Research in the area of knowledge-based tutoring systems (KBTS) and intelligent tutoring systems (ITS) has great implications for computer applications in education and training. In a KBTS, course material is represented independently of teacher procedures, so that problems and remedial comments can be generated differently for each student. Such a system offers instructions in a manner that is sensitive to the student's strengths, weaknesses, and preferred style of learning; in addition, individualized tutoring can be provided. The objective of the research presented in this paper is to develop a framework upon which effective KBTSs can be built. SQL-TUTOR was developed for the domain of SQL programming. In the design of SQL-TUTOR, an architecture based on a layered curriculum is used to organize the system into components. The course curriculum is represented by a curriculum graph; this architecture has such features as explicit curriculum knowledge representation, multiple teaching sequences, multiple viewpoints of a teaching goal, and overall skill training for students. (AEF)