Temporal Action Logics

The study of frameworks and formalisms for reasoning about action and change [67, 58, 61, 65, 70, 3, 57] has been central to the knowledge representation field almost from the inception of Artificial Intelligence as a general field of research [52, 56]. The phrase “Temporal Action Logics” represents a class of logics for reasoning about action and change that evolved from Sandewall’s book on Features and Fluents [61] and owes much to this ambitious project. There are essentially three major parts to Sandewall’s work. He first developed a narrative-based logical framework for specifying agent behavior in terms of action scenarios. The logical framework is state-based and uses explicit time structures. He then developed a formal framework for assessing the correctness (soundness and completeness) of logics for reasoning about action and change relative to a set of well-defined intended conclusions, where reasoning problems were classified according to their ontological or epistemological characteristics. Finally, he proposed a number of logics defined semantically in terms of definitions of preferential entailment1 and assessed their correctness using his assessment framework. Several of these logics were intended to correspond directly to existing logics of action and change proposed by others at the time, while the rest were new and were intended to characterize broad classes of reasoning problems which subsumed some of the existing approaches. Each of these definitions of preferential entailment were then analyzed using the assessment framework, giving upper and lower bounds in terms of the classes of reasoning problems for which they produced exactly the intended conclusions. Much insight was gained both in terms of advantages and limitations of previously proposed logics of action and change and in how one might go about proposing new logics of action and change in a principled manner with formal assessments included.