From: Olivier D. <oli...@un...> - 2006-05-15 15:58:31
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Hello, Congrats for the 0.4 release! I was playing this morning with the nifty online queries and I am stuck with a common pattern requiring to "pipe" the queries. For instance, <ask format="ul">[[works_at::University]]</ask> retrieves the things that work at the resource University. This works well and retrieves Faculty. However, specially for querying wikis in which we find a lot of instances, one may be more interested in retrieving the things that work at an instance of University. I tried <ask format="ul">[[works_at::rdf:type::University]]</ask>, which does not work. Is this a supported but undocumented feature, or is this simply not supported yet? I started proposing some more and more complex queries exploiting the current content of the wiki on my user page [1]. If that makes sense to some of you, I will create a SemanticQueriesExample pages page showing typical queries and explaining why they work (or why they don't). Cheers, Olivier [1] http://wiki.ontoworld.org/index.php/User:OlivierDameron |
From: Denny V. <dv...@ai...> - 2006-05-16 13:42:27
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Hi Olivier, > However, specially for querying wikis in which we find > a lot of instances, one may be more interested in retrieving the > things that work at an instance of University. I tried > <ask format="ul">[[works_at::rdf:type::University]]</ask>, > which does not work. Is this a supported but undocumented feature, > or is this simply not supported yet? This is not supported. But the same thing can be asked like this: <ask format="ul">[[works at::<q>[[Category:University]]</q>]]</ask> This asks for everything that works at an instance of an University. > I started proposing some more and more complex queries exploiting > the current content of the wiki on my user page [1]. If that > makes sense to some of you, I will create a SemanticQueriesExample > pages page showing typical queries and explaining why they > work (or why they don't). Feel free to add such a page to [[Help:Inline queries]]. What I don't really like is the use of namespace'd relations from the RDF/RDFS/OWL standard. Semantic Mediawiki is aiming at a user who does not know much about Semantic Web stuff, and certainly does not know much about the OWL standard and such. So, I do not like the usage of rdf:type especially. And within the Ontoworld wiki I would like to see it established to use Categories instead of the is_a relation. But this is only my personal opinion :) I never thought about asking about subcategories of a category. Why should one want to do such a thing? I was a bit surprised by this queries. Just my two cents, denny |
From: Olivier D. <oli...@un...> - 2006-05-16 16:33:17
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Hi Denny, Thanks for the feedback On Tue, 16 May 2006 15:41:21 +0200, Denny Vrandecic <dv...@ai...> wrote: > > However, specially for querying wikis in which we find > > a lot of instances, one may be more interested in retrieving the > > things that work at an instance of University. I tried > > <ask format="ul">[[works_at::rdf:type::University]]</ask>, > > which does not work. Is this a supported but undocumented feature, > > or is this simply not supported yet? > > This is not supported. But the same thing can be asked like this: > <ask format="ul">[[works at::<q>[[Category:University]]</q>]]</ask> > This asks for everything that works at an instance of an University. I found out eventually :-) See for example queries 3 and 4 at, which is pretty close to your suggestion: http://wiki.ontoworld.org/index.php/User:OlivierDameron > What I don't really like is the use of namespace'd relations from the > RDF/RDFS/OWL standard. Semantic Mediawiki is aiming at a user who > does not know much about Semantic Web stuff, and certainly does not > know much about the OWL standard and such. I am not really convinced here: - I don't think we should settle for the lowest common denominator. Just because a little semantic description is still better than no semantic description at all (Jim Hendler said that a little semantics goes a long way) doesn't mean that we should stop here. For some concepts/classes such as Faculty or LeftThumb, it is possible to give a formal definition and that should not be overlooked (in my mind, at least). At best these definitions will be useful, at worse they will not be used. Why cripple intensionally the whole thing from the start? - Even if we provide some formal (potentially complex) definitions, they can still be completely ignored by users and applications - I think that importing ontologies into wiki for providing is a valuable approach. Semantic wikis can benefit from it because (1) they provide a common vocabulary for humans (2) it allows (semi)-automatic enrichment of the content of the wiki either by introducing new article or by enriching the mark-up within existing ones (3) it helps fill the gap between human and software consumption of resources. Conversely, I also hope that formal ontologies can benefit from semantic wikis as they provide a nifty base