It is now possible to store #ask queries on dedicated wiki pages. This has been suggested in order to shorten the URLs of RSS feeds and the like since these URLs currently must contain the whole query and RSS description. But storing queries has more advantages, including "query rights" management and potential for future caching (planned for SMW 1.3). This is also a big step in SMW's OWL and ontology modelling support (also to be extended in SMW 1.3).
== Details == It works as follows: SMW 1.2 has a new namespace Concept: and each page in that namespace can hold exactly one query. Imagine a concept to be like a "dynamic category": it always contains the set of pages that are described by the query. This is also a reason why we chose "Concept" instead of e.g. "Query". An example page is http://semanticweb.org/wiki/Concept:Semantic_Web_events_2008 The concept is described by a parser function #concept that provides a normal SMW query (first parameter) and an optional text description (second parameter). Example from the above page: {{#concept: [[Category:Event]] [[start date::> Jan 1 2008]] [[start date::< Dec 31 2008]] | Events in the year 2008 that have been announced on semanticweb.org. To add more events, go to the page "Events" on semanticweb.org. }} Concepts do not store further parameters that one may have in #ask (printouts, sorting conditions, format, etc.). They really just describe a set of things, like a category. This way, concepts can be used in queries just like categories. Here are some examples: {{#ask: [[Concept:Semantic web events 2008]] }} just shows the members of the concept {{#ask: [[Concept:Semantic web events 2008]] [[located in::Germany]] }} shows events that belong to the concept and are located in Germany {{#ask: [[Concept:Semantic Web events 2008]] | ?start date=start | ?end date=end | ?has location city=location | ?title=description | format=icalendar | limit=500 }} shows an iCalendar link to the 2008 events. The title and description of the exported calendar is taken from the concept in this case, so the URL does not have to contain all the description text. The last case works similar for RSS: if you use *only* a single concept for an RSS feed, and if you do not provide a description or title for the feed, then these values will be taken from the concept page (page title and concept description). This allows you to have much shorter feed URLs. Concepts also have the nice property that they make important queries in your wiki more explicit. In this way, SMW knows that a certain query is important to you and it can optimise answering of those queries (future work ;-). Also, SMW can *export* your queries now: click on the "RDF feed" link on a concept page to see the machine-readable version of the query. The OWL format that we use for export can nicely capture many SMW queries, and OWL tools can actually read these descriptions and reuse them externally. So SMW now cannot just export your wiki data, but also conceptual information about your topic. A practical tip: many wikis use templates for #ask queries, e.g. to use one query on many pages by making it refer to the current {{PAGENAME}}. Concepts in turn describe just one query, so one would need one concept per page. If you still want to make use of concepts in this case, you can make query templates that check if some Concept page exists (parserfuntion #ifexist), and use the direct #ask only if not. An example for this is Template:Yearly_calendar on semanticweb.org. It uses the above example concept for 2008, but it would insert a full #ask query for 2003 (where no concept page exists yet). In this way, we get shorter iCalendar URLs if possible, but still can use the template in cases where no Concept was created yet. A similar technique would work on sites with many RSS feeds. Finally, the fact that Concept is a separate namespace allows you to implement access control for queries. I will write a separate mail about this. Cheers, Markus -- Markus Krötzsch Semantic MediaWiki http://semantic-mediawiki.org http://korrekt.org [EMAIL PROTECTED]
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