Facts forward chaining mechanism

Data-directed expert systems begin with a list of the facts known to be true, and see what conclusions can be drawn from those facts. This type of expert system uses a forward-chaining mechanism. Each rule in the knowledge base is tested to see if all of its IF clauses are contained in the list of known facts. When such a rule is found, the system adds the THEN-clauses from the rule to the list of known facts. All the rules in the knowledge base are scanned repetitively until no new facts can be concluded. An example of using forwardchaining is illustrated by a structure elucidation problem based on an IR spectrum ... 

This reaction has been put forward to explain the observed fact that the number of chain scissions corresponds to the number of carboxyl groups formed in the oxidation of polyethylene. Activation energy of both processes is 140 kj/mol. The mechanism of such an elementary fragmentation reaction remains however uncertain. The reactions of a chain scission are likely to precede the isomerization of original secondary alkyl peroxy radicals. 

A very important EL mechanism—in fact, the most important today in practice—is radiative recombination (by any of several possible processes) of thermal carriers in a forward-biased p-n junction. This process is not important in CPs today because attempts at making stable p-n junctions have essentially failed, probably because, as mentioned above, the dopants are only intercalated between the chains and are therefore mobile in an electric field. 

Facts, rules and quantitative models are the chosen forms of representation for the different areas of knowledge in the field of wool dyeing. But these parts are not independent, they must be tied together, i.e. an inference mechanism is needed. The theoretical concepts of forward and backward chaining in their pure forms turned out to be insufficient to catch fully the expert s knowledge about the connections and interdependencies between the various aspects. Only a careful detailed analysis of the expert s behavior allowed implementation of an adequate inference mechanism, which turned out to be a mixture of several theoretical approaches. 

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