- Forward chaining
Forward chaining is one of the two main methods of reasoning when using
inference rules (inartificial intelligence ). It is referred in philosophical circle asmodus ponens . The opposite of forward chaining isbackward chaining .Forward chaining starts with the available
data and usesinference rule s to extract more data (from an end user for example) until a goal is reached. Aninference engine using forward chaining searches the inference rules until it finds one where the antecedent (If clause) is known to be true. When found it can conclude, or infer, theconsequent (Then clause), resulting in the addition of newinformation to itsdata .Inference engines will iterate through this process until a goal is reached.
For example, suppose that the goal is to conclude the color of a pet named Fritz, given that he croaks and eats flies, and that the
rule base contains the following four rules:# If X croaks and eats flies - Then X is a frog
# If X chirps and sings - Then X is a canary
# If X is a frog - Then X is green
# If X is a canary - Then X is yellowThis
rule base would be searched and the first rule would be selected, because its antecedent (If Fritz croaks and eats flies) matches ourdata . Now the consequents (Then X is a frog) is added to the data. Therule base is again searched and this time the third rule is selected, because its antecedent (If Fritz is a frog) matches our data that was just confirmed. Now the newconsequent (Then Fritz is green) is added to our data. Nothing more can be inferred from this information, but we have now accomplished our goal of determining the color of Fritz.Because the data determines which rules are selected and used, this method is called data-driven, in contrast to goal-driven
backward chaining inference. The forward chaining approach is often employed byexpert system s, such asCLIPS .One of the advantages of forward-chaining over backward-chaining is that the reception of new data can trigger new inferences, which makes the engine better suited to dynamic situations in which conditions are likely to change.
ee also
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Backward chaining
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