Ontolog Forum

Ontolog Invited Speaker Presentation - Professor Ian Horrocks - Thu 2010.07.22

  • Session Host: Dr. LeoObrst (Ontolog; MITRE)
  • Invited Speaker: Professor IanHorrocks (University of Oxford)
  • Presentation Title: "Scalable Ontology-Based Information Systems"

Conference Call Details

  • Date: Thursday, 22-July-2010
  • Start Time: 6:30pm BST / 10:30am PDT / 1:30pm EDT / 7:30pm CEST / 17:30 UTC
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  • Regrets:
    • Douglas Donahue (PCL Institute) ... will catch this from the archives
    • Steve Ray

Agenda & Proceedings

  • Session Format and Agenda:
    • this will be virtual session over a phone conference setting, augmented by in-session chat and shared computer screen support
    1. The session will start with a brief self-introduction of the attendees (~15 min.) [We will be skipping this if there are more than 20 participants.]
    2. Introduction of the invited speakers - session chair: Leo Obrst
    3. Presentation by our invited speakers - Ian Horrocks (~60 min.)
    4. Q&A and Open discussion (~15 min.) [Kindly identify yourself before speaking.]
  • Presentation Title: "Scalable Ontology-Based Information Systems" [ Professor Ian Horrocks ]
  • Abstract:
Ontologies and ontology based systems are becoming increasingly

important in meeting the demand for more powerful and flexible information systems. Requirements for such systems include the need to deal with incomplete and semi-structured information, to integrate information from heterogeneous sources, to employ richer and more flexible schemas, and for query answers to reflect both knowledge and data. Provision of such enhanced capabilities must, however, be in addition to, and not instead of, the well-established features of existing database systems, in particular their robust scalability. Achieving this is, of course, extremely challenging. In this talk I will present some recent research efforts that tackle this problem, including investigations of tractable fragments, new algorithmic techniques, new optimisations and the exploitation of relational database technology.

  • About the Speakers:
Ian Horrocks is a Professor in the Oxford University Computing Laboratory where he jointly (with Georg Gottlob) leads the Information Systems Group. His research interests include knowledge representation, ontologies and ontology languages, modal and description logics, automated reasoning, implementation and optimisation of reasoning systems, and applications in areas such as e-Science and the Semantic Web. He was centrally involved in the development of the OIL, DAML+OIL and OWL ontology languages, and was co-chair of the W3C Working Group that recently developed OWL 2. He also developed algorithms and implementation techniques that are employed in many reasoning systems, and implemented the well known FaCT system in which many of these algorithms and implementations techniques were first deployed. He has published more than 150 articles in conferences, journals and books (see, many of which are highly cited, and has given more than 40 keynote and invited talks. He is a BCS Fellow, an ECCAI Fellow, an EPSRC Senior Research Fellow and a past winner of the BCS Roger Needham award.

Transcript of the online chat during the session

see raw transcript here.

(for better clarity, the version below is a re-organized and lightly edited chat-transcript.)

Participants are welcome to make light edits to their own contributions as they see fit.

-- begin of chat session --

Peter P. Yim: .

Welcome to the Ontolog Invited Speaker Presentation - Professor Ian Horrocks - Thu 2010.07.22 (2EQX)

  • Session Host: Dr. Leo Obrst (Ontolog; MITRE) (2F37)
  • Invited Speakers: Professor Ian Horrocks (University of Oxford) (2F3
  • Presentation Title: "Scalable Ontology-Based Information Systems" (2F39)

Please refer to details on session page at:


anonymous morphed into Ian Horrocks

anonymous morphed into Julita Bermejo-Alonso

anonymous11 morphed into Mike Hewett

anonymous1 morphed into Peter Chan

anonymous2 morphed into Jess Turner

anonymous3 morphed into Elisa Kendall

Ian Horrocks: Slides are at:

anonymous3 morphed into Sina Madani

anonymous6 morphed into Fabian Neuhaus

anonymous1 morphed into Guoqian Jiang

anonymous7 morphed into Mikhail Soutchanski

anonymous1 morphed into Pierluigi Miraglia

anonymous6 morphed into Amanda Vizedom

anonymous31 morphed into Bobbin Teegarden

anonymous3 morphed into Cui Tao

anonymous4 morphed into Peter Wagner

anonymous6 morphed into Melanie Courtot

anonymous1 morphed into Pavithra Kenjige

anonymous7 morphed into Sudarsan Rachuri

anonymous4 morphed into Donald Kretz

Arturo Sanchez: LOL

{{{ { ... dog barking in the background ... (laughs) } }}} }}}

Joel Bender: The place is going to the dogs!

