GBBopen is a high-performance, open source blackboard-system framework. This tutorial shows you how to get started using GBBopen through a series of exercises that cover GBBopen's concepts and features in a step-by-step sequence. The exercises guide you in creating a simple “random walk” application that simulates taking a sequence of straight-line excursions, each of random length and direction. Although the application is simple, it involves many of GBBopen's features, from very basic to fairly advanced.
GBBopen and Common Lisp
GBBopen is an extension of Common Lisp and uses CLOS (the Common Lisp Object System) and the Metaobject Protocol (MOP) to provide blackboard-specific object capabilities. The blending of GBBopen with Common Lisp transfers all the advantages of a rich, dynamic, reflective, and extensible programming language to blackboard-application developers. Thus, GBBopen's “programming language” includes all of Common Lisp in addition to the blackboard-system extensions documented in the GBBopen Reference manual.
This tutorial does not attempt to teach Common Lisp programming, and an understanding of basic Common Lisp and CLOS concepts is assumed. Although it is possible to read through the tutorial exercises without Common Lisp expertise, a much deeper understanding of GBBopen's potential is gained by understanding how GBBopen and Common Lisp work smoothly together. Two frequently recommended Common Lisp books are Peter Seibel's Practical Common Lisp and Paul Graham's On Lisp. Both books are available on line, as well in traditional book form. A less programmer-oriented introduction to Common Lisp is David Touretzky's Common Lisp: A Gentle Introduction to Symbolic Computation, also available on line.
Ken Pitman's Common Lisp HyperSpec, an easily navigable HTML document derived from the ANSI Common Lisp standard, is the customary programmer's reference for Common Lisp. A down-loadable archive of the HyperSpec is also available, which is very convenient when working without a continuous connection to the Internet. We will show how to make the HyperSpec and the GBBopen Reference HyperDoc directly accessible in your Common Lisp development environment in the Enhancing Your Development Environment exercise.
Using a Common Lisp/GBBopen development environment
The tutorial exercises build on one another, and they are intended to be performed sequentially. The initial exercise involves installing GBBopen and preparing it for use in your environment. This is followed by several exercises where you interact with GBBopen by entering forms into the “Lisp Listener” (also called the read-eval-print-loop or simply the REPL) that is provided by your Common Lisp implementation. As the scope of the random-walk application grows, however, it is important to set up a working environment where your work is done in a file. So, after these initial GBBopen exercises, we will spend an exercise setting up your environment to provide you power-user productivity for the remainder of the tutorial (and for future GBBopen activities). This diversion exercise will be worth your time!
The GBBopen Project