1.4. What else is there to know about clausal logic?

The main goal of this chapter has been to introduce the most important concepts in clausal logic, and how it can be used as a reasoning formalism. Needless to say, a subject like this needs a much more extensive and precise discussion than has been attempted here, and many important questions remain. To name a few:

• what are the limits of expressiveness of clausal logic, i.e. what can and what cannot be expressed?

• what are the limits of reasoning with clausal logic, i.e. what can and what cannot be (efficiently) computed?

• how are these two limits related: is it for instance possible to enhance reasoning by limiting expressiveness?

In order to start answering such questions, we need to be more precise in defining what clausal logic is, what expressions in clausal logic mean, and how we can reason with them. That means that we will have to introduce some theory in the next chapter. This theory will not only be useful for a better understanding of Logic Programming, but it will also be the foundation for most of the topics in Part III (Advanced reasoning techniques).

Another aim of Part I of this book is to teach the skill of programming in Prolog. For this, theory alone, however important, will not suffice. Like any programming language, Prolog has a number of built-in procedures and datastructures that you should know about. Furthermore, there are of course numerous programming techniques and tricks of the trade, with which the Prolog programmer should be familiar. These subjects will be discussed in Chapter 3. Together, Chapters 2 and 3 will provide a solid foundation for the rest of the book.