This statement is mapped to @nma:when attribute and ARGUMENT
becomes it value.This statement is not mapped to the output schema. However,
an implementation SHOULD check that it is compatible with the
YANG version declared by the statement (currently
version 1).This statement is not mapped to the output schema, but see
the rules for extension handling in .This section contains mapping specification for individual
NETMOD-specific annotations. In each case, the result of the
mapping must be inserted into an appropriate context of the target
DSDL schema as described in . The
context is determined by the element definition in the conceptual
tree schema to which the annotation is attached. In the rest of
this section, we will denote CONTELEM the name of this context
element properly qualified with its namespace prefix. Unless
otherwise stated, Schematron asserts are descendants of the
"standard" pattern and therefore active in both validation
phases.This annotation MUST be observed when generating any schema
for the reply to <nc:get-config>. In particular:
When generating RELAX NG, the contents of the CONTELEM
definition MUST be changed to <rng:notAllowed>.When generating Schematron or DSRL, the CONTELEM
definition and all its descendants in the conceptual tree
schema MUST be ignored.This annotation is used for generating the DSRL schema as
described in .This annotation is used for generating the DSRL schema as
described in .This annotation currently has no mapping defined.This annotation is handled within <nma:must>, see .If this annotation element has the @require-instance
attribute with the value "false", it is ignored. Otherwise it is
mapped to the following Schematron assert:
The element pointed to by "CONTELEM" must exist.
]]>The nmf:evaluate() function is an XSLT extension function
(see Extension
Functions in ) that evaluates an
XPath expression at runtime. Such an extension function is
provided by some XSLT processors, for example Saxon.Assume this annotation has the value "k_1 k_2 ... k_n", i.e.,
specifies n child leaves as keys. The annotation is then mapped
to the following Schematron report:
Duplicate key of list "CONTELEM"
]]>where CONDITION has this form:preceding-sibling::CONTELEM[C_1 and C_2 and ... and C_n]Each C_i, for i=1,2,...,n, specifies the condition for
violation of uniqueness of key k_i, namely
k_i=current()/k_iThe mapping of this annotation depends on its
@require-instance attribute. If this attribute is not present or
its value is "true", the referred leaf must exist in the
instance document (this is verified by the RELAX NG schema) and
the <nma:leafref> annotation is mapped to the following
assert:
Leafref "CONTELEM" must have the same value as "PATH"
]]>where PATH is the content of <nma:leafref>.If the @require-instance attribute has the value "false", then
the equality in contents of the context element and the referred
leaf is required only if the referred leaf exists. Hence,
<nma:leafref> is mapped to the following assert:
Leafref "CONTELEM" must have the same value as "PATH"
]]>In both cases the assert is a descendant of the
"ref-integrity" pattern, which means that it will be used only
for the "full" validation phase.This annotation is mapped to the following Schematron
assert:
List "CONTELEM" - item count must be at least MIN
]]>where MIN is the value of @nma:min-elements.This annotation is mapped to the following Schematron
assert:
List "CONTELEM" - item count must be at most MAX
]]>where MAX is the value of @nma:min-elements.This annotation is mapped to the following Schematron
assert:
MESSAGE
]]>where EXPRESSION is the value of the mandatory @assert
attribute of <nma:must>. If the <nma:error-message>
subelement exists, MESSAGE is set to its content, otherwise it
is set to the default message "Condition EXPRESSION must be
true".This annotation currently has no mapping defined.This annotation currently has no mapping defined.The mapping of this annotation is almost identical as for
@nma:key, see , with two small
differences:
The value of @nma:unique is a list of descendant schema node
identifiers rather than simple leaf names. However, the XPath
expressions specified in work without
any modifications if the descendant schema node identifiers
are substituted for k_1, k_2, ..., k_n.The message appearing as the text of <sch:report> is
different: "Violated uniqueness for list CONTELEM".This annotation is mapped to the following Schematron assert:
Node "CONTELEM" is only valid if "EXPRESSION" is true.
