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RE: Purpose of <xs:sequence/>

From: Adam Retter <Adam.Retter@landmarkinfo.co.uk>
Date: Thu, 19 Jun 2008 14:31:32 +0100
Message-ID: <E5AF08CA89940F45AE064CAFF25C8A900558194B@EXMXCLUSTER.corp.edrlandmark.net>
To: "Koray SAKIROGLU" <koray.sakiroglu@gmail.com>
Cc: <xmlschema-dev@w3.org>
Okay,

 

The reason this all came about is that I have been asked to load these
XML Schemas into Oracle 11g and Oracle doesn't like the <xs:sequence/>
elements at all.

 

I was wondering whether whilst it appears safe to remove them, if there
was a reason that they are there that I don't understand - perhaps some
XML Schema design subtlety that I don't understand?

 

So from your response, I assume removing them in actual fact makes no
difference? I wonder why XML Schema allows <xs:sequence/> and if this
isn't ambiguous?

 

Thanks Adam.

 

________________________________

From: Koray SAKIROGLU [mailto:koray.sakiroglu@gmail.com] 
Sent: 19 June 2008 14:15
To: Adam Retter
Subject: Re: Purpose of <xs:sequence/>

 

I looked at
http://www.sparxsystems.com/resources/xml_schema_generation.html and it
does indeed appear that those xml schema files were generated
automaticaly, it's probably the automatic behaviour of the schema
generator to add empty sequence declaration to complex type if they do
not already have xs:sequence content, you shouldn't let yourself get
bothered by those empty sequence declaration.

2008/6/19 Adam Retter <Adam.Retter@landmarkinfo.co.uk>:

 

It is in some XML Schemas that we have been given to work with from a
supplier. I believe that these were originally generated from a UML
modelling tool called Enterprise Architect.

 

 

Thanks Adam.

 

________________________________

From: Koray SAKIROGLU [mailto:koray.sakiroglu@gmail.com] 
Sent: 19 June 2008 13:53
To: Adam Retter
Subject: Re: Purpose of <xs:sequence/>

 

Where did you see such declaration of <xs:sequence/> ?

Was it in a xsd file editor-generated from a xml file ? 

2008/6/19 Adam Retter <Adam.Retter@landmarkinfo.co.uk>:


Hi Chaps,

I am having trouble understanding what the purpose of an empty sequence
declaration is?

e.g. - <xs:sequence/> or <xsd:sequence/>

Certainly it seems to have no relevance in a document instance of that
Schema.

For example in one of the Schemas here we have global declarations like
this -

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


In this case it's probably to avoid possible error if someone were to
complete the schema and add the sequence [b]after[/b] the attribute
(call it declaration etiquette).
 

	
	<xs:element name="Reference" type="Reference"/>
	<xs:complexType name="Reference">
	       <xs:sequence/>
	</xs:complexType>


No idea, this is basicaly a tag without content or attribute, it could
as well have been a simple element, maybe the creator is planning to
complete his element later on and decided to make it complex ?

All in all, I see no real point to such declaration, much could depend
on where you saw such declaration, maybe an erroned/out of date editor?
 

	
	
	There is probably some design subtlety that I am missing, can
someone
	explain it?
	
	Thanks
	
	Adam Retter
	
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Received on Thursday, 19 June 2008 13:32:44 UTC

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