Research Blog of Alexander Sigel

Topic Maps and RDF scutters (assertion spidering bots): State of the art?

2006-02-16T02:03:00.000-08:00

I am looking for the state of the art in Topic Maps and RDF scutters (assertion spidering bots).
Do you have any useful pointers/hints?

The growing use of semantic knowledge technologies like RDF and Topic Maps should result in larger collections of represented assertions available on the internet. Scutters (information agents spidering such assertions) could collect and integrate them.

One example of such an assertion scutter is:
http://rdfweb.org/topic/Scutter
http://rdfweb.org/topic/ScutterVocab

I have sketched the idea in my blog entry dated 24th Nov., 2005.
http://asigel.blogspot.com/2005/11/ideas-for-aggregation-of-distributed.html

Do you have any information concerning the following four questions:

(1)
Which available collections of statements/assertions do you know and can you recommend to me for an aggregation scenario?

I want to use them in a content aggregation scenario where statements about the same subjects are collocated. Ideally, such a collection would use Published Subjects (or subject indicators). I am particularly looking for topic map data, but would also like to know about RDF data, since accorcing to the latest guidelines in semantic interoperability, useful mappings are possible between Topic Maps and RDF.

MusicBrainz is one example for a semantic web service with RDF.
There are also e.g. approaches for converting genealogical data (GEDCOM) to RDF FOAF,
or one might use DMOZ RDF data.

(2)
Which scutters (spidering information agents for RDF and/or topic maps
(or fragments) do you know/can you recommend?

I am planning to use:
http://search.cpan.org/~kjetilk/RDF-Scutter/
a LWP agent based on RDF::Redland.

Does something similar already exist for Topic Maps?

I know of some Java agents,
in particular the CC-licenced
Slug: A Simple Semantic Web Crawler (December 09, 2004) http://www.ldodds.com/blog/archives/000167.html
http://aloo.gnomehack.com/~ldodds/projects/slug/javadoc/

SECO contains an
RDF Crawler: Scutter (Bash and Pyhton for Scuttering) http://triple.semanticweb.org/svn/aharth/2004/wwwnyc/seco-talk.html
http://www.harth.org/andreas/2004/ieeeis/
SECO: mediation services for semantic Web data Harth A IEEE Intelligent Systems, (USA) May/Jun 2004, Vol 19 No 3, 66ff.
Harth and Gassert describe a 103 MB test data set they compiled:
On Searching and Displaying RDF Data from the Web http://sw.deri.org/2004/12/derisearch/Eswc2005Demo.pdf

In addition, researchers in SNA (Social Network Analysis) write scutters.
The data set compiled e.g. by PhD student Peter Mika is impressive:
Social Networks and the Semantic Web
http://doi.ieeecomputersociety.org/10.1109/WI.2004.10039

There exists a Redfoot-RDF-Scutter in Python:
http://redfoot.net/scutter/
for which a REST interface has been proposed:
Sun, 29 Jan 2006
A RESTful Scutter Protocol for Redfoot Kernel http://copia.ogbuji.net/blog/2006-01-29/A_RESTful_

There is a Javascript extension for Mozilla:
Scuttering Composite RDF Datasource
http://nachbaur.com/software/mozilla/objects/index.xhtml

In his research proposal "Mining the Semantic Web", Ajay Chakravarthy in section 2.4 names some existing tools http://www.dcs.shef.ac.uk/~ajay/reports/Research%20Proposal.pdf
(Ontotext, Hackdiary, others with poor performance)
HyperSpider - HyperSpider (Java app) collects the link structure of a website. Data import/export from/to database and CSV-files. Export to Graphviz DOT, Resource Description Framework (RDF/DC), XML Topic Maps (XTM), Prolog, HTML. Visualization as hierarchy and map.
http://hyperspider.sourceforge.net/
(I could export website interlinkings with this, but this is formal metadata)

