YANG2DSDL(1)

NAME
yang2dsdl - translates YANG data models to DSDL schemas and validates instance documents.

SYNOPSIS

yang2dsdl [-t target] [-d dir] [-b basename] [-j] [-x] [-c] [-v instance] file...

yang2dsdl -L [-t target] [-d dir] [-b basename] [-j] [-x] [-c] [-v instance] file

yang2dsdl -s [-t target] [-d dir] -b basename [-j] [-x] [-c] -v instance

yang2dsdl -h

DESCRIPTION

This shell script facilitates the translation of a data model described by one or more input YANG modules to DSDL schemas (RELAX NG, Schematron and DSRL) for a selected instance XML document type, as described in RFC 6110[1]. Optionally, the script can validate an instance document of the given type against the schemas.

The input YANG module(s) may be given either directly as file parameter(s) on the command line, or indirectly through a server <hello> message which also declares capabilities and features supported by the server. The latter alternative is indicated by the -L switch, and only one file parameter may be given in this case.

Input YANG module(s) may be expressed in YANG or YIN syntax. The output DSDL schemas are written to the directory dir (current directory by default). Unless the option -s is used, this directory must be writable.

Metadata annotations are also supported, if they are defined and used as described in RFC 7952[2].

The script can be executed by any shell interpreter compatible with POSIX.2, such as bash(1) or dash(1).

The target argument specifies the type of the target instance document. Supported values are:

data
    Datastore contents (configuration and state data) encapsulated in <nc:data> document element.

config
    A configuration datastore contents encapsulated in <nc:config> document element.

get-reply
    A complete NETCONF message containing a reply to the <nc:get> operation.

get-data-reply
    A complete NETCONF message containing a reply to the <ncds:get-data> operation.

get-config-reply
    A complete NETCONF message containing a reply to the <nc:get-config> operation.

edit-config
    A complete NETCONF message containing an <nc:edit-config> request. Only the RELAX NG schema is generated for this target.

rpc
    An RPC request defined in an input YANG module.

rpc-reply
    An RPC reply defined in an input YANG module.

notification
    An event notification defined in an input YANG module.

The output schemas are contained in the following four files whose names depend on the arguments basename and target:

basename-target.rng
    RELAX NG schema for the target document type.

basename-gdefs-config.rng, basename-gdefs-edit.rng, basename-gdefs.rng
    Auxiliary RELAX NG schema containing global named pattern definitions. The first is generated for "config" and "get-config-reply" targets, the second for "edit-config" and the third for the remaining targets.

basename-target.sch
    Schematron schema for the target document type. Not generated for the "edit-config" target.

basename-target.dsrl
    DSRL schema for the target document type. Not generated for the "edit-config" target.

Optional validation of an XML document stored in the file instance proceeds as follows:

    1. Grammatical and datatype constraints are checked using the RELAX NG schema.

    2. The DSRL schema is used for adding default values together with ancestor containers to the instance document where necessary.

    3. Semantic constraints are checked using the Schematron schema. The skeleton implementation of ISO Schematron[3] by Rick Jelliffe is included in the distribution and used for this purpose.

Steps 2 and 3 are not performed for the "edit-config" target, or if step 1 reports any errors.

Option -s may be used together with -v for validating an instance document without generating the schemas. This assumes that the schemas are already present in the directory selected by the -d option (current directory by default). In this case, the basename of the schemas must be specified using -bbasename and the input YANG modules need not be given. Also, if the DSRL or Schematron schema is missing, the corresponding step is skipped.

The script uses programs from the libxml2 suite - xmllint(1) for RELAX NG validation and xsltproc(1) for performing XSLT transformations. Alternatively, jing(1) can be used for RELAX NG validation (option -j). If necessary, the script could be easily modified for use with other RELAX NG validators and/or XSLT1 processors supporting EXSLT.

OPTIONS

-b basename
    Specifies the basename of files in which the output schemas are stored. The default is the concatenation of the names of all input YANG modules connected with the underscore character "_". This option is mandatory if -s is used.

-d dir
    Specifies the directory for output files. By default they are stored in the current directory.

-h
    Displays help screen and exits.

-j
    Uses jing(1) for RELAX NG validation instead of the default xmllint(1).

-L
    Interpret the file parameter as the name of a file containing a server <hello> message. In this case, exactly one file parameter must be given.

-s
    Performs just validation, without (re)generating the schemas. This option is only allowed together with -v and -bbasename must also be specified.

-t target
    Specifies the target XML document type using one of the following strings as explained above: data (default), config, get-reply, get-data-reply, get-config-reply, edit-config, rpc, rpc-reply or notification.

-v instance
    Validates an instance XML document contained in file instance.

-x
    Try to translate modules written in unsupported YANG versions. If the module doesn't use any constructs introduced after YANG version 1, this may work. This option may produce unexpected results. Use at own risk.

-c
    Use only definitions with status "current" in the YANG module.

FILES

/usr/local/share/yang/xslt/gen-relaxng.xsl
    XSLT stylesheet generating RELAX NG schemas.

/usr/local/share/yang/xslt/gen-schematron.xsl
    XSLT stylesheet generating Schematron schemas.

/usr/local/share/yang/xslt/gen-dsrl.xsl
    XSLT stylesheet generating DSRL schemas.

/usr/local/share/yang/xslt/gen-common.xsl
    Common templates for all three XSLT generators.

/usr/local/share/yang/xslt/dsrl2xslt.xsl
    Translates a subset of DSRL containing only specification of default contents to an XSLT stylesheet.

/usr/local/share/yang/xslt/svrl2text.xsl
    Translates an SVRL report to plain text.

/usr/local/share/yang/schema/relaxng-lib.rng
    RELAX NG library of common NETCONF elements.

/usr/local/share/yang/schema/edit-config-attributes.rng
    RELAX NG definitions of <edit-config> attributes.

ENVIRONMENT VARIABLES

PYANG_XSLT_DIR
    Alternative directory for XSLT stylesheets. The default is installation dependent.

PYANG_RNG_LIBDIR
    Alternative directory for the RELAX NG library. The default is installation dependent.

XSLT_OPTS
    Options to pass to the XSLT processor when generating the DSDL schemas. This is mainly useful for debugging.

EXAMPLES

    $ yang2dsdl -v dhcp-data.xml dhcp.yang

This command generates the DSDL schemas for the datastore contents (default data target) as defined by the dhcp.yang module and validates an instance document stored in the dhcp-data.xml file.

    $ yang2dsdl -t rpc rpc-rock.yang

This command generates DSDL schemas for the choice of input parts (requests) of all RPC operations defined in the module rpc-rock.yang.

DIAGNOSTICS

yang2dsdl return codes have the following meaning:

0
    No error (normal termination)

1
    Error in input parameters

2
    Error in DSDL schema generation

3
    Instance validation failed

BUGS

    1. The logic of command-line arguments may not be able to distinguish replies to different RPC requests, for example if the replies have the same top-level element.

SEE ALSO

pyang(1), xsltproc(1), xmllint(1), RFC 6110[1], DSDL[4], RELAX NG[5], ISO Schematron[3].

AUTHOR

Ladislav Lhotka <lhotka@nic.cz>
CZ.NIC

NOTES

1.  RFC 6110
    http://tools.ietf.org/html/rfc6110

2.  RFC 7952
    http://tools.ietf.org/html/rfc7952

3.  ISO Schematron
    http://www.schematron.com

4.  DSDL
    http://www.dsdl.org/

5.  RELAX NG
    http://www.relaxng.org/