]]>where EXPRESSION is the value of @nma:when.This document registers two namespace URIs in the IETF XML
registry :URI: urn:ietf:params:xml:ns:netmod:dsdl-annotations:1URI: urn:ietf:params:xml:ns:netmod:conceptual-tree:1Extensible Markup Language (XML) 1.0 (Fourth Edition)XML Schema Part 1: Structures Second EditionXML Schema Part 2: Datatypes Second EditionYANG - A data modeling language for NETCONFKey words for use in RFCs to
Indicate Requirement LevelsSimple Network Management Protocol (SNMP)Simple Network Management Protocol (SNMP)
ResearchPerformance Systems InternationalPerformance Systems InternationalMassachusetts Institute of Technology (MIT),
Laboratory for Computer ScienceNETCONF Event NotificationsXSL Transformations (XSLT) Version 1.0RELAX NG DTD CompatibilityXML Path Language (XPath) Version 1.0SMIng ObjectivesNETCONF Configuration ProtocolThe Dublin Core Metadata Element SetDocument Schema Definition Languages (DSDL) - Part 1:
OverviewISO/IECInformation Technology - Document Schema Definition
Languages (DSDL) - Part 2: Regular-Grammar-Based Validation -
RELAX NG. Second Edition.ISO/IECInformation Technology - Document Schema Definition
Languages (DSDL) - Part 2: Regular-Grammar-Based Validation -
RELAX NG. AMENDMENT 1: Compact SyntaxISO/IECInformation Technology - Document Schema Definition
Languages (DSDL) - Part 3: Rule-Based Validation -
SchematronISO/IECInformation Technology - Document Schema Definition
Languages (DSDL) - Part 8: Document Semantics Renaming
Language - DSRLISO/IECThe IETF XML RegistryStructure of Management Information
Version 2 (SMIv2)Cisco Systems, Inc.SNMPinfoTU BraunschweigCommon YANG Data TypesRELAX NGThis appendix contains the RELAX NG schema for the
NETMOD-specific annotations in both XML and compact syntax.[Editor's note: It is currently only a set of named pattern
definitions as templates for the annotation elements and
attributes. We should find a way how to connect this to the schema
for RELAX NG, which these annotations extend. One option may be
NVDL or it can also be done as in the spec for DTD compatibility
annotations.]usersystemtruecurrentdeprecatedobsolete
]]>In order to avoid copying the same named pattern definitions to
the RELAX NG schemas generated in the second mapping step, we
collected these definitions to a library file - schema-independent
library - which is included by the validating schemas under the
file name "relaxng-lib.rng" (XML syntax) and "relaxng-lib.rnc"
(compact syntax). The included definitions cover patterns for
common elements from base NETCONF and
event notifications .
4095
]]>This appendix demonstrates both steps of the
YANG-to-DSDL mapping applied to the "canonical" DHCP
tutorial data model. The input (single) YANG module is
shown in and the output schemas in
the following two subsections.The conceptual tree schema was obtained by the "rng" plugin of
the pyang
tool and the validating DSDL schemas by XSLT stylesheets that are
also part of pyang distribution. RELAX NG schemas are shown in
both XML and compact syntax. The latter was obtained from the
former by using the Trang
toolDue to the limit of 72 characters per line, few long strings
required manual editing, in particular the regular expression
patterns for IP addresses etc. in the RELAX NG schemas. In the
compact syntax we broke the patterns to appropriate segments and
joined them with the concatenation operator "~". In the XML
syntax, though, the long patterns had to be replaced by the
placeholder string "... regex pattern ...". Also, line breaks were
added to several documentation strings and Schematron
messages. Other than that, the results of the automatic
translations were not changed.Pyang 0.9.3, RELAX NG pluginYANG module 'dhcp'
configuration and operational parameters for a DHCP server.
The default-lease-time must be less than max-lease-time
ethernettoken-ringfddiA reusable list of subnets
Allows BOOTP clients to get addresses in this range
Options in the DHCP protocol
See: RFC 2132, sec. 3.8
See: RFC 2132, sec. 3.17
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
]]>
> nma:must [
assert = ". <= ../dhcp:max-lease-time"
nma:error-message [
"The default-lease-time must be less than max-lease-time"
]
]
}?,
_dhcp__subnet-list,
element dhcp:shared-networks {
[ nma:key = "dhcp:name" ]
element dhcp:shared-network {
element dhcp:name { xsd:string },
_dhcp__subnet-list
}*
}?,
[ nma:config = "false" ]
element dhcp:status {
[ nma:key = "dhcp:address" ]
element dhcp:leases {
element dhcp:address { inet-types__ip-address },
element dhcp:starts { yang-types__date-and-time }?,
element dhcp:ends { yang-types__date-and-time }?,
element dhcp:hardware {
element dhcp:type { "ethernet"
| "token-ring"
| "fddi"
}?,
element dhcp:address { yang-types__phys-address }?
}?
}*
}?
}?
},
element nmt:rpc-methods { empty },
element nmt:notifications { empty }
}
## A reusable list of subnets
_dhcp__subnet-list =
[ nma:key = "dhcp:net" ]
element dhcp:subnet {
element dhcp:net { inet-types__ip-prefix },
element dhcp:range {
## Allows BOOTP clients to get addresses in this range
element dhcp:dynamic-bootp { empty }?,
element dhcp:low { inet-types__ip-address },
element dhcp:high { inet-types__ip-address }
}?,
## Options in the DHCP protocol
element dhcp:dhcp-options {
## See: RFC 2132, sec. 3.8
[ nma:ordered-by = "user" ]
element dhcp:router { inet-types__host }*,
## See: RFC 2132, sec. 3.17
element dhcp:domain-name { inet-types__domain-name }?