of instances (e.g. the article on Gustave Eiffel) and semi-formally defined classes (e.g. the ones about universities) > So, I do not like the usage of rdf:type especially. And within the > Ontoworld wiki I would like to see it established to use Categories > instead of the is_a relation. I think that this is pretty dangerous, as the use of categories is not semantically consistent among the articles of any wiki. Caterories are great exactly because they provide this level of fuzzyness: you use them to retrieve articles that match the topic more or less closely. For example, if you represent scientific articles within a wiki (just like for the SemWiki2006 conf) you can describe for each of them the categories it deals with (SemanticWiki, SemanticWeb, KnowledgeExtraction, Indexing...). Yet none of these articles are actual instances of these subjects, nor are they subclasses. Categories are for human consumption, and they provide the tool we need that formal definitions like subsumption or instanciation cannot perform. If we want to be more precise in our descriptions, we should use precise tools, and this is where rdf(s), owl and their friends come into the picture. By now I hope it is clear that I believe the two approaches to complete each-other. > I never thought about asking about subcategories of a category. Why > should one want to do such a thing? I was a bit surprised by this > queries. Well I believe this is both necessary and desirable because when yo udescribe things, you want to be as precise as possible (this is why we give the exact value of the superficy of countries), whereas when you want to retrieve things, we give more general criteria (e.g. the countries bigger than XYZ km2). In order to make the interpretation of these criteria automatic, we need semantics, this is what allows software the fill the difference of granularity. This is what will make your article (described with the category SemanticWiki) retrieved in a query on articles about the semantic web. Or am I completely mistaken ? It is great to have these discussions, I find it quite stimulating. Cheers, Olivier |
From: Markus <ma...@ai...> - 2006-05-16 14:17:41
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On Monday 15 May 2006 17:48, Olivier Dameron wrote: > Hello, > Congrats for the 0.4 release! > I was playing this morning with the nifty online queries and I am stuck > with a common pattern requiring to "pipe" the queries. > > For instance, <ask format=3D"ul">[[works_at::University]]</ask> retrie= ves > the things that work at the resource University. This works well and > retrieves Faculty. > > However, specially for querying wikis in which we find a lot of > instances, one may be more interested in retrieving the things that work = at > an instance of University. I tried <ask > format=3D"ul">[[works_at::rdf:type::University]]</ask>, which does not wo= rk. > Is this a supported but undocumented feature, or is this simply not > supported yet? It should work. A related remark first: if you want to say "rdf:type" then = you=20 might prefer to use MediaWiki's categories. For these, we already have some= =20 limited support for hierarchy data (so sub-category realtionsships are=20 respected). This is not the case for any user defined reltionship, be it=20 called "rdf:type" or not. So, instead of writing [[rdf:type::University]],= =20 consider using [[Category:University]]. In this way, you end up with two=20 individuals: an article University and a category (owl:class)=20 Category:University. This is not much of a problem for wiki usage, but of=20 course you cannot put the Category:University into other categories (you ju= st=20 can make it a subcategory). In short: you would use the owl-class model whe= re=20 classes are interpreted as sets of individuals -- not the rdfs class model= =20 where this is not the case. In any case, I would avoid calling relations rdf:... simply because this mi= ght=20 be misleading for the users. In the rdf export, every relation gets a URI=20 along the same scheme, no matter whether it starts with rdf: or not. So the= =20 real rdf:... properties are different from the wiki's relations. This said, here comes your query: <ask>[[works at::<q>[[Category:University]]</q></ask> or=20 <ask>[[works at::<q>[[rdf_type::University]]</q></ask> (it was necessary to use <q> instead of <ask> since MediaWiki's p=FCarser=20 callbacks cannot handle nested tags) I guess mutliple levels of nesting are not supported (or only to some degre= e).=20 Denny could give details. For more information on inline queries, see the=20 article http://wiki.ontowolrd.org/wiki/Help:Inline_queries. > > I started proposing some more and more complex queries exploiting the > current content of the wiki on my user page [1]. If that makes sense to > some of you, I will create a SemanticQueriesExample pages page showing > typical queries and explaining why they work (or why they don't). Sure, good idea! Remarks: * MediaWiki (Semantic or not) supports " " in article names. Hacks like "_"= or=20 CamelCase are no longer needed. Just write as in normal English texts.