Introduction to Part II

In an ideal world, ontologies would be build in a modular way from the start thus showing the benefits well known from modularization in software engineering. The first part of this book contained an example of how this can be done for databases. Unfortunately, the field of ontology engineering has not yet developed comprehensive models and methods to fully support the development of modular ontologies. There are some approaches aiming at developing principles and formalisms in this direction, but they have not yet found their way into mainstream ontology engineering. As a result, existing ontologies are monolithic models without a clear internal structuring. As the size and complexity of these models can be quite significant (the NCI cancer ontology contains about 27.500 the Gene ontology about 22.000 concepts and the Formal Model of Anatomy (FMA) even 75.000 concepts). A viable way of handling such large models is to chop them up into manageable parts. This part of the book deals with approaches for this task of partitioning large ontologies into smaller parts.