1 Introduction. - 1. 1 Model-based and Incremental Knowledge Engineering. - 1. 2 The Knowledge Acquisition and Representation Language KARL. - 1. 3 Some Arguments about Formal and Operational Specification Languages. - 2 Logical-Karl. - 2. 1 Significant Ideas of Other Approaches Used for L-KARL. - 2. 2 Syntax of L-KARL. - 2. 3 Informal Semantics of L-KARL. - 3 Procedural-Karl. - 3. 1 Significant Ideas of Other Approaches Used for P-KARL. - 3. 2 Syntax of P-KARL. - 3. 3 Informal Semantics of P-KARL. - 4 The Karl Model of Expertise. - 4. 1 The Sisyphus Example. - 4. 2 The Domain Layer. - 4. 3 The Inference Layer. - 4. 4 The Task Layer. - 4. 5 The Model of Cooperation. - 5 The Formal Semantics of Karl. - 5. 1 The Formal Semantics of L-KARL. - 5. 2 The Formal Semantics of P-KARL. - 5. 3 The Formal Semantics of a Domain Layer. - 5. 4 The Formal Semantics of an Inference Layer. - 5. 5 The Formal Semantics of a Task Layer. - 6 Conclusion. - 6. 1 Highlights of KARL. - 6. 2 Related Work. - 6. 3 Shortcomings of KARL. - 6. 4 Future Work. - References. Language: English