=20 * Feel free to put the examples at [[Help:Inline query examples]] and link = it=20 from [[Help:Inline queries]]. It would be a helpful addition to our=20 documentation. Best regards, Markus > > Cheers, > Olivier > > [1] http://wiki.ontoworld.org/index.php/User:OlivierDameron > > > ------------------------------------------------------- > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job > easier Download IBM WebSphere Application Server v.1.0.1 based on Apache > Geronimo > http://sel.as-us.falkag.net/sel?cmd=3Dlnk&kid=3D120709&bid=3D263057&dat= =3D121642 > _______________________________________________ > Semediawiki-user mailing list > Sem...@li... > https://lists.sourceforge.net/lists/listinfo/semediawiki-user =2D-=20 Markus Kr=F6tzsch Institute AIFB, University of Karlsruhe, D-76128 Karlsruhe ma...@ai... phone +49 (0)721 608 7362 www.aifb.uni-karlsruhe.de/WBS/ fax +49 (0)721 693 717 |
From: Olivier D. <oli...@un...> - 2006-05-16 16:50:11
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Hi Markus, On Tue, 16 May 2006 16:16:08 +0200, Markus Kr=F6tzsch <ma...@ai...> wrote: > > It should work. A related remark first: if you want to say "rdf:type" > then you might prefer to use MediaWiki's categories.=20 I really don't think so: how will I make the difference between [universiti= es or partos of universities] on one hand, and things that are somehow rela= ted to universities ont the other hand ? > For these, we > already have some limited support for hierarchy data (so sub-category > realtionsships are respected).=20 I think that the problem to solve should drive the choice of the tool, and = not the other way around. > This is not the case for any user > defined reltionship, be it called "rdf:type" or not. So, instead of > writing [[rdf:type::University]], consider using > [[Category:University]]. In this way, you end up with two > individuals: an article University and a category (owl:class) > Category:University. This is not much of a problem for wiki usage, > but of course you cannot put the Category:University into other > categories (you just can make it a subcategory). In short: you would > use the owl-class model where classes are interpreted as sets of > individuals -- not the rdfs class model where this is not the case. I am not sure I understand you correctly here: all owl:Class is an rdfs:Class. Even in owl, the subsumption relation is rd= fs:subClassOf and the instanciation relation is rdf:type. I agree that I shoud make University an owl:Class and not a rdf:Class > In any case, I would avoid calling relations rdf:... simply because > this might be misleading for the users.=20 then we probably need either a solution for hiding it from the user, or a s= olution for saying that the Is_a relation should be interpreted by formal t= ools as rdf:type. I am not so sure though. > In the rdf export, every > relation gets a URI along the same scheme, no matter whether it > starts with rdf: or not. So the real rdf:... properties are different > from the wiki's relations. Aaah, I was not aware of this. I find it confusing and somehow in contradiction with the capability to imp= ort ontologies. I can't think of any advantage for obfuscating the namespac= es like it is currently done. Any hint? > This said, here comes your query: >=20 > <ask>[[works at::<q>[[Category:University]]</q></ask> thanks > I guess mutliple levels of nesting are not supported (or only to some > degree).=20 Right. No big deal though, as I believe this kind of thing is exactly what = a reasoner (rdfs, DL,... whatever the user needs at usage time and accordin= g to its requirements) should do, and i don't see the point of having such = reasoners embedded within semediawiki. I started thinking about the possibi= lity to call externa lreasoning services, but nothing matured enough yet. > * MediaWiki (Semantic or not) supports " " in article names. Hacks > like "_" or CamelCase are no longer needed. Just write as in normal > English texts.=20 Point taken. This is an old habit from formal ontology tools and old school= wikis :-) > * Feel free to put the examples at [[Help:Inline query examples]] and > link it from [[Help:Inline queries]]. It would be a helpful addition > to our documentation. Will do. Cheers, Olivier |
From: Markus <ma...@ai...> - 2006-05-17 15:06:32
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On Tuesday 16 May 2006 18:50, Olivier Dameron wrote: > Hi Markus, > > On Tue, 16 May 2006 16:16:08 +0200, Markus Kr=F6tzsch > > <ma...@ai...