Computer-Aided Materials Selection During Structural Design (1995) / Chapter Skim
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Appendix C: Review of Selected Knowledge-Representation Techniques and Tools
Appendix C: Review of Selected Knowledge-Representation Techniques and Tools
Pages 49-56
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ACTIVE DATA DICTIONARIES Data dictionaries are organized references to data contained in other programs, systems, databases, or collections of files. Whereas databases store and process ordinary data about objects, data dictionaries contain data about data, or metadata.
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Some existing database packages may be able to handle certain types of reasoning about data within the database structure itself, but in most cases the knowledge engineer must either select a different form of knowledge representation to support reasoning requirements or design a new database to handle special problems. New technology for knowl 50 edge discovery in databases shows promise for making the information more useful in the construction of more advanced reasoning systems (Piatetsky-Shapiro and Frawley, 1993; see Active Data Dictionaries.
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Several taxonomies for solid modeling have been proposed, but one way of categorizing most of the existing solid model approaches is to perceive them in three classes: cell-based representations; constructive solid geometry representations; and surface boundary representations. Two distinct approaches in the category of cell-based representations are the cell enumeration technique and the octree approach.
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Frequently, engineering problems require using mathematical relations as symbolic expressions of constraints, however. All constraints are not typically thought of as mathematical relationships and an expert system reasoning about constraints must also admit constraints expressed In a more logic-based formalism (see Constraint-Based Reasonings.
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There are many concepts that have been explored in artificial intelligence and programming language research that are similar to objects and taxonomies, some of which are commercially available in many forms as well as embedded in knowledge-base engineering tools. Abstract data types, frames, schema, relational tables, and semantic networks are the most commonly referred to variants of the technology.
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These characteristics also interact in complex patterns with multiple performance criteria or functional attributes demanded of the artifact being designed. Layout design decisions must simultaneously satisfy global requirements (e.g., usage of space)
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Solids can be described through the surface boundary representation as previously introduced. Boundary solid grammar provides a means of generating complex models of rigid solid objects.
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TRUTH MAINTENANCE Truth maintenance is a knowledge-representation technique that records the justification for information so that the fact is removed if the support for a fact is negated or removed. Truth maintenance techniques have been included in several commercial knowledge-engineering tools.
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