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pcplantdb - Re: [pcplantdb] Formal Spec

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  • From: Richard Morris <webmaster@pfaf.org>
  • To: Permaculture Plant Database <pcplantdb@lists.ibiblio.org>
  • Subject: Re: [pcplantdb] Formal Spec
  • Date: Thu, 10 Feb 2005 17:52:28 +0000

Lawrence F. London, Jr. wrote:
John Schinnerer wrote:

IMO an XML DTD will be a part of formal specs - specifically, it will be the spec for XML markup to be used however we end up using XML markup in the project.


What is a DTD
And what is a schema (scheme, simply put?)


A DTD stands for Document Type Definition (or something like that)
they are used to specify whats allowed in an XML document and specify how it should be structured.

For example a DTD for HTML would list the allowed tags <p>, <b>, <h1> etc and where they could appear.

An XML Schema does a similar job, but has a slightly different emphesis.
Advantages are
* XML Schemas are extensible to future additions
* XML Schemas are richer and more useful than DTDs
* XML Schemas are written in XML
* XML Schemas support data types
* XML Schemas support namespaces
(stolen from http://www.w3schools.com/schema/schema_intro.asp)

You also get Schema for databases which describe the structure of a database, i.e. the tables and fields in the tables.

Rich





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