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Wednesday, March 12, 2008

Defining NETCONF Data Models using Document Schema Definition Languages

Members of the IETF Network Configuration (NETCONF) Working Group have
published an updated draft for the specification "Defining NETCONF Data
Models using Document Schema Definition Languages (DSDL)." The document
describes a concrete proposal for creating Netconf and other IETF data
models using the RelaxNG schema language and the Schematron validation
language, which are both part of ISO's Document Schema Definition
Languages (DSDL) standard. Appendix D preents the DHCP schema in Relax
XML format For those who prefer the XML syntax of Relax NG, the
"dhcp.rnc" file was converted to "dhcp.rng" using Trang. 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 to model
its data. The approach to data modeling described in this Internet Draft
uses the two most mature parts of the ISO Document Schema Definition
Languages (DSDL) multi-part standard: Relax NG and Schematron. The
proposal then goes on to define additional processing and documentation
annotation schema. Relax NG is a mature, traditional schema language
for validating the structure of an XML document. Schematron is a
rule-based schema validation language which uses XPath expressions to
validate content and relational constraints. In addition, this document
defines and reuses various annotation schema which can provide additional
metadata about specific elements in the data model such as textual
descriptions, default values, relational integrity key definitions,
and whether data is configuration or status data. This combination
was created to specifically address a set of Netconf-specific modeling
requirements, and in addition should be useful as a general purpose
data modeling solution useful for other IETF working groups. The
authors believe that reusing schema work being developed and used by
other standards bodies provides substantial long-term benefits to the
IETF management community, so this proposal attempts to reuse as much
existing work as possible.

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