Re: Proposal: Searching XML

At 11:45 PM 4/20/2002 +0200, Sebastian Hammer wrote:
>[...] I would like to propose that the ZIG decides upon a
>convention for modelling the potential set of searchable
>access points (within an application domain or profile)
>using XPATH Path Expressions.

It might be useful to look at XPath in the context of XSLT.

As others have pointed out, a Z39.50 search really needs to
operate on an abstract model rather than a concrete model.
In effect, the concrete model is transformed to an abstract
model with access points, the search operation acts on the
transformed abstraction, and then records are retrieved
according to some other transformation (GRS-1, MARC, etc.).

If we view transformations as the key to Z39.50, then we
might see a role for XPath in the application of XSLT.
In other words, a query might specify in XSLT a certain
XPath expression to transform the concrete XML into an
abstract model with access points. This abstract model
can then be viewed as a flat structure that supports the
usual Z39.50 attributes. In a sense, this is just like
giving the Z39.50 system administrator access to XSLT as
a tool for setting up the association between Z39.50
attributes and the fields/operators of a given database
(sometimes known as a "semantic mapping" procedure).

On the retrieve side, an XSLT with XPath expressions is
simply applied to make records into whatever syntax is
desired. I suspect many Z39.50 implementors are already
supporting the use of externally-defined stylesheets.

Things get more interesting if an implementor wants to
allow an XSLT to be invoked a per query basis. From the
standards perspective, this piece might be viewed as
a query optimization problem rather than a query modeling
problem. (For instance, Dave's ZBig Server configuration
file can be created by a configuration wizard and that
wizard could be put in the hands of a searcher rather
than a system administrator.)

Eliot

Received on Monday, 22 April 2002 05:21:50 UTC