> wrote: > > It should work. A related remark first: if you want to say "rdf:type" > > then you might prefer to use MediaWiki's categories. > > I really don't think so: how will I make the difference between > [universities or partos of universities] on one hand, and things that are > somehow related to universities ont the other hand ? I don't quite get this example, but I am sure that you can find many exampl= es=20 that demonstrate your point. We clearly do not increase expressivity by=20 limiting the set of URIs that wiki users can refer to! So this is all agree= d. Our motivation is in fact different. SMW is planned to be a tool for=20 semantically annotating a wiki in the wiki-way. The primary purpose here is= =20 to structure the existing data in the wiki. We want to give the users total= =20 freedom about the language elements, i.e. individuals, properties, classes,= =20 that are described or used for description. We do, however, not want to let= =20 users choose the structuring paradigm (e.g. "Do we use OWL or RDFS=20 classes?"). This should eventually be the choice of the wiki admin, since i= t=20 has many technical ramifications (which tools can you use? how complicated= =20 are certain tasks? ...). But if you allow reference to arbitrary URIs, then you might have users=20 referring to owl or rdf language constructs (which represent the underlying= =20 formalism) as if they were actual language elements (e.g. properties). This= =20 forces you to use either RDF or OWL-Full as a data model, and the admin has= =20 no choice. In other words, the use of external URIs is a feature by which a= =20 single article (and thus a single user) can enforce certain datamodels upon= =20 the whole wiki. We think that this creates problems for the typical semanti= c=20 web reuse scenarios, since you can no longer know what kind of data the wik= i=20 exports: one day it is OWL-DL, another day, it is OWL-Full with all=20 OWL-language constructs redefined, yet another day, you have nice polynomia= l=20 OWL-fragement of RDF. So everybody who uses the wiki's data must either=20 employ an OWL-Full reasoner ;-) or has to ignore/strip/reshape part of the= =20 RDF export and thus to effectively change the knowledge the wiki exports. T= he=20 wiki users cannot influence how this is done, and the reuser cannot foresee= =20 what language the wiki-users will decide on today. Other than this, I am fine with e.g. using some foaf-property like an=20 attribute within the wiki. And this might be enabled via=20 inter-project-link-like "interontology links" that are switched on or off b= y=20 the admin. Then the admin also might decide to enable "rdf:" if he likes th= is=20 concept of a wiki that can talk about the details of this W3C standard ... Best regards, Markus > > > For these, we > > already have some limited support for hierarchy data (so sub-category > > realtionsships are respected). > > I think that the problem to solve should drive the choice of the tool, and > not the other way around. > > > This is not the case for any user > > defined reltionship, be it called "rdf:type" or not. So, instead of > > writing [[rdf:type::University]], consider using > > [[Category:University]]. In this way, you end up with two > > individuals: an article University and a category (owl:class) > > Category:University. This is not much of a problem for wiki usage, > > but of course you cannot put the Category:University into other > > categories (you just can make it a subcategory). In short: you would > > use the owl-class model where classes are interpreted as sets of > > individuals -- not the rdfs class model where this is not the case. > > I am not sure I understand you correctly here: > all owl:Class is an rdfs:Class. Even in owl, the subsumption relation is > rdfs:subClassOf and the instanciation relation is rdf:type. > > I agree that I shoud make University an owl:Class and not a rdf:Class > > > In any case, I would avoid calling relations rdf:... simply because > > this might be misleading for the users. > > then we probably need either a solution for hiding it from the user, or a > solution for saying that the Is_a relation should be interpreted by formal > tools as rdf:type. I am not so sure though. > > > In the rdf export, every > > relation gets a URI along the same scheme, no matter whether it > > starts with rdf: or not. So the real rdf:... properties are different > > from the wiki's relations. > > Aaah, I was not aware of this. > I find it confusing and somehow in contradiction with the capability to > import ontologies. I can't think of any advantage for obfuscating the > namespaces like it is currently done. Any hint? > > > This said, here comes your query: > > > > <ask>[[works at::<q>[[Category:University]]</q></ask> > > thanks > > > I guess mutliple levels of nesting are not supported (or only to some > > degree). > > Right. No big deal though, as I believe this kind of thing is exactly what > a reasoner (rdfs, DL,... whatever the user needs at usage time and > according to its requirements) should do, and i don't see the point of > having such reasoners embedded within semediawiki. I started thinking abo= ut > the possibility to call externa lreasoning services, but nothing matured > enough yet. > > > * MediaWiki (Semantic or not) supports " " in article names. Hacks > > like "_" or CamelCase are no longer needed. Just write as in normal > > English texts. > > Point taken. This is an old habit from formal ontology tools and old scho= ol > wikis :-) > > > * Feel free to put the examples at [[Help:Inline query examples]] and > > link it from [[Help:Inline queries]]. It would be a helpful addition > > to our documentation. > > Will do. > > Cheers, > Olivier =2D-=20 Markus Kr=F6tzsch Institute AIFB, University of Karlsruhe, D-76128 Karlsruhe ma...@ai... phone +49 (0)721 608 7362 www.aifb.uni-karlsruhe.de/WBS/ fax +49 (0)721 693 717 |