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Rohan Mahy Sharon Chisholm Lada Lhotka IETF 72 - Dublin. Representing Netconf Data Models using Document Schema Definition Languages (DSDL). Outline. What is DSDL? Scope of DSDL for NETCONF Overview Drafts Vocabularies Used Next Steps Open Issues. What is DSDL?.

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Rohan mahy sharon chisholm lada lhotka ietf 72 dublin

Rohan Mahy

Sharon Chisholm

Lada Lhotka

IETF 72 - Dublin

Representing NetconfData Models using Document Schema Definition Languages (DSDL)


What is DSDL?

Scope of DSDL for NETCONF



Vocabularies Used

Next Steps

Open Issues

What is dsdl
What is DSDL?

DSDL = Document Schema Definition Languages (‏

Family of standards ISO/IEC 19757

DSDL uses a modular approach to schema languages

Part 1: Overview

Part 2: RELAX NG – regular-grammar-based validation

Part 3: Schematron – rule-based validation

Part 4: NVDL – Namespace-based Validation Language

Part 5: DTLL – Data Type Library Language

Part 6: Path-based integrity constraints

Part 7: CRDL – Character Repertoire Description Language

Part 8: DSRL – Document Schema Renaming Language

Part 9: Datatype- and Namespace-aware DTDs

Part 10: Validation management

Scope of dsdl for netconf
Scope of DSDL for NETCONF

NETMOD Requirements

(as determined by WG)‏

Vanilla DSDL

Human-friendly Language


Tool-friendly Language


The goal is a theoretical two-way mapping of features, and a real non-lossy one-way mapping.


A layered approach leveraging existing DSDL technologies

Off-the-shelf tools/libraries can be immediately used for validation, instance editing and transformations (XSLT)‏

The smarter the tool/library, the more semantics can be validated or processed but even baseline tools can do useful work

The mapping uses 3 parts of the DSDL standard (ISO/IEC 19757), two standard annotation vocabularies and several new NETMOD-specific annotations

A software tool is available that translates most of YANG semantics

Output is an annotated RELAX NG schema

Draft mahy canmod dsdl 02

  • Reworked to fit into NETMOD framework, rather then as a proposal to CANMOD BOF

  • Made some tweaks to make mapping from yang easier (infoType, for example)

  • Started section mapping to yang;

    • As yang is a moving target, does not go into excruciating detail yet.

    • Points to –lhotka for container mapping

    • Identified some points requiring NETMOD-level discussion

      • Most of which have been raised on mailing list; rest coming soon

Draft lhotka yang dsdl map 00

New individual draft summarizing the experience from implementing YANG->DSDL translator – plugin for pyang application

Very complementary to -mahy draft

It tries to formulate principles that the WG mapping draft should state

It contains a section describing mapping details for each YANG statement.

Vocabularies used
Vocabularies Used

RELAX NG – grammatic constraints, datatypes

Schematron – semantic constraints, user-specified rules (must statement in YANG)‏

DSRL – default values of leaf nodes

Dublin Core terms – module metadata (author, revision, ...)‏

RELAX NG DTD compatibility annotations – YANG description and reference.

NETMOD-specific annotations – few new attributes attached to RELAX NG <element>.

Next steps
Next Steps

The implementation revealed several issues that have to be resolved (preferable in Dublin); some of them may require changes or clarifications in YANG.

Finish the chartered DSDL mapping draft (due in September 08). It will be based on merging two existing individual drafts:



Update the implementation:

alignment with the draft

implement mappings of YANG extension mechanisms

Major open issues
Major Open Issues

Handling of rpc and notification

YANG allows multiple root nodes, XML just one.

(For a complete list of issues, visit the NETMOD session on Friday)‏

Rpc and notification
rpc and notification

YANG modules describe the contents of agent configuration datastores, with two exceptions:

rpc specifies signature of a new NETCONF RPC method.

notification defines a NETCONF notification.


Generate separate schemas for the configuration data tree, RPCs and notifications.

Work with a „conceptual tree“ that harbors the three types of content in different subtrees.

Multiple Root Nodes

YANG allows for multiple root nodes, but well-formed XML document must have exactly one.


  • Remove this possibility from YANG

  • „conceptual tree“ (again) – multiple root nodes of the YANG module will appear under an artificial root node.


Conceptual tree

Example conceptual tree

<nmt:netmod-module xmlns:nmt=“...“>


...main configuration data tree...









Example Conceptual Tree