- From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
- Date: 22 Feb 2001 11:20:14 +0000
- To: Eddie Robertsson <eddie@allette.com.au>
- Cc: Faroukh Fekravar <fekravar@austin.apc.slb.com>, xmlschema-dev@w3.org
Eddie Robertsson <eddie@allette.com.au> writes:
> "Henry S. Thompson" wrote:
>
> > > 2) I understand that the Identity-constraint is valid within a defined
> > > scope. Is there anyway to
> > > define the key in the example above within the "Item1" element but
> > > declare somehow that
> > > the scope is the whole document (something like this:)
> > >
> > > <element name="Item1" type="Item1Type" >
> > > <key name="Item1Key">
> > > <selector xpath="Schema/Project/Item"/>
> > > <field xpath="@Id"/>
> > > </key>
> > > </element>
> > >
> > > <xsd:element name="Project">
> > > <xsd:complexType>
> > > <xsd:sequence>
> > > <xsd:element ref="Item1" maxOccurs="unbounded"/>
> > > </xsd:sequence>
> > > </xsd:complexType>
> > > </xsd:element>
> >
> > Sure, just put the key in whatever element declaration covers the
> > document element, and change the selector to
^^^^^^^^^^^^^^^^
> > <selector xpath=".//Item"/>
>
> I'm a bit confused here. I thought that the declaration of the key
> needed to be declared in the element that defines the scope of the
> uniqueness. Isn't this the case?
Yes -- I've underlined above the fact that I'm suggesting making the
whole document the scope for the key you're interested in.
> For example:
>
> If I have an instance like:
>
> <Root>
> <Item id="1">...</Item>
> <Item id="2">...</Item>
> <Item id="3">...</Item>
> </Root>
>
> If I want Item/@id to be unique within the scope of the Root element
> I thought the key declaration had to come in the element declaration
> of the Root element:
>
> <xsd:element name="Root" type="RootType">
> <xsd:key name="ItemKey">
> <xsd:selector xpath="Item"/>
> <xsd:field xpath="@Id"/>
> </xsd:key>
> </xsd:element>
Correct -- that's what I said above.
> Is it really true that you can define the key within the Item element itself?
> Like:
>
> <xsd:element name="Item" type="ItemType">
> <xsd:key name="ItemKey">
> <xsd:selector xpath=".//Item"/>
> <xsd:field xpath="@Id"/>
> </xsd:key>
> </xsd:element>
>
> Are these two declarations equal and if they are how is the scope of the
> uniqueness defined?
No, not equal, and the second as you suggest pretty useless. Sorry
for the confusion, please try reading my original reply again.
ht
--
Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
W3C Fellow 1999--2001, part-time member of W3C Team
2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
URL: http://www.ltg.ed.ac.uk/~ht/
Received on Thursday, 22 February 2001 06:20:21 UTC