Between Too Informal and Too Formal

Very few information repositories, especially corporate memories, are formal knowledge bases (KBs) since, despite its benefits, formal and scalable knowledge modelling is inherently a difficult and time-consuming exercise that current generic KB systems (KBSs) still do not guide well. Instead, repositories are most often composed of informal documents that are independently created by people (typically by publishing a Web document or sending an email to a mailing list). This approach is simple but the well-known drawback is that it is then often difficult to retrieve or compare information because (i) the various needed pieces of information are scattered in many documents and expressed in different ways and at often inadequate levels of details, (ii) these pieces of information cannot be automatically organised into a semantic network by any current (or even currently foreseeable) natural language understanding (NLU) technique. The use of cooperatively edited informal documents (as in wikis) helps to reduce the scattering of information but introduces new problems and does not in itself lead to better or sufficient structuring of the information. Structured documents (e.g., documents following an XML schema), databases and application-oriented interfaces enforce some structure but (i) they also often restrict what can be entered even when they provide "free text" entry fields, and (ii) the semantic of the prescribed structure is most often left implicit and is insufficient to be used by KBSs. The occasional use of semantic relations (as in semantic wikis) or of metadata (typically, RDF metadata; especially those automatically generated by tools during document edition), are also insufficient for automated reasoning purposes and hence for "knowledge retrieval", i.e., precision-oriented information retrieval. The use of poorly structured, graphical and overly permissive semi-formal notations such as those used for Topic Maps often lead to information that are more difficult to understand, retrieve and exploit than when regular informal sentences are used. Controlled languages, i.e., semi-formal languages that look like natural languages but have a restricted syntax or a restricted vocabulary, are often seen as good compromises between formal and informal languages but (i) they do not scale (i.e., in the general case, they are not expressive and formal enough or become too complex to use), (ii) they are often more structured, precise, normalised and readable ways to express knowledge (for example, partOf or generalization hierarchies).