Re: [SMW-devel] [patch] 2nd try: support for negated queries

[Markus <ma...@ai...>]

Hi Thomas,

thanks for the work (and good to hear the SpieleWiki runs on the new versio=
n)!=20
We agree and also would prefer the full negation patch. Our current roadmap=
=20
is to finish 1.0 first, which mainly hinges upon the inclusion (or=20
reimplementation) of the {{#ask}}-patch and some further fixes (service=20
links, Type:Boolean).=20

After that, we will go for new releases and new features. I would expect th=
at=20
your patch remains compatible for that time -- major changes of querying as=
=20
in 0.7->1.0 are not scheduled so soon. What might be revisited, however, is=
=20
the concrete syntax used for expressing negations. If I can manage to revie=
w=20
your patch before 1.0, then I will certainly add it right away -- the fact=
=20
that you successfully worked through our Storage API already impresses me=20
quite a lot :-) And, given that you are one of the few people who ever=20
actually read that code: we are also happy about any suggestions towards=20
improving the storage performance.


Btw another possibility to work-around your problem for now could be to fil=
ter=20
for the respective property values *on printout*. This is inefficient but O=
K=20
as long as the result set is not too large. To do this, one would use a=20
templated printout (format=3D"template" template=3D"...") and include an {{=
#if }}=20
into the template that checks the conditions to decide whether or not to=20
create any output. Note that one can also use format=3D"template" for print=
ing=20
tables by setting intro=3D"{|" and using a template that defines table-rows=
 in=20
wiki pipe syntax. It is also possible to use a template call for intro, so =
as=20
to get styling parameters set. Of course it's as ugly as any advanced=20
formatting in MediaWiki ...

Regards

Markus


On Dienstag, 20. November 2007, Thomas Bleher wrote:
> * Thomas Bleher <bl...@ci...> [2007-11-15 20:36]:
> > * Thomas Bleher <bl...@ci...> [2007-11-14 08:48]:
> > > 1) Implement negations in queries - then I could ask "(NOT
> > > maxTeilnehmer <=3D 9) AND (NOT minTeilnehmer >=3D 11)". I used this
> > > solution with SMW 0.7 (patch below), but looking at the 1.0RC2 code,
> > > I'm not quite sure how to implement it cleanly.
> >
> > I looked at the code again and tried to implement negation support. The
> > patch below adds a <n> </n> pair which negates the query in between. It
> > also adds a SMWNegation class (derived from SMWDescription), which
> > encapsulates the negation.
>
> OK, I took another stab at this, and in my limited tests the code works
> correctly now :)
>
> The code is online at http://pwiki.j-crew.de/wiki/Test, feel free to
> play around with it (it's just a test-wiki).
>
> Technical details:
> To work around the problems with INNER JOINs and negations, all INNER
> JOINs of the form "SELECT a INNER JOIN b ON a.c=3Db.d" are replaced by
> "SELECT a,b WHERE a.c=3Db.d". This may not be the most elegant solution,
> but the only workable I found.
>
> To make this work, addJoin now has an additional $where parameter.
>
> Beware: I still don't understand all the internals of query processing,
> so no guarantees for this code. I would really appreciate it if someone
> more knowledgeable than me would look over the code.
>
> Regards,
> Thomas



=2D-=20
Markus Kr=F6tzsch
Institut AIFB, Univers=E4t Karlsruhe (TH), 76128 Karlsruhe
phone +49 (0)721 608 7362        fax +49 (0)721 608 5998
ma...@ai...        www  http://korrekt.org