A defeasible logic for modelling policy-based intentions and motivational attitudes

Abstract

In this paper we show how defeasible logic could formally account for the non-monotonic properties involved in motivational attitudes like intention and obligation. Usually, normal modal operators are used to represent such attitudes wherein classical logical consequence and the rule of necessitation comes into play, i.e., A/ 2A, that is from A derive 2A. This means that such formalisms are affected by the Logical Omniscience problem. We show that policy-based intentions exhibit nonmonotonic behaviour which could be captured through a non-monotonic system like defeasible logic. To this end we outline a defeasible logic of intention that specifies how modalities can be introduced and manipulated in a non-monotonic setting without giving rise to the problem of logical omniscience. In a similar way we show how to add deontic modalities defeasibly and how to integrate them with other motivational attitudes like beliefs and goals. Finally we show that the basic aspect of the BOID architecture is captured by this extended framework.

Computing Strong and Weak Permissions in Defeasible Logic

“…The strong negation of the above definition gives us the negative proof condition for obligation. Notice that the strong negation of a formula is closely related to the function that simplifies a formula by moving all negations to an inner most position in the resulting formula, and replaces the positive tags with the respective negative tags, and the other way around [6,17]. Definition 9.…”

“…Proof. It straightforwardly follows from the principle of strong negation proposed in [6,17]: indeed, the negative proof tags proposed in this work are defined as the strong negation of the positive ones.…”

One License to Compose Them All

“…l4lod is adopted in our framework as reference vocabulary to specify in a machine-readable format the licensing terms associated to the composite license we automatically generate. Moreover, starting by the observation that not all licensed works are creative works [13], l4lod may be used to specify the deontic components for those licenses outside CC, like for instance ODC licenses, and the Open Government License (OGL) 11 , as through the Open Digital Rights Language (ODRL) vocabulary 12 . The fine grained specification of licensing terms in a machine-readable format is the goal of the ODRL vocabulary, while the aim of l4lod is to describe the composite license at the level of its basic deontic components.…”

Legal contractions

“…Conditions for the negative counterpart are obtained by using the principle of strong negation of [5] and [15]. The tag −∆ X states that it is not possible to obtain a conclusion by only using forward chaining of facts and strict rules.…”