}?,
[ nma:default = "7200" nma:units = "seconds" ]
element dhcp:max-lease-time { xsd:unsignedInt }?
}*
inet-types__ip-prefix =
inet-types__ipv4-prefix | inet-types__ipv6-prefix
inet-types__ipv4-prefix =
xsd:string {
pattern =
"(([0-1]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.)" ~
"{3}([0-1]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])/\p{N}+"
}
inet-types__ipv6-prefix =
xsd:string {
pattern =
"((([0-9a-fA-F]{1,4}:){7})([0-9a-fA-F]{1,4})/" ~
"\p{N}+)|((([0-9a-fA-F]{1,4}:){6})(([0-9]{1,3}\." ~
"[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))/\p{N}+)|" ~
"((([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*(::)" ~
"(([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*/\p{N}+)" ~
"((([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*(::)" ~
"(([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*(([0-9]" ~
"{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))/\p{N}+)"
}
inet-types__ip-address =
inet-types__ipv4-address | inet-types__ipv6-address
inet-types__ipv4-address =
xsd:string {
pattern =
"(([0-1]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.){3}([0-1]?" ~
"[0-9]?[0-9]|2[0-4][0-9]|25[0-5])(%[\p{N}\p{L}]+)?"
}
inet-types__ipv6-address =
xsd:string {
pattern =
"((([0-9a-fA-F]{1,4}:){7})([0-9a-fA-F]{1,4})(%[\p{N}" ~
"\p{L}]+)?)|((([0-9a-fA-F]{1,4}:){6})(([0-9]{1,3}\." ~
"[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))(%[\p{N}\p{L}]+)?)|" ~
"((([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*(::)" ~
"(([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*(%[\p{N}" ~
"\p{L}]+)?)((([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*" ~
"(::)(([0-9a-fA-F]{1,4}:)*([0-9a-fA-F]{1,4}))*(([0-9]{1,3}" ~
"\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))(%[\p{N}\p{L}]+)?)"
}
inet-types__host = inet-types__ip-address | inet-types__domain-name
inet-types__domain-name =
xsd:string {
pattern =
"([a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9]\.)*" ~
"[a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9]"
pattern =
"([r-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9]\.)*" ~
"[a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9]"
}
yang-types__date-and-time =
xsd:string {
pattern =
"\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}" ~
"(\.d*)?(Z|(\+|-)\d{2}:\d{2})"
}
yang-types__phys-address = xsd:string
]]>This appendix contains DSDL schemas that were obtained from the
conceptual tree schema in by XSL
transformations. These schemas can be directly used for validating
a reply to unfiltered <get> with the contents corresponding
to the DHCP data model.The RELAX NG schema (again shown in both XML and compact
syntax) includes the schema independent library from .ethernettoken-ringfddi
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
... regex pattern ...
]]>
Duplicate key of list dhcp:subnet
The default-lease-time must be less than max-lease-time
Duplicate key of list dhcp:shared-network
Duplicate key of list dhcp:leases
]]>/nc:rpc-reply/nc:data/dhcp:dhcp7200600/nc:rpc-reply/nc:data/dhcp:dhcpdhcp:max-lease-time7200/nc:rpc-reply/nc:data/dhcp:dhcpdhcp:default-lease-time600
/nc:rpc-reply/nc:data/dhcp:dhcp/dhcp:subnet
dhcp:max-lease-time7200
/nc:rpc-reply/nc:data/dhcp:dhcp/dhcp:shared-networks/
dhcp:shared-network/dhcp:subnet
dhcp:max-lease-time7200
]]>
Moved "NETCONF Content
Validation" after .New text about mapping defaults to DSRL, especially in
and .Finished the DHCP example by adding the DSRL schema to
.New @nma:presence annotation was added - it is needed for
proper handling of default content. "Constraints on Mandatory
Choice" was added because these constraints require a
combination of RELAX NG and Schematron.Fixed the schema for NETMOD-specific annotations by adding
explicit prefix to all defined elements and
attributes. Previously, the attributes had no namespace.Handling of 'feature', 'if-feature' and 'deviation'
added.Handling of nma:instance-identifier via XSLT extension
function.Many other minor corrections and improvements.Attributes @nma:min-elements and @nma:max-elements are
attached to <rng:element> (list entry) and not to
<rng:zeroOrMore> or <rng:oneOrMore>.Keys and all node identifiers in 'key' and 'unique'
statements are prefixed.Fixed the mapping of 'rpc' and 'notification'.Removed previous sec. 7.5 "RPC Signatures and
Notifications" - the same information is now contained in
and .Added initial "_" to mangled names of groupings.Mandated the use of @xmlns:xxx as the only method for
declaring the target namespace.Added section "Handling of XML Namespaces" to explain the
previous item.Completed DHCP example in .Almost all text about the second mapping step is new.