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Hi,

I'm relatively new to xml. I want to have a xml element of the form:

<!ELEMENT CAR (MAKE, COMPANY)>
<!ATTLIST CAR
TYPE PCDATA
PRICE PCADATA>

<!ELEMENT COMPANY (HQ, COMPANY_TYPE)>

Is there a way such that CAR/TYPE has the same value as
CAR/COMPANY/COMPANY_TYPE either using DTD or a schema . For example,
whenever,

CAR/COMPANY/COMPANY_TYPE = "PRICEY"
then,
CAR/TYPE = "PRICEY"

I think something like XPath is needed but am not sure how to go about
getting this. Can I use XPath inside XML elements to point to value of
other elements.

Vinay

wrote:
> Hi,
>
> I'm relatively new to xml. I want to have a xml element of the form:
>
> <!ELEMENT CAR (MAKE, COMPANY)>
> <!ATTLIST CAR
> TYPE PCDATA
> PRICE PCADATA>

PCDATA is for element character data content. For attributes just use
CDATA. You also need to specify if a value is compulsory (#REQUIRED)
or optional (#IMPLIED), eg

<!ATTLIST CAR TYPE CDATA #REQUIRED PRICE CDATA #IMPLIED>

> <!ELEMENT COMPANY (HQ, COMPANY_TYPE)>
>
> Is there a way such that CAR/TYPE has the same value as
> CAR/COMPANY/COMPANY_TYPE either using DTD or a schema. For example,
> whenever,
>
> CAR/COMPANY/COMPANY_TYPE = "PRICEY"
> then,
> CAR/TYPE = "PRICEY"

Not in an XML DTD. Something similar is possible in SGML (CONREF).
But why do you want to do this? It's only necessary to give information
once.

> I think something like XPath is needed but am not sure how to go about
> getting this. Can I use XPath inside XML elements to point to value of
> other elements.

No. That's something you do in your processing language (eg XSLT). But
using a Schema language may help.

///Peter
--
XML FAQ: http://xml.silmaril.ie/

W3C XML Schema identity constraints can enforce the kind of equality
you require -- see the W3C XML Schema Primer [1] for an introduction.

ht

[1] http://www.w3.org/TR/xmlschema-0/
--
Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
Half-time member of W3C Team
2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
Fax: (44) 131 650-4587, e-mail:
URL: http://www.ltg.ed.ac.uk/~ht/
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