They offer an assortment of specialized inference mechanisms to handle tasks like knowledge classification, structuring, etc. Connections between description languages and modal logics have been investigated, but a unifying logical background theory explaining their expressive power and logical characteristics was largely missing. This is the role to be played by hybrid logics. Hybrid languages are modal languages extended with the ability to explicitly refer to elements in the domain of a model. They were first introduced in the mid 1960s, in the field of temporal logic, and were subsequently developed mainly in a purely theoretical environment.
Hybrid languages provide the exact kind of expressive power required to match description languages.
Going in the other direction, description logics provide hybrid logics with extensively tested examples of useful languages, knowledge management lore, and implementations. In this thesis we will draw these two complementary fields together and investigate in detail what each of them has to offer to the other. The particular aim of this thesis is, then, to explore and exploit the connections between description and hybrid logic, their similarities and differences. The main results we will present specifically concern this issue. But we hope to take the first steps in setting and discussing this work in the wider perspective of logic engineering, and provide a small contribution to the general issue of better understanding the rules behind the good design of new formal languages.