# LOGO: Logics for Ontologies

Lead Research Organisation: University of Manchester
Department Name: Computer Science

### Abstract

Ontologies help both humans and computer applications to communicate by providing a vocabulary of terms together with formal and computerprocessable descriptions of their meanings and the relationships between them. They play a major role in the next-generation World Wide Web (known as the Semantic Web), where they are used to describe the content of Web resources, with the aim of both Improving search for human users and making it easier for computer programs to exploit the vast range of information that is available on the Web. Ontologies are also widely used to define specialised vocabularies for use in medicine, biology and other scientific disciplines.Ontologies are usually developed by human experts, but even for experts the job of defining all the relevant terms is a difficult and time consuming one. It is therefore important to provide intelligent tools that support ontology designers. For this reason, many ontology languages, including OWL (the standard language used for Semantic Web ontologies), are based on logics, This provides a formal specification of the meaning of the language and allows tools to use automated reasoning systems, e.g., to check that Interactions between descriptions do not lead to logical contradictions. Reasoning systems are also useful when ontologies are deployed in applications, where they could be used, e.g., to determine which Web pages match a search request that uses terms defined In an ontology.The central role of ontologies in the above mentioned applications brings with it, however, requirements for expressive power and reasoning support which are beyond the capabilities of existing ontology languages and reasoning systems. For example, OWL cannot express the fact that the brother of a persons father is also their uncle, and even for OWL, no practical reasoning system is yet available. Moreover, existing reasoning systems often have difficulties dealing with the very large ontologies that are needed in many realistic applications. The research described in this proposal aims at bridging this gulf between requirements and capabilities; its ultimate goal is the development of logics and reasoning techniques that that will form the foundations of the next generation of ontology languages and reasoning systems.The research programme will be made up of three complementary strands. The first strand will focus on existing ontology languages, and the logics on which they are based. The aim will be to devise principaled extensions of these ontology languages that meet expressive requirements that have been identified in application areas such as medicine and the Semantic Web.The second strand will focus on implementation techniques for existing ontology languages and for extended languages developed in the first strand. The aim will be to develop highly optimised reasoning systems capable of supporting both the design and deployment of ontologies in large scale applications.The third strand will focus on very expressive ontology languages. These languages are based on logics where it is known to be impossible to build a reasoning system that can solve any problem, e.g., one that is guaranteed to detect all possible contradictions. The aim is to develop reasoning systems that will still be able to efficiently solve the vast majority of problems derived from the use of ontologies in applications.Finally, in order to ensure that the logics, algorithms and reasoning systems being developed really do meet application requirements, they will be tested and evaluated in cooperation with ontology designers and developers of ontology based applications.

### ORCID iD

Ian Horrocks (Principal Investigator)

### Publications

10 25 50
Horrocks I (2008) Ontologies and the semantic web in Communications of the ACM

Horrocks I (2007) A Tableau Decision Procedure for $\mathcal{SHOIQ}$ in Journal of Automated Reasoning

Sattler U (2008) Conjunctive Query Answering for the Description Logic SHIQ in Journal of Artificial Intelligence Research

Tsarkov D (2007) Optimizing Terminological Reasoning for Expressive Description Logics in Journal of Automated Reasoning

### Related Projects

Project Reference Relationship Related To Start End Award Value
EP/C543319/1 01/03/2006 31/08/2007 £369,194
EP/C543319/2 Transfer EP/C543319/1 01/09/2007 28/02/2011 £262,852

Description The research carried out in this project exerted a considerable influence on the development of the semantic web in general and of ontology languages in particular, where I played a key role in the development of a series of description logic based ontology languages. I recently chaired the W3C working group that developed OWL 2, a successor to the W3C's OWL ontology language standard. OWL 2 is based almost entirely on my research into Description Logics, decision procedures, reasoning systems and the application of all of the above in ontology languages and tools. OWL 2 also extends OWL with tractable profiles based on key works within the DL community, notably work on the DL-Lite and EL families of tractable DLs. Thus I have succeeded in disseminating a range of important research results from across the DL community and greatly increasing their influence on practical applications.

Regarding basic research in DLs, numerous important results have been achieved during the course of the project. Most important of these was my work on developing decision procedures for SHOIQ and SROIQ. These logics form the core of OWL 2, and the combination of nominals, inverse and counting (the OIQ part) makes the design of a decision procedure particularly tricky. In fact the decidability of this logic was an important open problem for several years. I showed that it is decidable, but that it has a much more complex model structure in which the non-tree part of the model is not restricted to the ABox. I devised a new technique for constructing such models by introducing new ABox individuals as needed.

Regarding optimisation techniques and reasoning systems, working with Boris Motik and others I developed a new Hypertableau reasoning technique for SROIQ, implemented it in the HermiT system, and devised a whole range of new optimisation techniques. HermiT is now the standard reasoner distributed with Stanford's Protege ontology development environment, and as such is being used by thousands of ontology developers around the world. The techniques developed in HermiT and in my earlier FaCT and FaCT++ systems are also the basis for all the sound and complete OWL reasoning systems known to me.

In addition to the above, I have worked on a range of other problems in the KR area. With Cuenca Grau, Kazakov and Sattler I developed theory and practical techniques for modularising ontologies, something for which only ad hoc techniques had previously been available. With Glimm and Lutz I developed query answering techniques for expressive DLs solving, e.g., the open problem as to the decidability of conjunctive query answering for SHIQ. With Grosof, Patel- Schneider and others I developed a variety of techniques for integrating rules with DLs and DL based ontology languages, with our papers on DLP and on SWRL still being amongst the most highly cited in this area. With Cuenca Grau and Stoilos I have recently been working on the systematic evaluation of incomplete reasoning techniques, and our paper on this topic won a distinguished paper award at AAAI last year.

The influence of this work can be gauged from citation counts and from the number of invited keynotes that I have given in recent years. Regarding the former, according to google scholar, my h-index is 74, and my work has been cited more than 26,000 times. Regarding the latter, I have given more than 40 keynote talks and invited seminars, and in 2010 alone I gave keynotes at the DL, KR, ICDT/EDBT, ECAI and KSEM conferences, as well as giving seminars at Oracle Inc, and at Stanford, Nanjing and Zhejiang universities.
Exploitation Route The OWL standard(s) are widely used in industry and research (both academic and commercial).
Sectors Digital/Communication/Information Technologies (including Software)

Description EPSRC
Amount £572,891 (GBP)
Funding ID EP/E03781X/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start 09/2007
End 08/2010

Description EPSRC
Amount £704,521 (GBP)
Funding ID EP/H051511/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start 04/2011
End 09/2014

Description EPSRC
Amount £704,521 (GBP)
Funding ID EP/H051511/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start

Description EPSRC
Amount £359,707 (GBP)
Funding ID EP/G02085X/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start

Description EPSRC
Amount £480,412 (GBP)
Funding ID EP/F065841/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start

Description EPSRC
Amount £359,707 (GBP)
Funding ID EP/G02085X/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start

Description EPSRC
Amount £480,412 (GBP)
Funding ID EP/F065841/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start

Description EPSRC
Amount £572,891 (GBP)
Funding ID EP/E03781X/1
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Sector Public
Country United Kingdom
Start

Description Chair of W3C OWL Working Group
Organisation World Wide Web Consortium
Country United States
Sector Charity/Non Profit
PI Contribution Chair of W3C OWL Working Group
Start Year 2007