A List of RDF Crawlers
http://www.dbis.informatik.uni-frankfurt.de/~tolle/RDF/RDFReferences.html
(4 entries)
* RDF Crawler (in Java) from Institute AIFB, University of Karlsruhe, Germany
* Decentralised and reliable resource discovery using RDF metadata (also known as Fydra)
* DAML Crawler
* RDF Crawling Services - RDF Gateway
LuMriX which is topic map-based contains a crawler, but I know not enough about it.
http://www.lumrix.de/xmlsearch_keyfacts.php

(3)
Which sites freely offer semantic web services?
I want to retrieve assertions, i.e. fragments of knowledge networks realized with Topic Maps or RDF.
Preferably with a possibility to retrieve by published subject (or subject indicator).
Indirect search by name where I assert the identity of the subject might do for the moment.

(4)
Do you know of demo sites which can be externally queried with TMRAP 0.2 (or higher: 1.0, 2.0)?

Scratchpad of additional references:
(not yet checked)
------------------------------------

Current State of Semantic Web Mining
http://www.fernuni-hagen.de/DVT/Aktuelles/zhao_yi.pdf
Check starting slide 38, but not so useful for this purpose
Ontobroker, which includes
an ontology-based web-crawler

DefineCrawler
http://www.lalic.paris4.sorbonne.fr/stic/octobre/octobre/apr/Nauer.pdf

RDFWeb notebook: aggregation strategies
http://rdfweb.org/2001/01/design/smush.html
(describing Swoogle)

Finding and Ranking Knowledge on the Semantic Web http://www.cs.umbc.edu/~ypeng/Publications/2005/iswcLiDing.pdf

Search on the Semantic Web
http://www.cs.umbc.edu/~ypeng/Publications/2005/IeeeSemanticWebSearch.pdf

JNotes. Automatic Generation of Semantic Networks
http://www.jnotes.de/JNotes/jnotes_webware.nsf/0/2DC6FB39AE566557C12570EC00307C3B?openDocument

[xtm-wg] Sketch of a Possible Algorithm for Fragment Grabbing (2000) http://lists.oasis-open.org/archives/topicmaps-comment/200007/msg00018.html

Pragmatic applications of the Semantic Web using SemTalk.
The agents are supported by crawlers searching proactively or after request for existing models to generate index files for the agents. The crawlers do not only look in the local filesystem, but also in the Semantic Web, for available knowledge sources in the RDFS format.
http://www.semtalk.com/pub/KnowTech2001.htm

Metadata-based Web Querying
http://www.cs.bilkent.edu.tr/~ismaila/research_projects.htm

RDFStore
Perl/C RDF storage and API
http://rdfstore.sourceforge.net/

CARA is an RDF API written in Perl
http://cara.sourceforge.net/

---

TMRA 2006: International Conference on Topic Maps Research and Applications, Leipzig (DE)

2006-02-16T01:25:00.000-08:00

TMRA 2006 - International Conference on Topic Maps Research and Applications"
Leveraging the Semantics"
Leipzig, Germany, 11-12 October 2006
http://www.informatik.uni-leipzig.de/~tmra/2006/

Full disclosure: I am co-chair of the program committee

Ideas for the aggregation of distributed (P2P) RDF and Topic Maps

2005-11-24T08:10:00.000-08:00

This blog entry is about some ideas on how to aggregate content with markup in RDF and topic maps which is distributed over the web. The aggregation may also be accomplished P2P-like.

1. Problem space/application areas
-----------------------------------
I want to use existing RDF/Topic Maps annotations. Those can be understood as disaggregations of underlying texts, dervice by humans annotating.

My aggregation will lead to innovative knowledge products and knowledge services.

I will not only aggregate assertions, but also aggregate (compose) knowledge services. A knowledge service can be implemented with TMRAP on top of a topic map.

