• To: uzair ahmad <letsjoin@h...>
• Subject: Re: Can xsd ???
• From: Ronald Bourret <rpbourret@r...>
• Date: Mon, 18 Mar 2002 04:39:49 -0800
• Cc: xml-dev@l...
• References: <F224xPsXwlkwMis7hIY0001ceab@h...>

uzair ahmad wrote:

> Can a XML Schema Document perfectly describe some Database Schema. More
> specifivally , doese it have the enough vocabulary to decribe MetaData
> constarints (classes, attributes, relationships, datatypes ).

Describe, yes. Perfectly describe, no.

1) Tables can be described with elements with complex types.

2) Columns can be described with elements with simple types.

3) Nullability can be described by optionality of child elements.

4) Primary keys and primary key / foreign key relationships can (sort
of) be described by key/keyref. (I say "sort of" because key/keyref
applies to a single XML document. If your XML documents correspond to a
single row of data, key/keyref is insufficient for enforcing uniqueness
and referential integrity.)

5) The following cannot be described: cascading update/delete, triggers,
catalogs, schemas (in the catalog/schema/table sense), indexes, and all
of the database-specific things you find in CREATE TABLE statements.

-- Ron

• References:
  • Can xsd ???
    • From: "uzair ahmad" <letsjoin@h...>

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