Ian Horrocks: As a DL person I am well used to that sort of response

anonymous11 morphed into Mark Johnson

anonymous5 morphed into Peter Bruhn Andersen

anonymous1 morphed into Elizabeth Florescu

anonymous6 morphed into MyCoyne

John Singer: trying to download the pdf, but its going slow

Pierluigi Miraglia: Hi Amanda & Peter

Amanda Vizedom: Hello Pierluigi, good to see you here.

anonymous6 morphed into Rob Hausam

anonymous7 morphed into Marcia Zeng

anonymous3 morphed into Ravi Sharma

Frank Chum morphed into Frank Chum

anonymous5 morphed into Simon Spero

Todd Schneider: Peter, Ian is fading in and out.

Arturo Sanchez: OK here ...

John Singer: ok here

Michael Riben: ok here

Clarence Dillon: ok here.

Mike Hewett: Sounds pretty good to me. A little weak. But no fading.

anonymous1 morphed into Lynn Leitte

anonymous4 morphed into Bruce Peoples

anonymous3 morphed into Jae Hyun Lee

Michael Riben: what slide is he on?

Eric Chan: slide 12

Michael Riben: okay..thanks

anonymous1 morphed into Anantha Narayanan

Arturo Sanchez: @Prof. Horrocks: Although the ontologies are not what the systems are supposed to do,

but what the data the systems will use are all about. Do you agree with this?

Amanda Vizedom: Comment for discussion later, perhaps: Ian, you've just remarked (on slide 12) that

you see the low complexity of DLs as desirable from a performance perspective, and from a

perspective I might paraphrase as tractability of representation (degree to which tiny changes

ripple out in changes not easily anticipated). This may be true on very small, narrow domain,

controlled representation spaces. In my experience, however, the actual result of KR language

simplicity is more complex, and often the opposite. In complex, RW problem-driven representation, a

lower-expressivity language is *at best* like a logical language with only 3 minimal operators. In

theory, you can represent whatever you need; in practice, doing so may require extraordinarily

complex expressions and mental contortions. In the ontology case, lower expressivity has a

significant cost, increasing with number of collaborators or users and with scale of task. The more

ontologists have to stretch the language extra-ordinarily, the worse performance becomes and the

more problems arise for collaboration and interoperation. Have you considered this cost of

low-expressivity, as in DLs? Have you seen DLs used for very large scale and/or broad domain real

world cases?

Bill Hogan: perhaps it's only an artifact of my medical training, but I don't think of all heart

diseases as being a subtype of vascular disease.

Frank Chum: There are s lot of business cases for the O&G industry in ontology-based information


Sudarsan Rachuri: How to we define a notion of quality for ontology?

Cory Casanave: These are good real world examples. As you said, the real world and our understanding

is not perfect. Can you speak to the fragility of description logics in the face of a less than

perfect ontology.

Frank Chum: Does OWL 2 has Full/Lite DL for complexity and computability?

Leo Obrst: Ian, along the lines of Amanda's question, some believe that there are 2 problems related

to KR expressiveness: 1) having a rich enough expressiveness in your modeling/KR language to express

what you need to for your domain, and 2) having an efficient enough representation to do automated

reasoning in near real time. And so folks think that you need: A) a FOL expressive language for

representing your ontology, B) a knowledge compilation process to transform (A) to (C), probably

losing information, and C) an efficient runtime representation that enables fast automated

reasoning. Some say that DLs try to shoehorn the (1) and (2) language into the same language, and so

there is no B.

Amanda Vizedom: Another question about the DL expressivity trade-off: How common is it, really, to

have a sufficiently complex and demanding case that completeness and decidability are going to be

serious issues, and yet *not* need to create constraints that terminate queries and inference well

before the "some finite amount of time" in which decidable systems can guarantee results?

Todd Schneider: Ian, how do implementations of tableau algorithms make use of logical independence?

Peter P. Yim: we've skipped from slide 31 to slide 50 ... now at slide#51

Peter P. Yim: skipping to slide#68

Peter P. Yim: skipping to slide#72

Michael Grüninger: What is the citation for the experiments in slide 68? What were the

queries/reasoning problems? Were all of the ontologies written in EL?

Peter P. Yim: @Michael, if you can locate the literature Ian referred us to, would you kindly paste it

onto this chat board, please

Michael Grüninger: @Peter: The citation I was looking for is: Consequence-Driven Reasoning for Horn

SHIQ Ontologies by Yevgeny Kazakov ... In Proceedings of the 21st International Conference on

Artificial Intelligence (IJCAI 2009). Pages 2040-2045. , 2009.

Peter P. Yim: @MichaelGruninger - thank you, Michael

Peter P. Yim: skipping to slide#89

Leo Obrst: Does saturation include quick computation of subsumption ala Ait-Kaci et al's methods,

i.e.,optimal hierarchical encoding of types in bit encodings, prime numbers, etc.?

Leo Obrst: oops.

Mike Hewett: What slide is Ian on?

Arturo Sanchez: 89

Peter P. Yim: @JimDisbrow ... we are holding off Q&A until the prepared presentation is through ... you

can try capturing your question on the chat-board as a placeholder for now

anonymous morphed into Jim Disbrow

Amanda Vizedom: OWL 2 question for later, unless you answer it anyway before then: Slide #53, the

profiles are distinguished by whether they are optimized for size of ontology or size of data sets.

