On Sat, Feb 20, 2016 at 12:24 AM, Hans-Juergen Rennau <hrennau@yahoo.de> wrote:
> Dear BaseX team,
>
> perhaps I hear an opinion about the following idea.
>
> (1) The function xquery:parse is already immensely useful as it allows to
> *validate* XPath expressions, as for example used in configuration data. (A
> practical example: the XPath expressions used in JMeter [1] test plans in
> order to extract message data and define test assertions.)
>
> (2) Given the XSDs of a Web Service (or other application), it is possible
> to determine all valid data paths (e.g. /a/b/c is valid, /a/b/C is not
> valid).
>
> (3) If there were a reliable way to map the output of xquery:parse to the
> implied data paths, then one could use xquery:parse to validate xpath
> expression not only for syntactic correctness (which is already very much!),
> but also for consistency with application XSDs. This would be extremly
> usefuly as XSDs evolve and a checking if configuration-based XPath
> expressions must be adapted is otherwise very difficult to achieve in any
> systematic way.
>
> (4) Looking at the xquery:parse output, it seems certainly feasible to write
> such a mapping (xquery:parse output => data paths); but the problem I see is
> that the format is not guaranteed to be stable, as it is no standard. (And
> it is probably not described.) If BaseX provided such a functionality as an
> additional extension function (e.g. xquery:data-paths($query as xs:string))
> you would simply be - heros.
>
> Cheers,
> Hans-Jürgen
>
> [1] http://jmeter.apache.org/
>
> PS: Illustrative example.
>
> let $query := "/descendant::OutboundFlight[Status =
> 'Booked'][1]/FlightDeparture/DepartureTime"
> return xquery:parse($query)
> =>
> <MainModule updating="false">
>  <QueryPlan compiled="false">
>    <CachedPath>
>      <Root/>
>      <IterPosStep axis="descendant" test="OutboundFlight">
>        <CmpG op="=">
>          <CachedPath>
>            <IterStep axis="child" test="Status"/>
>          </CachedPath>
>          <Str value="Booked" type="xs:string"/>
>        </CmpG>
>        <Int value="1" type="xs:integer"/>
>      </IterPosStep>
>      <IterStep axis="child" test="FlightDeparture"/>
>      <IterStep axis="child" test="DepartureTime"/>
>    </CachedPath>
>  </QueryPlan>
> </MainModule>
>
> let $query :=
> "/descendant::OutboundFlight[FlightDeparture/DepartureDate][1]/FlightDeparture/DepartureDate"
> return xquery:data-paths($query)
> =>
> //OutboundFlight/FlightDeparture/DepartureTime,
> //OutboundFlight/Status
>