LKIF Core

LKIF Ontology Base URI 
http://purl.org/net/lkif-core
LKIF Extended Base URI 
http://purl.org/net/lkif-extended

The LKIF Core ontology provides a vocabulary and a set of standard definitions of concepts common to all legal fields (See Breuker et al., 2007; Hoekstra et al., 2007, 2008), , and consists of 15 modules, each of which describes a set of closely related concepts from both legal and commonsense domains. It was developed within the ESTRELLA project, as part of the Legal Knowledge Interchange Format (LKIF). In several papers, we identified three main ways for a legal core ontology to facilitate information exchange in LKIF. First of all, the ontology can serve as a resource for special, legal inference. Secondly, the definitions of terms in the ontology can facilitate knowledge acquisition, a terminological framework can facilitate the exchange of knowledge across multiple knowledge bases, and lastly it can be a basis for semantic annotation of legal information sources (See the extended description).

Besides meeting the general requirements for knowledge representation ontologies outlined in Hoekstra (2009), the ontology contains a core set of definitions for describing specific legal terms. Law can be viewed as an instrument used by the legal and political system to identify and control situations and events in social interaction. By far the bulk of social situations, be it in our family life, at work, related to transport, property, crime, etc. is not described in specialised technical terms: their meaning is part of common sense. For instance, the conflicts and problems brought to court – legal cases – are initially described using common sense terms, and are gradually translated into legal technical terminology in the process of coming to a decision. For this legal qualification to be possible, the gap between the vocabulary of a case and legal terminology needs to be bridged. The possibility of legal qualification in general – by legal professionals – is a strong indication that the vocabularies of legal knowledge and common sense are not disjoint. Legal terminology can be reduced to the actual societal events and states governed by law. In other words, the basic categories of the LKIF ontology reflect the view that legal world knowledge is an abstraction of common sense.

A third requirement for LKIF is given by the ideal of the Semantic Web to achieve understanding both between web services and between human users. In fact, a commonsense perspective is also applicable to any serious endeavour towards a Semantic Web. As the the web is about the most diverse information source we know today, a common sense oriented ontology is an important first step to more uniform web-based knowledge representation. Conversely, the distribution of legal information across various strongly interconnected sources is a demanding use case for semantic web technology (Hoekstra, 2008). An important feature of the LKIF Core ontology is therefore that it is represented wholly using the DL profile of OWL 2.

Information

Loading the Ontology

Contact

Problems? Questions? Suggestions? Please contact Rinke Hoekstra at hoekstra@uva.nl.

Reading Material

  • Rinke Hoekstra, Ontology Representation - Design Patterns and Ontologies that Make Sense. PhD Thesis, under review, 2009.
  • Rinke Hoekstra, Joost Breuker, Marcello Di Bello, and Alexander Boer. LKIF core: Principled ontology development for the legal domain. In Joost Breuker, Pompeu Casanovas, Michel Klein, and Enrico Francesconi, editors, Law, Ontologies and the Semantic Web, Frontiers of Artificial Intelligence and Applications. IOS Press, Amsterdam, 2009.
  • Rinke Hoekstra. Use of OWL in the legal domain (statement of interest). In Kendall Clark and Peter F. Patel-Schneider, editors, Proceedings of OWL: Experiences and Directions (OWLED 2008 DC), Washington, DC (metro), April 2008. .pdf
  • Szymon Klarman, Rinke Hoekstra, and Marc Bron. Versions and applicability of concept definitions in legal ontologies. In Kendall Clark and Peter F. Patel-Schneider, editors, Proceedings of OWL: Experiences and Directions (OWLED 2008 DC), Washington, DC (metro), April 2008. .pdf
  • Rinke Hoekstra, Joost Breuker, Marcello Di Bello, and Alexander Boer. The LKIF Core ontology of basic legal concepts. In Pompeu Casanovas, Maria Angela Biasiotti, Enrico Francesconi, and Maria Teresa Sagri, editors, Proceedings of the Workshop on Legal Ontologies and Artificial Intelligence Techniques (LOAIT 2007), June 2007. .pdf
  • Joost Breuker, Rinke Hoekstra, Alexander Boer, Kasper van den Berg, Rossella Rubino, Giovanni Sartor, Monica Palmirani, Adam Wyner, and Trevor Bench-Capon. OWL ontology of basic legal concepts (LKIF-Core). Deliverable 1.4, Estrella, 2007. .pdf

License

The LKIF-Core ontology is released under the GNU Lesser General Public License. For details about this license, please visit http://www.gnu.org/licenses/lgpl.html.

