XSchema Spec, Section 1.0 (Draft 1)
SimonStL at classic.msn.com
Sun Jun 7 15:36:59 BST 1998
Below is a initial draft of section 1.0 of the XSchema specification. This
section provides an introduction to the XSchema specification, describing its
relationship to standards, the goals developed earlier on this mailing list,
and providing a glossary for terminology. The glossary is not yet developed,
but will certainly grow as the specification progresses.
Let's _not_ reopen the goals, please, but other comments and suggestions are
welcome. I hope to have some of section 2.0 (the real guts of the spec) up
Sunday or Monday.
A prettier version (formatted using HTML) is available at
Dynamic HTML: A Primer / XML: A Primer / Cookies
Extensible Markup Language (XML) uses notation inherited from the Standard
Generalized Markup Language (SGML) to represent document structures and
inclusions in its Document Type Definitions (DTDs). While this achieves
considerable compatibility with SGML, it makes it impossible to extend the
capacities of a DTD beyond those provided in SGML, requires developers to
understand two different syntaxes for documents and DTDs, and forces tool
builders to create a separate set of tools for managing DTDs.
This XSchema specification describes an XML document representation for the
structural information currently represented by DTDs, and a transformation
from XSchema documents to DTDs. This specification also suggests mechanisms
and processing models for connecting documents to XSchemas.
This initial version of the XSchema specification is deliberately simple,
providing an initial base for implementations while introducing as few
complicating factors as possible. Authors accustomed to DTD creation may find
their toolset constricted; it is hoped that supporting software and tools
available from other standards will make up for this reduced toolset.
The XSchema specification is the product of discussions on the xml-dev mailing
list. This document has no official status. The editors have no affiliation
with the World Wide Web Consortium (W3C), the organization developing and
maintaining the XML standard, nor any affiliation with any W3C member
organizations. While it is hoped that this document may eventually be
submitted to the W3C as a Note, it is not an official specification and should
be considered experimental.
1.2 Origin and Goals
Proposals for describing SGML document type definitions using document syntax
rather than the separate declaration syntax have been under development for a
number of years, and used by several tools for documentation. The current
proposal arose from a number of concerns surrounding XML's usability and
consistency. Originally conceived of as a mapping of DTD syntax to document
syntax, the project has focused more on creating schemas describing element
and attribute structures rather than preserving every function provided by XML
The list of goals developed by the xml-dev discussion follows:
1. XSchema documents shall use XML document syntax, using element nesting and
attributes to describe all constraints that may be verified by a processor
using XSchema .
2. XSchema shall define a transformation from XSchema documents to DTDs.
3. XSchema documents shall be capable of representing the normalized element
and attribute structures defined in XML 1.0 DTDs, and provide namespace
4. XSchema documents shall be parseable, manageable, and manipulable using the
same tools used to parse, manage, and manipulate XML documents.
5. XSchema documents shall be easy to create, read, and modify, and shall
provide authoring support for XML documents.
6. XSchema documents shall be easy to use in combination with a parser to
provide structural validation of documents.
7. XSchema shall include an XSchema document and an XML 1.0 DTD defining the
structure of XSchema documents .
8. XSchema shall suggest mechanisms for applying XSchema documents to
9. XSchema shall include mechanisms for extending the information included in
XSchema documents to support metadata.
10. The XSchema specification shall be readable, clear, and rigorous, using
terminology and nomenclature as close to the XML 1.0 specification as
11. The XSchema specification will comply with and be consistent with W3C
12. XSchema documents shall provide constructs for human- and machine-readable
1.3 Relation to Standards
XSchemas use XML 1.0 document instance syntax and may be applied to XML 1.0
documents. XSchemas are also designed to make use of XML namespaces. It is
hoped that XSchemas and RDF Schemas may be mapped to each other. This
specification has also been influenced by the discussion of the XML-Data
proposal made to the W3C on 5 January, 1998.
may - XSchemas are permitted but not required to behave as described.
must - XSchemas must behave as described. Failure to behave as described
constitutes an error.
error - A breach of the rules set forth in this specification. Software
should report this error to the user.
[to be filled in as the specification develops.]
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