The advent of computer aided design and the proliferation of computer aided design tools have been instrumental in furthering the state-of-the­ art in integrated circuitry. Continuing this progress, however, demands an emphasis on creating user-friendly environments that facilitate the interaction between the designer and the CAD tool. The realization of this fact has prompted investigations into the appropriateness for CAD of a number of user-interface technologies. One type of interface that has hitherto not been considered is the natural language interface. It is our contention that natural language interfaces could solve many of the problems posed by the increasing number and sophistication of CAD tools. This thesis represents the first step in a research effort directed towards the eventual development of a natural language interface for the domain of computer aided design. The breadth and complexity of the CAD domain renders the task of developing a natural language interface for the complete domain beyond the scope of a single doctoral thesis. Hence, we have initally focussed on a sub-domain of CAD. Specifically, we have developed a natural language interface, named Cleopatra, for circuit-simulation post-processing. In other words, with Cleopatra a circuit-designer can extract and manipulate, in English, values from the output of a circuit-simulator (currently SPICE) without manually having to go through the output files produced by the simulator.

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1. Introduction.- 1.1. The Pros and Cons of Natural Language Interfaces.- 1.2. Domanial Implications.- 1.3. Cleopatra.- 1.4. Natural Language Processing-Some Preliminaries.- 1.5. An Outline of this Thesis.- 2. Previous Approaches.- 2.1. Syntax-First approaches.- 2.2. Semantic Grammars.- 2.3. Augmented Transition Networks.- 2.4. Case-Frame Parsing.- 3. A New Approach.- 3.1. Flexibility.- 3.1.1. Two Arguments Against Semantic Features.- 3.1.2. The Representation of Constraints in Cleopatra.- 3.2. Parallelism, and Confidence Levels.- 3.2.1. Parallelism.- 3.2.2. Confidence-Levels.- 3.2.3. Updating Confidence-Levels.- 4. The Parsing Process.- 4.1. Lexical Entries.- 4.2. Dictionary Entries.- 4.3. Integration Procedures.- 4.3.1. The integration procedure for nouns.- 4.3.2. The integration procedure for tense.- 5. Filling the Blanks.- 5.1. ''Safe" Attachments.- 5.2. Relative Clauses.- 5.2.1. That Relative Clauses.- 5.2.2. Whiz-Deletion.- 5.2.3. Relative pronoun deletion.- 5.2.4. Headless Relative Clauses.- 5.3. Time-Adverbial Clauses.- 5.4. Conjunctions.- 5.5. Ellipses.- 5.6. Confidence-Levels Revisited.- 5.6.1. Attaching case-frames to verb-frames.- 5.6.2. Concordance of conjuncts.- 5.6.3. Substitutions in Ellipses.- 6. Some Detailed Examples.- 6.1. Example 1.- 6.2. Example 2.- 6.3. Example 3.- 7. Semantic Interpretation.- 7.1. An Outline of the Semantic Interpretation Process.- 7.2. Examples.- 7.2.1. Case-Frame Evaluations.- 7.2.2. The evaluation procedure for .- 7.2.3. The evaluation procedure for .- 8. Issues for Further Research.- 8.1. Extending Cleopatra to Other Domains.- 8.1.1. Linguistic Extensions.- 8.1.2. Portability Considerations.- 8.2. Robustness.- 8.3. Experimental Validation.- 9. Conclusion, and Afterthoughts.- 9.1. Afterthoughts.- Appendix A. A Sample Session with Cleopatra.- A.2. The Session Transcript.- Appendix B. An Exercise in Extension.- References.