Description

Roles in Information Exchange

LKIF Core supports information exchange in four ways:

Resource for Special, Legal Inference:: Typical and abstract legal concepts are often strongly interrelated and thereby provide the basis for computing equivalencies, or paraphrases, and implications. For instance, by representing an obligation as the opposite of a prohibition, a (legal) knowledge system can make inferences that capture the notion that they are each others’ inverse. A prohibition leaves all options open – except the one that is forbidden – while an obligation is unavoidable when all its requirements, or conditions, are satisfied. Although this implicit knowledge is relevant when reasoning with norms and cases, it does not express the control knowledge of reasoning (as in problem solving methods), but merely elicits the implications of declarative definitions. Specialised legal inference can be based on definitions of concepts in an ontology: an inference engine can generate the implied consequences of explicit concept definitions. A classical example of specialised inference using the definitions in an ontology and a (general) inference engine is temporal reasoning based on Allen (1984)’s ontology of time (See the time module). To enable special inference, terms should be highly interrelated and form a coherent cluster with little or no external dependencies (cf. The Second Naive Physics Manifesto of Hayes (1985)). An example of such a cluster in the legal domain is that of the terms that denote deontic qualifications. Clusters of this type are usually found at very high levels of abstraction.

Knowledge Acquisition Support:: The classical use of both top and core ontologies in knowledge representation is as a means to support knowledge acquisition. If well designed and explained, they provide an initial structure to which domain terms can be attached as subclasses. Inheritance of properties and other implicit knowledge can then be used to check not only consistency, but also the extra-logical quality of the ontology: whether what is derived (classes, properties) makes sense. The use of a core or top structure that has well tested and evaluated implications, makes it easier to check whether domain refinements are not only consistent, but also arrive at inferences that correspond to what the knowledge engineer or user holds to be valid. The knowledge acquisition support of ontologies is not restricted to just ontological or even terminological knowledge.

Preventing Loss in Translation:: A legal ontology can play an important role in the translation of existing legal knowledge bases to other representation formats. In particular when these knowledge bases are converted into LKIF as the basis for articulate knowledge serving. Similar to a translation between different natural languages, a formal, ‘syntactic’ translation may clash with the semantics implied by the original knowledge representation. An ontology, as representation of the semantics of terms, allows us to keep track of the use of terms across multiple knowledge bases.

Resource for Semantic Annotation:: The semantic annotation of legal sources, such as regulations and jurisprudence is an important contribution to the accessibility and maintainability of these sources. First of all, an ontology can be a source for information retrieval. Secondly, the status of an officially sanctioned legal text is primarily determined by its relation to other legal texts (Boer et al., 2004, see http://www.metalex.eu ). This status can be made explicit by expressing it using ontologically defined relations. In fact, these relations do not just hold between the texts themselves, but between the formal representations of their content as well (Klarman et al., 2008).

Module Description

Abstract Concepts

Most abstract concepts are defined in five closely related modules: top, place, mereology, time and spacetime.

  • top The LKIF top ontology is largely based on the top-level of LRI-Core but has less ontological commitment in the sense that it imposes less restrictions on subclasses of the top categories.
  • place The place module partially implements the theory of relative places (Donnelly, 2005) in OWL DL.
  • mereology The mereology module defines mereological concepts such as parts and wholes, and typical mereological relations such as part of, component of, containment, membership etc.
  • time The time module provides an OWL DL implementation of the theory of time by Allen (1984).

Basic Concepts

Basic-level concepts are distributed across four modules: process, role, action and expression.

  • process The process module extends the LKIF top ontology module with a definition of changes, processes (being causal changes) and physical objects. It introduces a limited set of properties for describing participant roles of processes.
  • role The role module defines a typology of roles (epistemic roles, functions, person roles, organisation roles) and the plays-property for relating a role filler to a role.
  • action The action module describes the vocabulary for representing actions in general. Actions are processes which are performed by some agent (the actor of the action). This module does not commit itself to a particular theory on thematic roles.
  • expression The expression module describes a vocabulary for describing, propositions and propositional attitudes (belief, intention), qualifications, statements and media. It furthermore extends the role module with a number or epistemic roles, and is the basis for the definition of norms.

Legal Concepts

These basic clusters are extended by three modules that form the legal ontology: legal action, legal role and norm.

  • legal-action The legal action module extends the action module with a number of legal concepts related to action and agent, such as public acts, public bodies, legal person, natural person etc.
  • legal-role The legal role module extends the role module with a small number of legal concepts related to roles, legal professions etc.
  • norm The norm module is an extension primarily on the expression module where norms are defined as qualifications. Please refer to Deliverable 1.1 for a more in-depth description of the underlying theory. It furthermore defines a number of legal sources, e.g. legal documents, customary law etc., and a typology of rights and powers, cf. Sartor (2006), Rubino et al. (2006)

Framework Modules

In addition to these legal clusters, two modules are provided that cover the basic vocabulary of two frameworks: modification and rules.

  • modification The modification module is both an extension of the time module and the legal action module. The time module is extended with numerous intervals and moments describing the efficacy and being in force of legal documents. The action module is extended with a typology of modifications. These concepts are described in further detail in Deliverable 3.2 of the ESTRELLA project.
  • rules The rules & argumentation module defines roles central to argumentation, and describes the vocabulary for LKIF rules as defined in Deliverable 1.1, chapter 5. The module leaves room for further extension to complex argumentation frameworks (AIF, Carneades).

Core and Extended Ontology

Finally, the twelve modules of the abstract, basic and legal level are integrated in the LKIF-Core ontology module. This module does not provide any additional definitions, but functions as an entry-point for users of the ontology library. The two framework modules are accessible through the LKIF Extended ontology module. This module imports the LKIF Core module.