See e.g. the slides of my talk
kPeer (Knowledge Peers): Informationssuche beim verteilten SemBloggen

The project "SemNetMan" (Semantisch basiertes Netzwerkmanagement) [1] combines:
SNA (Social Network Analysis) with Semantic Web Technologies

Similarly, Peter Mika is doing his dissertation research [2] on Social Networks and the Semantic Web, applying it to Flink [3].

I myself want to achieve semblogging, integration of content from weblogs which have semantic markup.

2. Architecture
---------------
According to [4], three elements are useful for this:
(1) RTM (RDF to topic maps mapping),
(2) PSIs, and
(3) topic map content distributed on the web

RTM is currently implemented in the commercial solution OKS and the Omnigator, and according to the slides, a TMAPI implementation is also under way (but I do not know the status and which backend would support that already).

A tutorial-like description for RTM mapping (for SKOS) is given in [5], and a description of RTM itself can be found in [6, 7].

So, where do I get a PSI collection from?

TopicMapster (TMShare) [8] is the idea of exchanging topic map fragments in P2P fashion.

This has meanwhile become possible in practice with TMRAP (Topic Maps Remote Access Protocol) [9] (version 1.0 will be available end of 2005 in OKS)
It is a web service for Topic Maps
For an explanation, see [10, 11]

Which (free) topic map software does/will support TMRAP?
(There seems to be some early TMRAP support in TM4J? (see Sourceforge-CVS of TM4Web)

Alternative approaches:
TMIP [12], or SNAPI [13]

3. Technical tools
-----------------
To collect RDF triples from various sources into one store, one could use, on an experimental basis, RDF::Scutter [14]. It is a web robot collecting distributed RDF into a central store.

It is based on RDF::Redland [15], a Perl binding for Redland framework [16]. Redland itself is a "free, open source C library for parsing, storing and querying RDF files"

(Yes, there is also a Java binding for Redland) [17]

Redland is useing RDQL for queries [18]

Two tutorials how to use RDF::Redland from Perl [19, 20]

To bind RDF triples to Perl objects in general, one can use Class::RDF [21]

References
[1]
http://www.semantics2005.net/semnetman-semantisch-basiertes-management-sozialer-netzwerke.workshop.60.11.htm

[2]
http://www.cs.vu.nl/~pmika/research.html
http://www.cs.vu.nl/~pmika/research/papers/VUBIS-PhDproposal.doc

[3]
http://flink.semanticweb.org/

[4]
[Garshol & Naito 2004] Realization of seamless knowledge: connecting distributed RDF and Topic Maps", presented 2004-11-06 at SIG-SWO-A403-04
http://www.jaist.ac.jp/ks/labs/kbs-lab/sig-swo/papers/SIG-SWO-A403/SIG-SWO-A403-04.pdf (2 pages, Abstract)
http://www.knowledge-synergy.com/topicmaps/document/sig-swo.pdf (16 slides, PDF)

[5]
Garshol, Marius: SKOS in Topic Maps
Blog entry 2005-10-24
http://www.garshol.priv.no/blog/10.html

[6]
The RTM RDF to topic maps mapping: Definition and introduction
2003-12-28
http://www.ontopia.net/topicmaps/materials/rdf2tm.html

[7]
Lars Marius Garshol: Living with topic maps and RDF: Topic maps, RDF, DAML, OIL, OWL, TMCL
http://www.ontopia.net/topicmaps/materials/tmrdf.html

[8]
Ahmed, Khalil (2003): TMShare - Topic Map Fragment Exchange In a Peer-To-Peer Application. In: Procs. XML Europe 2003, 2003. http://www.idealliance.org/papers/dx_xmle03/papers/02-03-03/02-03-03.html
http://www.techquila.com/topicmapster.html

[9]
Pepper, Steve (2004-04-17): Topic Maps Remote Access Protocol 0.2
(Technical report)
http://www.jtc1sc34.org/repository/0507.htm

