by Jérôme Euzenat
The World Wide Web has generalised document exchange on a world-wide basis. XML promises to do the same thing for the exchange, manipulation and transformation of structured data. However, if this provides interoperability, it does not help for intelligibility.
Exmo is an INRIA action which studies the communication of formalised knowledge among people mediated by computers. In the communication process, the computer can add value to its medium and memory functions by performing advanced operations such as formatting, filtering, categorising, consistency checking, or generalising. The goal of Exmo is the development of theoretical and software tools for helping the organisation, manipulation, presentation and combination of structured knowledge chunks though allowing communication between people. The knowledge is represented in a formally defined language (which can range from XML - structured, general but without semantics - to knowledge representation languages - structured, semantically characterised, but with a narrow scope of expression).
In order to warrant the suitability and intelligibility of knowledge for the users, this requires to develop an abstract understanding of representations and the transformations applied to them. The research of the Exmo action is focussed in two directions. The transformation topic accounts for the modification of knowledge during the communication while the communication topic accounts for the preservation of intelligibility through transformations.
A transformation is a computational way of generating representations from other representations (not necessarily in the same language). Transformations are used for putting representations together or generating specific representations for a particular need. The goal of the transformation topic is the elaboration of a general theory of transformations based on the properties that transformations satisfy (rather than on the representations or the transformation themselves). Such properties include content or structure preservation, source traceability, or conversely, confidentiality. For instance, it can be useful to define a transformation which delivers a documentation to a customer but which hides some information from the initial source (eg, if a design document includes cost study, it is not advised to communicate this information to sub-contractors). In the context of collaborative work, it is useful to establish the properties of such a filter in order to know where to implement it in the organisation. Conversely, when the elaboration of a representation is a collaborative and continuous process (in the concurrent engineering framework), it is necessary to apply treatments which do not challenge the current stage of development. It is thus relevant to warrant the preservation of content.
One outcome of this work is the capability to decide, given an organisation composing several transformations, and the properties of these transformations, the properties satisfied by the system as a whole. This should be a precious tool for the future information system architects.
More generally, given a set of transformation types and a set of transformation composition operators, one goal is to establish if a property can be decided for an instance of this. Exmo does not aim at helping the implementation of transformations or at inferring properties from implementations. However, some (generally simple) transformation languages implement only one specific interaction type (eg filter) and thus our work is connected to transformation languages in that way.
The communication topic aims at contributing to the proper understanding of the knowledge by people. Formal semantics developed for knowledge representation systems is suited to the use of a system by one user because it is expected that (s)he interprets in a coherent way the terms (identifiers) used. However, when several users communicate, this understanding becomes problematic. Work developed in the field of consensual ontology construction could help to solve the problem of term interpretation. However, other problems are involved. For instance, a user can express knowledge under the form of class hierarchies and first order clauses and then communicate it by using an interoperability language. But if this last language expresses the whole knowledge with clauses (though preserving the semantics of the assertions), the initial user will hardly recognise (and hardly understand) the semantically equivalent result. Hence, when a transformation operates a translation between formal languages, good understanding cannot be ensured by meaning preservation. A semiotic treatment must be applied for ensuring the meaning reconstruction. This treatment comes as a complement to the sheer semantic treatment used in the knowledge representation area.
In order to contribute to the solution of this last problem, we investigate the embedding in XML of the semantics of the language used. Thus, the form can be preserved as much as possible (form is relevant to human understanding) and interoperability is ensured through the availability of the semantics (correct computer treatment mainly depends on semantics).
One step further on this line leads to the consideration, together with structure and semantics, of interpretation policies.
These concepts are applied to technical memories and representation of web document content. However, it will spread to all the aspects of information systems in the future (especially in the context of the generalisation of computer supported collaborative work and the development of the so-called semantic web).
Jérôme Euzenat - INRIA
Tel: +33 4 7661 5366