But of course, size is not the only major distinction in application contexts. Prior versions of OWL

have proven much more or less usable depending on a variety of other application context

characteristics, e.g.: complexity and variety of relationships to be represented; whether use is

within a single domain/community or crosses multiple domains/communities; complexity of reasoning

required (mostly subsumption or not, for example); whether the ontology is used to represent

instance-level data or to represent, at a meta-level, the semantics of data stored elsewhere, or

both; whether the ontology must support machine usability, human usability, or both, and so on. Were

these and other features of the (increasingly varied!) variety of ontology applications considered

in the development of OWL 2? If so, what were some of the effects on the final form of the language?

Peter P. Yim: will the "anonymous" participants please click on the "Settings" button (top center) and

morph into your real name, so we can tell who you are, and properly attribute your contributions

anonymous1 morphed into Kathy Ellis

Stavros Macrakis: Is OWL 2 QL expressive enough to handle arbitrary-length chains, e.g. "A is a

direct or indirect ancestor of B"?

Pierluigi Miraglia: Question on QL: is the optimization expected for general inference engines, or

only if reasoning is delegated to RDBMS? I.e., do I see a gain if I use OWL QL in a Pellet or FaCT

based application?

John Singer: how is IBM involved in this?

Arturo Sanchez: @Prof. Horrocks: can you mention classes of problems for which OWL 2 is particularly

good for, and also classes of problems for which OWL 2 is particularly bad for?

Sudarsan Rachuri: How to we define a notion of quality for ontology?

Amanda Vizedom: Slide #96: Indeed, the infrastructure mentioned regarding privacy and information

hiding is partially overlapping with infrastructure needed for a variety of kinds of KR and

management of ontology content. Provenance issues are important in many interoperability

applications; cross-community uses may also call for considerable capture of knowledge relevant to

dynamically selecting relevant ontology content. Many people have resorted to reification of triples

for this. Others have built complicated containers for pre-defined contexts and ways of moving

between them. None of that has been great. Does OWL 2 significantly improve on this?

Stavros Macrakis: I have to get off the call -- Pierluigi Miraglia will follow up on my question.

MyCoyne: hello

Arturo Sanchez: Great session. Thank you!

Todd Schneider: I also need to leave for another meeting around 3 PM EDT.

Sudarsan Rachuri: Thanks for the excellent presentation. Bye

Amanda Vizedom: Will ask this, but capturing to chat as well: Excellent point about mismatch between

OWL "constraint" behavior and what most people think of as "constraint-checking." Any comment on use

of SPARQL and other query languages to off-load some of these features and requirements to another


Peter P. Yim: please hold off "OWL 2" specific questions until our two "OWL 2" sessions next Thursday

and the following one

Cory Casanave: Follow up on fragility: Your response assumes an ontology under a single authority -

in a federated knowledge base this is not practical. Can DL be used in an open, federated

environment like the web.

Amanda Vizedom: Follow-up to Cory's question: Indeed, I think much of the high payoff work in

semantic interoperability -- even across communities and data sources within a single, large

enterprise -- is a federated, not singly-controlled environment. Ontologies can be and have been

used to enable more and better information sharing in such cases. But this requires considerable

richness of representation to make contextual assumptions explicit, as well as considerable

provenance and other metadata. This is a significant motivation for my earlier questions.

Cory Casanave: My mike did not seem to work; I am wondering how Ian responds to Benjamin Grosof's

assertion that a rule system is more capabile in an onology that may have local inconsistancies, and

that such inconsistencies are inevitable - even in a selected subset of "the web".

Amanda Vizedom: Strong second to Brian's follow-up about reasoning about provenance. Annotations are

not sufficient, and one does indeed need to represent relevant provenance details and reason about

them as relevant to specific uses or users. The folks creating the data in once source are not going

to conveniently note that their data doesn't meet the standards of my need. But an intermediate

infrastructure can reason about whether their data meets my provenance requirements.

Joel Bender: An outstanding session, thank you!

Cory Casanave: Thanks you so much!

Frank Chum: Great session. Thank you!!!

Amanda Vizedom: Thank you, Prof. Horrocks. I look forward to the next two sessions.

Peter P. Yim: Great talk ... thank you VERY much, Professor Horrocks

Peter P. Yim: Thank you all for your participation

Peter P. Yim: Look forward to having all of you back here in the next two weeks, when Professor Horrocks

will lead the two "OWL 2" sessions, see

... drop me a note (rsvp to <>) if you are coming

and haven't registered for those sessions yet, please

Peter P. Yim: @ALL: if what we do at ONTOLOG aligns well with your professional interest, join the

community if you are not already a member of Ontolog - see:

Ian Horrocks: Thanks to everyone for listening. Look forward to talking to you again next week.

Peter P. Yim: - session ended 12:31pm PDT -

-- end of chat session --

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  • Conference Date and Time: 22-Jul-2010 10:39am ~ 12:31 pm PDT
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