[10]
[Garshol 2006] Garshol, Lars Marius (2006): TMRAP: A Web Service Protocol for Topic Maps. Procs. TMRA'05, International Workshop on Topic Map Research and Applications, Leipzig, Oct 6-7, 2005. Springer (under preparation)
Online: http://www.informatik.uni-leipzig.de/~tmra05/PRES/LMGa.pdf (slides)

[11]
[Pepper & Garshol 2004] Pepper, Steve & Garshol, Lars Marius (2004): Seamless Knowledge. Spontaneous Knowledge Federation using Topic Maps. Late breaking talk, presented at Extreme Markup Languages 2004, Montréal, Quebec, Canada, August 2-6.
Online:
http://www.ontopia.net/topicmaps/materials/Seamless%20Knowledge%20with%20TMRAP.ppt
(slides, with title: Seamless Knowledge. Spontaneous Knowledge Federation using TMRAP)

[12]
Barta, Robert: TMIP, a RESTful Topic Maps Interaction Protocol,
Presentation at Extreme Markup 2005
http://www.mulberrytech.com/Extreme/Proceedings/xslfo-pdf/2005/Barta01/EML2005Barta01.pdf

[13]
SNAPI - Semantic Network API
http://sourceforge.net/projects/snapi

[14]
RDF::Scutter
http://search.cpan.org/~kjetilk/RDF-Scutter-0.1/lib/RDF/Scutter.pm

[15]
RDF::Redland
http://search.cpan.org/~djbeckett/Redland-0.9.14.1/

[16]
Redland
http://librdf.org/

[17]
Java-Binding for Redland
http://librdf.org/docs/java.html

[18]
RDQL
http://www.w3.org/Submission/RDQL/

[19]
http://www.robertprice.co.uk/robblog/archive/2004/10/Querying_RDF_In_Perl_with_RDF_Redland.shtml

[20]
Barta, Robert (Perl expert in the topic maps community)
http://james.bond.edu.au/courses/inft73371/043/redland.mc

[21]
Class::RDF
http://search.cpan.org/~zooleika/Class-RDF-0.20/

SnipSnap (Weblog and Wiki) and K-Logs

2005-10-18T01:37:00.000-07:00

While checking SnipSnap, the free "easy Weblog and Wiki Software", I encountered the concept of K-Logs (knowledge management weblogs, in short: klogs), and hence klogging. Cool!
http://www.snipsnap.org/space/k-logs.

In consequence, this might lead us to "semklogging" instead of semblogging, of course :-)

2005-10-17T05:20:00.000-07:00

Sent Lutz Maicher some comments on his German Terminology of TMDM Topic Map terms

http://www.informatik.uni-leipzig.de/~maicher/tmt/latest_tmt.pdf

I should probably one day check the finalized version against my thesis.

Semantic Wikis (SemWikis), Topic Map Wikis and Semblogging

2005-10-14T07:19:00.000-07:00

How can I couple (Topic Map-based) semblogging with SemWikis?

Would one write LTM on the wiki pages and/or use a topic map editor?

Karsten Böhm (boehm@informatik.uni-leipzig.de) kindly pointed me to some references in SemWiki land at University of Leipzig, Germany:

David Aumüller (http://dbs.uni-leipzig.de/~david/) in the database department works on semantic wikis (http://wiki.navigable.info). With his project called WISAR (Semantic Authoring and Retrieval within a Wiki), wisar.sourceforge.net, he won the ESWC2005 Best Demo Award! Alternative name: WikSAR Wiki.
Sören Auer (http://www.informatik.uni-leipzig.de/~auer/) in the computer science department works also on semantic wikis (no publications yet). The group will start a joint project where SemWiki techniques will be employed to support software development process (requirements engineering). He will do a seminar on SemWikis (https://wiki.imise.uni-leipzig.de/SoerenAuer/SemSemanticWiki?v=9u9)

In addition I found:

SemWiki (http://ontoware.org/projects/semwiki/). SemWiki is a true RDF wiki. All wiki content is stored and processed as RDF.
There was a seminar on semweb technologies, including a seminar paper on SemWikis (http://www.aifb.uni-karlsruhe.de/Lehre/Sommer2005/SemTech/).
References
[1]
Stefano Emilio Campanini, Paolo Castagna, and Roberto Tazzoli. Platypus wiki: a semantic wiki wiki web. In Semantic Web Applications and Perspectives, Proceedings of 1st Italian Semantic Web Workshop, DEC 2004.
@INPROCEEDINGS{campanini04,
AUTHOR = {Stefano Emilio Campanini and Paolo Castagna and Roberto Tazzoli},
TITLE = {Platypus Wiki: a Semantic Wiki Wiki Web},
BOOKTITLE = {Semantic Web Applications and Perspectives, Proceedings of 1st Italian Semantic
Web Workshop},
YEAR = {2004},
MONTH = {DEC},
URL = {http://semanticweb.deit.univpm.it/swap2004/cameraready/castagna.pdf}
}
[2]
Adam Souzis. Rhizome position paper. In Proceedings of the 1st Workshop on Friend of a Friend, Social Networking and the Semantic Web, SEPT 2004.
@INPROCEEDINGS{rhizome05,
AUTHOR = {Adam Souzis},
TITLE = {Rhizome Position Paper},
BOOKTITLE = {Proceedings of the 1st Workshop on Friend of a Friend, Social Networking
and the Semantic Web},
YEAR = {2004},
MONTH = {SEPT},
URL = {http://www.w3.org/2001/sw/Europe/events/foaf-galway/papers/pp/rhizome_position_paper/}
}
Slides http://www.aifb.uni-karlsruhe.de/Lehre/Sommer2005/SemTech/stuff/semwiki.ppt
Paper http://www.aifb.uni-karlsruhe.de/Lehre/Sommer2005/SemTech/stuff/semwiki.pdf
http://webseitz.fluxent.com/wiki/SemanticWiki
Adam Souzis, Liminal Systems: Building a Semantic Wiki. in: IEEE Intelligent Systems, September/October 2005 (Vol. 20, No. 5) http://doi.ieeecomputersociety.org/10.1109/MIS.2005.83
Towards a SemanticWikiWikiWeb. ISWC 2004 poster: http://iswc2004.semanticweb.org/posters/PID-LPSVVIIZ-1090243438.pdf

Semantic wikimedia is a project just started (pre-alpha) coupling MediaWiki (the Wikipedia-Software) with semantics (http://meta.wikimedia.org/wiki/Semantic_MediaWiki). AIFB Karlsruhe people have a project on a semantic MediaWiki (http://www.aifb.uni-karlsruhe.de/Projekte/viewProjektenglish?id_db=67)
http://lists.w3.org/Archives/Public/www-html/2005Sep/0002.html talks inter alia about Topic Maps. I have not found more co-citing of Topic Maps and SemWikis.

They want to employ Redland as RDF backend.

There exist topic map-based wikis, z.B. Topiki (http://www.shelter.nu/blog-070.html) or TMWiki by Hendrik Thomas (http://www.topic-maps.org/)

Addition 2005-12-08:
================
IkeWiki is a RDF/OWL-based rewrite of MediaWiki, based on Jena
<http://ikewiki.salzburgresearch.at/>
(Sourceforge: <https://sourceforge.net/projects/ikewiki/> )
<http://jena.sourceforge.net/>

Topic Properties, PSIs and more (Email by Jack Park)

2005-10-13T08:04:00.000-07:00

As a follow-up of informal discussions at TMRA05 in Leipzig with Jack Park on a PSI registry, how difficult this might be with notions in a flux, and what this has to do with subject identification/identity, he today sent an email. I do not fully agree and want to come back soon to this (in a comment). We probably should discuss this at Bernhard Vatant's blog.

