 | Level: Intermediate Contributors: ISO 06 Feb 2007
Updated 25 Apr 2007 Document Schema Definition Languages (DSDL) is a framework
approach to XML validation and core processing comprising individual
specifications from expert individuals or small groups, each of which
addresses a well-defined and well-bounded problem domain. Discover the
parts of DSDL, including RELAX NG and Schematron, that already have
traction on their own, and the ones that are still works in progress.
Document Schema Definition
Languages (DSDL)
[ISO Draft Standards and Standards of ISO/IEC
JTC 1 SC 34 WG 1] is a collection of specifications related to the
validation and basic document composition of XML. The insight behind
DSDL is that you can approach XML validation and core processing in
numerous ways, and that many of these ways are complementary. Rather
than create one giant system covering all this capability, DSDL creates
a framework of standards that you can use separately or together for XML
validation. In this way, it avoids rigid complexity within each
specification while providing the power to address complex problems.
DSDL has 10 parts, which are listed here:
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Part 1: Interoperability framework: This part is a formal
roadmap and outline of DSDL as a whole.
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Part 2: Grammar-based validation: This part is ISO RELAX NG.
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Part 3: Rule-based validation: This part is ISO Schematron.
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Part 4: Selection of validation candidates: This part is
Namespace-based Validation Dispatching
Language (NVDL), a means of splitting up documents comprising
multiple vocabularies so that you can validate them more easily. There
have been many inputs to this part, but James Clark's Namespace Routing
Language (NRL) is the main input to the process.
-
Part 5: Datatypes: This part is a framework for creating
new primitive data types. Jeni Tennison's Datatype Library
Language is an input. It defines an XML language for defining
regular expressions for the lexical representation of new types. This
much alone is provided for (to some extent) in the facet mechanisms in
W3C XML Schema (WXS), but the important
distinction in DSDL Part 5 is that it adds a mechanism for mapping these
new data types to the value space, which is not possible in WXS. In
effect, it allows you to specify semantics as well as syntax of new data
types, which is essential.
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Part 6: Path-based integrity constraints: The goal of this
part is to define features similar to WXS's
xs:unique, xs:key, and
xs:keyref.
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Part 7: Character repertoire validation: The goal of this
part is to develop a language that allows schema designers to constrain
the character sets that they can use in various lexical structures in
XML. There are ways to express some such restrictions at present in
RELAX NG, but they break down when trying to apply such restrictions in
cases such as mixed content. Part 7 would work, for example, by allowing
one to express the constraint that "element and attribute names as well
as PI targets to be basic Latin-1" or "numbers must not appear in
element and attribute names."
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Part 8: Declarative document
manipulation: This part is a means to define patterns that can be
expressed in more than one actual XML syntax, based on a powerful schema
technology called Architectural Forms.
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Part 9: Datatype- and namespace-aware DTDs: This part
makes DTDs more useful in the face of recent developments in the XML
space by adding features more common in more recent schema
languages.
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Part 10: Validation management: This part is meant to be
the glue to allow you combine different parts from DSDL. It provides a
pipeline framework for preprocessing and validation of documents.
Resources
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