Representing Netconf Data Models using Document Schema Definition Languages (DSDL)

1
Representing Netconf Data Models using Document
Schema Definition Languages (DSDL) 

• Rohan Mahy
• Sharon Chisholm
• Lada Lhotka
• IETF 72 - Dublin

2
Outline

• What is DSDL?
• Scope of DSDL for NETCONF
• Overview
• Drafts
• Vocabularies Used
• Next Steps
• Open Issues

3
What is DSDL?

• DSDL Document Schema Definition Languages
  (http//www.dsdl.org)?
• 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

4
Scope of DSDL for NETCONF
NETMOD Requirements (as determined by WG)?
Vanilla DSDL
Human-friendly Language (Yang)?
Tool-friendly Language (DSDL for NETCONF)?
The goal is a theoretical two-way mapping of
features, and a real non-lossy one-way mapping.
5
Overview

• 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

6
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

7
draft-lhotka-yang-dsdl-map-00

• New individual draft summarizing the experience
  from implementing YANG-gtDSDL 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.

8
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 ltelementgt.

9
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
• draft-mahy-canmod-dsdl-02
• draft-lhotka-yang-dsdl-map-00
• Update the implementation
• alignment with the draft
• implement mappings of YANG extension mechanisms

10
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)?

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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.
• Options
• 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.

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Multiple Root Nodes

• YANG allows for multiple root nodes, but
  well-formed XML document must have exactly one.
• Options
• Remove this possibility from YANG
• conceptual tree (again) multiple root nodes
  of the YANG module will appear under an
  artificial root node.

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Backup

• Conceptual tree

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Example Conceptual Tree

• ltnmtnetmod-module xmlnsnmt...gt
• ltnmtmaingt
• ...main configuration data tree...
• lt/nmtmaingt
• ltnmtrpcsgt
• ...rpcs...
• ltnmtrpcsgt
• ltnmtnotificationsgt
• ...notifications...
• lt/nmtnotificationsgt
• lt/nmtnetmod-modulegt