Re: [Xmldb-org-xapi] XPathQueryService

[Per N. <per...@re...>]

Hi Wolfgang,

Thanks for your reply. Please see my answers inline below:

tisdagen den 13 juli 2004 15.04 skrev Wolfgang Meier:
> Hi Per,
>
> > does anyone know why XPathQueryService.queryResource(String id, String
> > query) is returning a ResourceSet? Would it not make more sense to return
> > a XObject (org.xmldb.common.xml.queries.XObject) instead?
> >
> > i.e.change
> > ResourceSet queryResource( String id, String query ) throws
> > XMLDBException; to
> > XObject queryResource( String id, String query ) throws XMLDBException;
> >
> > We are querying a single resource and are not expecting a result from any
> > other resource and certainly not a set of resources.
>
> I agree that returning a ResourceSet is somewhat misleading. The query
> result could be anything: a set of atomic values, a node set or a document
> fragment. While storing a document fragment back into the database with
> Collection.storeResource is possible, storing an integer value doesn't make
> much sense.
>
> However, XObject seems too limited to me. First, because the name makes me
> expect a single object, second XObject restricts the possible range of data
> types. Why not use a more generic concept compatible with the XPath2/XQuery
> semantics? Every query returns a "Sequence" containing zero or more
> "Items". An item might be a node or an atomic value. JSR 225 chooses this
> path.

Yes but returning an array of XObjects is just this: a sequence of items that 
can contain atomic values, document fragments or nodesets.

As you know, an XObject is possible to get content as a
int, boolean, double string, NodeList and DocumentFragment. I think this 
covers all possibilities from an XPath result but we can easily add new ones 
if needed.

>
> > Returning an XObject makes it possible to handle xpaths that returns
> > numbers such as count() in a cleaner way than wrapping the result in XML
> > and turning it into a resource.
> >
> > Actually why not use the same logic for collection scope queries and
> > change it from:
> >
> > ResourceSet query( String query ) throws XMLDBException;
> > to
> > XObject[] query( String query ) throws XMLDBException;
> > ?
>
> I don't see why collection scope queries should have a different return
> type? query() and queryResource() just pre-set the context of the query,
> but this context can be changed at any time within the query expression,
> using the standard doc() and collection() functions. It is not possible to
> determine the result in advance.

I was thinking that if an XObject is a returned from a Resource than returning 
an array of XObjects from a a collection of Resources (one Xobject for each 
resource that has a match) would make sense.

Best regards,
Per

>
> Regards,
>
> Wolfgang
>
>
>
> -------------------------------------------------------
> This SF.Net email sponsored by Black Hat Briefings & Training.
> Attend Black Hat Briefings & Training, Las Vegas July 24-29 -
> digital self defense, top technical experts, no vendor pitches,
> unmatched networking opportunities. Visit www.blackhat.com
> _______________________________________________
> Xmldb-org-xapi mailing list
> Xml...@li...
> https://lists.sourceforge.net/lists/listinfo/xmldb-org-xapi