On Wed, Apr 23, 2008 at 2:23 AM, Markus Krötzsch <mak@aifb.uni-karlsruhe.de> wrote:
On Dienstag, 22. April 2008, Sergey Chernyshev wrote:
> Markus,
> It's great news and I'll definitely be looking into RAP implementation for
> integration with other tools we use!
> I have a couple of questions regarding the iCal and SMWRegistry though:
>    - Why do you use this strange encoding for the queries and other
>    things in RSS/iCal URLs? it seems that you replace % with - which makes
> it harder to interpret or create. I wonder what's the reasoning behind
> this, why can't you just use regular url encoding?

There are multiple reasons. The main reason is that we want to create internal
links in MediaWiki to the query special page. Now if we would use % encoding,
then MediaWiki would expand that in links to create symbols that are not
allowed in links. You can try the query link:


(query "[[Category:Testpage]]")

Another reason is that we use this as a common encoding in all contexts that
occur in SMW. Now in RDF/OWL, URLs do alse occur as XML entities, and % is
not allowed in such entities either.

I see. Maybe there should be some easy way to create RSS links - I use them with FeedBurner (a fixed set of links, which does not allow dynamic feeds by topic, for example) and they were pain in the neck to create, also I had to hide all the complexity behind mode_rewrite rule (actually Apache freaked out on this URLs too so I did it on my reverse proxy I use) because FeedBurner failed to understand these long URLs.

It brings the question of savable queries - I wrote about this idea in context of performance if you remember. In two words, it might make sense to create special namespace for saved queries - where each page will define a query and then that page serves as a name shortcut that can be used instead of the full syntax. I use this approach in my Widgets extension: http://www.mediawiki.org/wiki/Extension:Widgets - SMW can use it in various places, e.g. as argument to {{#ask}} (instead of full query), as arguments to RSS/iCal and other exporters and so on. This will relief developers from URL issues (and also as I mentioned in last post, might be usable for restricting querying functionality if combined with namespace permissions).

Let me know what you think - I'll be happy to discuss in more detail if needed.

>    - SMW Registration is done by parsing Special:Version as I understand
>    - why not to create an RDF export of the statistical data that your
> service can consume in addition to the base data in Special:Version? I
> understand that old version will not contain it, but there are lots of
> other useful data that can be extracted and why not to use best Semantic
> format to do that? The project is called "Semantic" MediaWiki, right? ;)

We do :-) But that feature is only available since 1.1, hence we check
Special:Version to be able to register also older SMWs. But all the
additional information (e.g. page count) comes from Special:ExportRDF?stats.
It would otherwise be very hard to parse this data from Special:Statistics in
all languages.

Perfect! Now everyone can create a tool for visualizing SMW statistics.

BTW, how do I get http://semantic-mediawiki.org/wiki/Special:SMWRegistry page as RDF? with seeAlso links to specific feeds for each wiki?

> I'll definitely try to upgrade TechPresentations, although first I'll need
> to make sure that the rest of SMW extensions work fine.

OK, great. I think the leap from 1.0 to 1.1 is not so large regarding internal
stuff, so I am confident that no issues with extensions arise.
TechPresentations of course cannot be registered anyway, since it blocks
robots (btw, the SMW Registry robot should understand the ALLOW clause in
robots.txt ;-)

I actually added it to robots.txt and will probably allow Special:ExportRDF universally.
I will soon (today) create another minor release since we spotted some
problems with the 1.1 ICalendar export on various systems, which we fixed
right away.

OK, I didn't upgrade to latest SMW yet, but I definitely plan it for near future. Is there any way to roll-back SVN easily? I know you use WikiMedia's wiki and they don't encourage tags or branches, but it might be very useful to be able to roll-back somehow. Maybe it's worth posting a timestamp for each release so it can be used for checkout?


Sergey Chernyshev



Markus Krötzsch
Institut AIFB, Universität Karlsruhe (TH), 76128 Karlsruhe
phone +49 (0)721 608 7362          fax +49 (0)721 608 5998
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