In my understanding Jack's main points are:
* Topic Maps can help humans to mediate among heterogeneous populations of ontologies
* we need a working ontology to map most other ontologies
* a lone PSI is not sufficient to unambigously identify a subject among a universe of subjects
* TMRM acknowledges this and allows specifying the properties of subjects
* subject properties means key-value pairs (key-value-valueType or propertyType-value-valueType triples)
* we need PSIs for keys (propertyTypes) and valueTypes (derived from XML dataTypes)
* AI feature vectors might be related to subject properties
* we need a TMA (topic map application) to identify all the ontologies to define the notion of "subject properties"
* the most important aspect of future mapping of subjects with topic maps will be to establish subject identity by way of subject property declarations
* in order to not reinvent terminology, such a TMA should attempt to include all relevant metadata/ontology standards.

Wiki on Topic Maps in Libraries (Suellen Stringer-Hye)

2005-10-13T07:51:00.000-07:00

As announced on topicmapmail, Suellen Stringer-Hye of Vanderbilt University is putting together a Topic Maps for Libraries wiki (with pmwiki) at
<http://tm4lib.library.vanderbilt.edu/wiki/>
and has established a Topic Maps Interest Group within LITA.

Website: http://staffweb.library.vanderbilt.edu/libtech/stringer/
Email: suellen.stringer-hye@Vanderbilt.Edu

Semblogging use case: 40.000 digital fotos of destroyed paintings online

2005-10-10T05:44:00.000-07:00

Reading the article [1] about the 40.000 digital fotos now online from http://www.zi.fotothek.org/, it occurred to me that this might be an interesting user community for semblogging (semantic blogging). I hope to be able to look into providing a first semblogging facility for such users in some weeks.

Unfortunately, the application uses popup windows and not REST style!

[1] "Jetzt online: Hitlers Dia-Sammlung im Netz". Süddeutsche Zeitung, Feuilleton, Freitag 7. Oktober 2005, S. 14

For Semblogging, see my open space presentation slide at TMRA05, included below:

Semblogging with Topic Maps

Motivation
----------
* smart content aggregation of blog entries needs more semantics than just tag clouds
* see e.g. Jack Park‘s elaboration on tagging in his „just for me“ paper
* Semblogging as a special case of semantic annotation in line with DKM (Distributed Knowledge Management)

Prior work
----------
* seminal work by Cayzer (RDF semblogging concept and protoype), citing the XTM book
* redo it, and even better with Topic Maps!
* ideas by Jack Park (on semblogging as an example for Augmented Storytelling)
* idea of Dmitry Bogachev. Prototypical OKS semblogging application by Lars Marius Garshol

Current work
------------
* Developing some Use Cases
* One student implementing in his diploma thesis a prototype coupling blojsom with tmapi and TM engine
* Further work under way looking more into distributed aspects and semantic web services

What to Semblog about?
----------------------
* bibMap or the Topic Map Research and Applications Landscape?
* All TMRA05 participants and community semblogging on Topic Maps? SemWikiBlogging?
* Learning process in a teaching course in information and knowledge management?
[And now added: the collection of 40.000 digital fotos, as discussed above)

Your ideas? Who is interested in what? Who will contribute what?

Towards a P2P(?) PSI registry

2005-10-09T13:32:00.000-07:00

Yes, I advocated a PSI registry in the first open space session of TMRA05.

Lars Marius Garshol had blogged on this:
"Alexander Sigel held a passionate talk about the need for a PSI registry, and really wanted people to help him out. There was vigourous discussion on the subject, and general agreement that this was needed, without anyone really stepping up to pay for it. The subject was eventually deferred to the evening social session."
http://www.garshol.priv.no/blog/8.html

I do not intend to do this myself, but I want to see this happen.

