[xsd-users] XSD and XPath

[Attila]

Thanks Boris,

On Fri, May 9, 2008 at 8:17 AM, Boris Kolpackov <boris at codesynthesis.com>
wrote:

> Hi Attila,
>
> Attila <atteeela at gmail.com> writes:
>
> > I am wondering if it is possible to use XPath expressions against an XSD
> > object model to obtain a particular node.
> > I know that I could do XPath queries against an instance document and
> then
> > convert to object model, but that is too expensive.
>
> XPath can be used together with the DOM document association feature.
> This feature allows you to maintain bidirectional association with
> DOM and object model nodes. You can then execute XPath queries on
> the underlying DOM document, obtain resulting DOM node(s), resolve
> associated object model nodes and handle the result using the more
> convenient object model. In fact, in the next release of XSD we will
> include an example on how to to this. For the current release you
> can download this example via this link:
>
> http://codesynthesis.com/~boris/tmp/xpath.tar.gz<http://codesynthesis.com/%7Eboris/tmp/xpath.tar.gz>
>
> Note also that the above approach has a number of limitations: the
> DOM association is created only when you parse an XML document to
> the object model and underlying DOM nodes do not automatically
> reflect changes made to the object model and vice versa. For more
> information on DOM association see Section 5.1, "DOM Association"
> in the C++/Tree Mapping User Manual:
>
> http://codesynthesis.com/projects/xsd/documentation/cxx/tree/manual/#5.1
>
>
> > Another question is:  Will the object model be populated with the
> defaults
> > specified in the schema if the elements/attributes are not present in an
> > instance document?
>
> If XML Schema validation is enabled in Xerces-C++ then default values for
> both attributes and elements are automatically assigned in DOM and in the
> object model.
>
> If XML Schema validation is disabled then the generated code assigns
> default values for attributes (elements with default values are quite
> inconvenient and therefore are not widely used, I don't remember ever
> seeing a practical schema using them). Note also that there will be no
> default attributes or elements in DOM with this setup.
>
> Boris
>



-- 
Attila
Software Developer
atteeela at gmail.com