AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 1 Mind the Web! Valentin Zacharias, Andreas Abecker, Imen Borgi, Simone Braun, Andreas Schmidt FZI Karlsruhe, Germany Denny Vrandečić AIFB, Universität Karlsruhe (TH), Germany Workshop on new forms of reasoning for the Semantic Web: scalable, tolerant and dynamic Busan, Korea November 11, 2007

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 2 Thesis Not taking the web in Semantic Web serious has lead many Semantic Web researchers to do Semantic Systems and reasoning research without trying to tackle the fundamental challenges of the Semantic Web.

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 3 Overview Hypotheses Current trends and misconceptions Problems Some solutions

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 4 Hypotheses 1. Web scale is not just a bit larger 2. Ontologies are always changing 3. There is no right ontology

Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 5 A triple

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Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 10 OWLIM 10 7 Triples [29] Suez Canal

Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 11 RDF Store subsecond querying 10 8 Triples [25,26] Moon Fensel / Harmelen estimate Triples

Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 12 ~10 9 Triples Earth Fensel / Harmelen estimate Triples

Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 13 Jupiter Fensel / Harmelen estimate Triples ~10 10 Triples

Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 14 Fensel / Harmelen estimate Triples ~10 11 Triples

Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 15 Distance Sun – Pluto Fensel / Harmelen estimate Triples ~10 14 Triples

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 16 Hypotheses 1. Web scale is not just a bit larger 2. Ontologies are always changing 3. There is no right ontology

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 17 Dynamics of Web edits in Wikipedia 200 tags in del.icio.us 270 image uploads to flickr 1100 blog entries per minute! No reason to believe the Semantic Web will be any less dynamic – rather more!

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 18 Reasons for change Error correction New information Change of view Change of the world None of these reasons will disappear

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 19 Hypotheses 1. Web scale is not just a bit larger 2. Ontologies are always changing 3. There is no right ontology

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 20 There is no right ontology Many different views Conflicting views and interests Semantic desktop -> many ontologies Ontologies are abstractions Different tasks lead to different ontologies Many design choices Google Base: schemas Intentionally false (Spam)

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 21 Misconceptions 1. Classical reasoning approaches will be used on the web 2. Assumption of correctness 3. It is a logical web, not a statistical one

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 22 Making weaker languages Reducing the expressive power of a logic does not solve any problems faster; its only effect is to make some problems impossible to state. John Sowa

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 23 Classical Reasoning Approaches Even Polynomial is much to slow, unless a subset of statements is retrieved first Identifying this subset can be non trivial and is at the core of the challenge posed by the Semantic Web

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 24 Classical Reasoning Approaches – Focus theoretical worst cases Undecidability – may be harmless in all cases that matter, completeness unachievable in practice anyway Worst Case complexity – may be a bad guidance for usefulness. Harmelen 2006

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 25 Assumption of correctness Reasoning is always on perfect statements Dealing with imperfection is preprocessing Vagueness Uncertainty Intentionally false Errors Outdated

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 26 A logical web Repeating a statement does not make it more true

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AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 29 Web Data Aggregation Statistical aggregation necessary for opinions Important in Information Retrieval (see PageRank)

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 30 A logical web Repeating a statement does not make it more true But more likely Rules in news: three sources for a story Counting and relations matter Combine this with reasoning

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 31 Solutions?

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 32 See paper for more More approaches to reasoning KB partitioning and summarizing Approximate reasoning Massive parallelization Special purpose reasoners Deductive database techniques Combine retrieval and reasoning Emergence of Semantics Ontology Maturing Change on the Semantic Web

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 33 Conclusions Many promising approaches But which one to choose? Use cases are needed most! To evaluate the approaches To point into the right direction This is why this workshop is here…

AIFB Denny Vrandečić – AIFB, Universität Karlsruhe (TH) 34 Thank you! Not taking the web in Semantic Web serious has lead many Semantic Web researchers to do Semantic Systems and reasoning research without trying to tackle the fundamental challenges of the Semantic Web.