A server from Hetzner starts from 39 EUR/month. http://www.hetzner.de/
Maybe we could use some PSI work from Morpheus? http://www.mssm.nl/

I agree with Jack Park that not all subjects have stable notions ("are in a flux"), and that a sophisticated PSI registry concept would have to deal with this. Upper categories are more stable, and the notions are stable at the time of describing the PSI. How can we include the (knowledge organizational) characteristics of a concept from its definition in the PSI? How are they related to topic characteristics in establishing identity?

Maybe we could have the domain psi-registry.net registered on the Norwegian Topic Map association?
(Sorry, last night I had mistyped topicmap-registry.net here. Of course this should be RDF-friendly!)

Here is my slide:
http://www.informatik.uni-leipzig.de/~tmra05/PRES/ASa.pdf

> Motivation
* Better semantic interoperability with PSI identity. Merging. SLUO (collocation objective)
* Reuse. Best Practice. Distributed Knowledge Management (DKM). Federated Seamless Knowledge
* Infrastructure for emerging collaborative distributed lightweight ontology engineering
* No long-term, public registry („PSIpedia“) existing. Wikipedia not the full solution for PSIs!
* No working group on this, not much progress seen since the inception of XTM
> Some Use Cases
* Has someone published a PSI for the topic I want to make an assertion about?
* Has someone published a set of PSIs for the type of topic I want to make an assertion about?
* (How) could I reuse an existing, even 3rd party Knowledge Organization Schema (upconvert, proxify)
* How to handle: deletion? Update/newer versions?
* Assess not only identity, but thesaurus-like relations
* Provide a pointer to a information or service offer (like a sample chapter of a book)
> Architectural and Technical Issues
* How to avoid the „arbitrary proliferation of PSI entries, or even PSI registries“?
* P2P or central? TMRAP?
* Replication?
* TM engine backend? Querying? Search engine?
> Implementation and Organization
* Sourceforge project? Language? Hosting of the application? Responsibility?
> Cooperation with content owners
* Creative Commons Licencing vs. What‘s the incentive for publishers/content producers?
> Trust Networks
* Scope? Values? like in P2P Trust Networks?
> Who is interested in what? Who will contribute what?

---
Addition 2005-11-28:
Today, Michael Chapman has hinted me to his PSI registry:
http://psi.mchapman.com/vl/

Probabilistic Datalog and tolog

2005-10-09T12:46:00.000-07:00

The TMRA05 presentation of a TM application framework by Naito-san made me mention "probabilistic datalog" because I think this might be relevant to fuzzy Topic Maps retrieval with tolog-like languages.

Lars Marius Garshol blogged my remark right away:
"In the questions Alex Sigel brought up something I think was called "probabilistic Datalog", which is used in information retrieval. That sounded quite relevant, and interesting. I may need to do some digging on that. "
http://www.garshol.priv.no/blog/8.html

A decade ago, Prof. Norbert Fuhr had extended Datalog to Probabilistic Datalog.
In turn it had been extended for usage with DAML+OIL, OWL's predecessor.

Here some references:
http://doi.acm.org/10.1145/215206.215372
http://citeseer.ist.psu.edu/17554.html
For implementing the logical model of databases, a variant of Horn logic called Datalogis widely used. Regarding IR as generalization of database retrieval, it seems quite naturalto develop a probabilistic version of Datalog.

Norbert Fuhr: Probabilistic Datalog: Implementing Logical Information Retrieval for Advanced Applications Journal of the American Society for Information Science JASIS 51:2 (Jan 2000), 95

@incollection{Roelleke/Fuhr:98a,
author={Thomas R{\"o}lleke and Norbert Fuhr},
title={Information Retrieval with Probabilistic {Datalog}},
chapter=9,
pages={221--245},
crossref={LOGICIR:98},
entrydate=19971028,
key={Roelleke/Fuhr:98a},
year=1998,
}

http://www.is.informatik.uni-duisburg.de/bib/pdf/ir/Nottelmann_Fuhr:04a.pdf