Knowledge Representations

The knowledge representation must allow an efficient implementation of all the knowledge that is necessary for the problem area at the same time it must be efficiently usable by the inference strategy. These are often conflicting demands. Finding the right balance is a research subject for AI specialists. Because expert 

In general, a representation method for expert systems should fulfil as well as possible the following criteria  

The two most important representation schemes are the rule-based scheme and the frame-based or object-oriented scheme. 

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Embrey, D. E., Humphreys, P. (1985). Support for Decision-Making and Problem-Solving in Abnormal Conditions in Nuclear Power Plants. In L. B. Methlie R. H. Sprague (Eds.), Knowledge Representation for Decision Support Systems. Amsterdam North Holland. 

Baader F. A formal definition for expressive power of knowledge representation languages. In Proceedings of the 9th European Conference on Artificial Intelligence, ECAI-90, Stockholm, Sweden, 1990, p. 53-58. 

Genesereth MR. Knowledge interchange format. In Proceedings of the 2nd International Conference on the Principles of Knowledge Representation and Reasoning, Allen, 1991, p. 238-249. 

Rather than trying to replace any of the above traditional techniques, this chapter presents the development of complementary frameworks and methodologies, supported by symbolic empirical machine learning algorithms (Kodratoff and Michalski, 1990 Shavlik and Dietterich, 1990 Shapiro and Frawley, 1991). These ideas from machine learning try to overcome some of the weaknesses of the traditional techniques in terms of both (1) the number and type of a priori decisions and assumptions that they require and (2) the knowledge representation formats they choose to express final solutions. 

Hoskins, J. C., and Himmelblau, D. M., Artificial neural network models of knowledge representation in chemical engineering. Comput. Chem. Eng. 12, 881 (1988). 

In these frames all specific columns that are relevant for the reasoning process of the expert system can be described in a structured and comprehensive way. The frame-based and rule-based knowledge representation are both required to represent expertise in a natural way. Therefore, in most expert systems a combination of rule-based and frame-based knowledge representation is used. The rule base together with the factual and descriptive knowledge by means, of e.g., frames constitute the knowledge base of the expert system. 

Implementation tools differ in the facilities they offer. A major selection criterion is the knowledge representation possibilities the tools offer. Another important issue is the access to external programs. This is an important aspect for chemical knowledge bases since many chemical problems involve a large computational aspect that is best solved by an external, algorithmic program. 

Other, more advanced tools offer possibilities for combining different knowledge representations and inferencing strategies. They typically offer rules, combined with frames, different inheritance possibilities. The possibility of object-oriented programming is not always present. The user interface is not standardized and can be user tailored. The interface to standard packages is usually available. 

With the view that a KBS interpreter is a method for mapping from input data in the form of intermediate symbolic state descriptions to labels of interest, four families of approaches are described here, each offering inference mechanisms and related knowledge representations that can be used to solve interpretation problems namely, model-based approaches, digraphs, fault trees, and tables. These methods have been heavily used... 

Before any information can be entered into the knowledge base, decisions must be made about how the rules and data will be represented. The question of knowledge representation is a matter for the knowledge engineer who, from a preliminary discussion with the expert, and meetings with potential... 

Organic chemistry is a unique theater for AI research because over the past 150 years organic chemists have created a powerful graphical knowledge representation scheme. This representation... 

SYNLMA performs a retrosynthetic analysis using a special purpose theorem prover built from LMA components. The compound to be synthesized becomes a theorem to be proved. The reaction rules and starting materials become axioms. The choice of a knowledge representation has been one of our greatest problems. 

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