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   XSD: Proposed Goals, Rev. 3

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  • From: "Simon St.Laurent" <SimonStL@classic.msn.com>
  • To: "Xml-Dev (E-mail)" <xml-dev@ic.ac.uk>
  • Date: Thu, 28 May 98 15:56:37 UT

A revised set of goals for XSD follows, based on public and private comments.  

These are still open to change until Friday.  If there are changes today, I'll 

post them tomorrow.  Tomorrow's version should be the final version.  

Note on names: per previous usage, XSD (Extensible or XML Structure 
Definitions) refers to 
the standard under construction. SDD (Structure Definition Document) refers to 

the schema/XMLDTD/etc. created using that standard.  (Better definitions are 
on the list of things to come very shortly.)  

Paul Prescod is using XSchema to describe this project, and slowly but surely 
my resistance to that title is declining.  I need to hear from people how they 
feel about that name - I don't mind using it, but I do want a consistent name 
for this project effective tomorrow.


1. SDDs shall use XML document syntax, using element nesting and attributes to 

describe all constraints that may be verified by a processor using XSD.

2. XSD shall define a transformation from SDDs to DTDs.

3. SDDs shall be capable of representing the normalized element and attribute 
structures defined in XML 1.0 DTDs.

4. SDDs shall be parseable, manageable, and manipulable using the same tools 
used to parse, manage, and manipulate XML documents.

5. SDDs shall be easy to create, read, and modify.

6. SDDs shall be easy to use in combination with a parser to provide 
structural validation of documents.

7. XSD shall include an SDD and an XML 1.0 DTD defining the structure of SDDs.

8. XSD shall suggest mechanisms for applying SDDs to documents.

9. XSD shall include mechanisms for extending the information included in 
SDDs to support metadata.

10. The XSD specification shall be readable,clear, and rigorous, using 
terminology and nomenclature as close to the XML 1.0 specification as 

11. The XSD specification will comply with and be consistent with W3C 
recommendations regarding XML.

12. SDDs shall provide constructs for human- and machine-readable 

13. XSDs shall support namespaces.

14. XSD shall provide authoring support.


Note that sequence doesn't matter; I'm putting new entries at the end to avoid 

numbering confusion, not to indicate precedence.  


13 - Namespaces, per Peter Murray-Rust.  This is an issue I've been grappling 
with all week. How to make best use of namespaces will be among the early 
questions in this project's development.

14 - Authoring, also per Peter.  Overlaps with 5 and 12 to some extent, but 
seems important.  Also moves us past 13 goals - we need all the luck we can 
get.  Or is 13 just a lucky baker's dozen?


9 - added "to support metadata".  Paul's description of possibly dangerous 
extensions is convincing.  I'm not sure "to support metadata" is enough, but 
I'm not sure how better to phrase it.  I think prescribing extension limits is 
something that will have to be done in the body of the document.


The XSchema/XSD question is the largest looming issue I see right now.


Please post comments, privately or publicly.  Tomorrow's draft will be the 
final version - no more large issues may be added.  

Also tomorrow, the steady flow of questions we need to resolve within this 
framework will begin.  I've built a set of questions; others are welcome to 
contribute.  To avoid overlapping questions, I'd appreciate it if people could 
send those to me privately. I'll collate them and post them (with attribution) 
as the process moves along.  Questions will begin fairly broad and move in to 
more tightly focused issues as development progresses.

This has been pretty amazing so far. I'd like to thank everyone who's 
contributed so far, and welcome everyone else to join in!  I think we've 
redefined the issues, creating a much more focused and much better project 
than I originally proposed, and that we have an excellent chance of making a 
very useful contribution to the XML community.

Simon St.Laurent
Dynamic HTML: A Primer / XML: A Primer / Cookies

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