RE: Purpose of <xs:sequence/>

I've seen this happen a lot.  If a source has a very large data model and/or
schema, they may only want to communicate to a trading partner the data
nodes they need to care about.  Who wants to wade through a sometimes
gigantic schema when you only need to populate a minority of fields?

And so the data model removes unneeded data elements from the schema.  This
leaves empty sequence nodes.

Removing unneeded elements from a schema is a common request I have gotten
from clients.  It has caused me to create a real simple xslt based solution
which I call the "schema lightener".  It is explained here:
http://www.xmlhelpline.com/tools/index.html

FWIW,

Paul Kiel

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-----Original Message-----
From: xmlschema-dev-request@w3.org [mailto:xmlschema-dev-request@w3.org] On
Behalf Of Boris Kolpackov
Sent: Thursday, June 19, 2008 9:38 AM
To: Adam Retter
Cc: xmlschema-dev@w3.org
Subject: Re: Purpose of <xs:sequence/>


Hi Adam,

Adam Retter <Adam.Retter@landmarkinfo.co.uk> writes:

> <xs:complexType name="Classifier">
> 	<xs:sequence/>
> 	<xs:attribute name="pid" type="xs:string" use="required"/>
> </xs:complexType>

Having an empty sequence like this is valid and is equivalent to not
having one at all.

If the schema is auto-generated then it is easy to see why there
are empty sequence elements. The tool probably just adds the
sequence element (e.g., in DOM) and then iterates over elements
and adds them under it. In cases where there are no elements
you end up with an empty sequence. Someone may also want to do
this in a manually-created schema to highlight the fact that this
is a complex type with empty content (and not just a mistake).

Boris

-- 
Boris Kolpackov, Code Synthesis Tools   http://codesynthesis.com/~boris/blog
Open source XML data binding for C++:
http://codesynthesis.com/products/xsd
Mobile/embedded validating XML parsing:
http://codesynthesis.com/products/xsde