7 Comparisons with other approaches

7.1 Logic

Declarative rules are closely related to logic. Indeed, simple rules in SDML are equivalent to logical implications. However, not all deductions that can be logically deduced can be deduced by firing rules. For example, if the consequents of a rule are false, then the antecedents could also be deduced to be false, but this deduction cannot be made by firing the rule.*1 Also some situations that lead to contradictions in SDML may be solved using logic. For example, the rule in figure 8 logically entails that the weather is hot, but this cannot be deduced by firing this rule except by assuming that the weather is not hot! In a logical sense, any set of deductions that is not contradicted by rules and base facts is a possible solution, but SDML only finds solutions that can be derived from the base facts via a sequence of valid rules. Thus, rules are one way of constraining the search space.

An important property of SDML is that any solution that is found is logically consistent, and could have been deduced using logic. It is also important that all solutions for which there is a valid sequence of valid rules can be deduced using SDML. However, formal proofs of these properties are the subject of ongoing research.

SDML has similarities to different kinds of logic. Intuitionistic logic [16], in which predicates are true if they have a constructive proof, is similar because a sequence of rules can be considered a proof. Since SDML has facilities to deal with time, it is similar to temporal logic [12]. SDML's agents can represent and manipulate beliefs about the world and other agents, resembling belief logic [7, 8]. SDML is also similar to default logic [14], because predicates can be assumed until there is evidence that they are not true. The exact logical status of SDML is also part of work in progress.

Efficient Forward Chaining for Declarative Rules in a Multi-Agent Modelling Language - 16 FEB 95

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