Uncertainty in Soft Temporal Constraint Problems:A General Framework and Controllability Algorithms forThe Fuzzy Case

In real-life temporal scenarios, uncertainty and preferences are often essential and coexisting aspects. We present a formalism where quantitative temporal constraints with both preferences and uncertainty can be defined. We show how three classical notions of controllability (that is, strong, weak, and dynamic), which have been developed for uncertain temporal problems, can be generalized to handle preferences as well. After defining this general framework, we focus on problems where preferences follow the fuzzy approach, and with properties that assure tractability. For such problems, we propose algorithms to check the presence of the controllability properties. In particular, we show that in such a setting dealing simultaneously with preferences and uncertainty does not increase the complexity of controllability testing. We also develop a dynamic execution algorithm, of polynomial complexity, that produces temporal plans under uncertainty that are optimal with respect to fuzzy preferences

Combining quantifications for flexible query result ranking

Databases contain data and database systems governing such databases are often intended to allow a user to query these data. On one hand, these data may be subject to imperfections, on the other hand, users may employ imperfect query preference specifications to query such databases. All of these imperfections lead to each query answer being accompanied by a collection of quantifications indicating how well (part of) a group of data complies with (part of) the user's query. A fundamental question is how to present the user with the query answers complying best to his or her query preferences. The work presented in this paper first determines the difficulties to overcome in reaching such presentation. Mainly, a useful presentation needs the ranking of the query answers based on the aforementioned quantifications, but it seems advisable to not combine quantifications with different interpretations. Thus, the work presented in this paper continues to introduce and examine a novel technique to determine a query answer ranking. Finally, a few aspects of this technique, among which its computational efficiency, are discussed

Bipolarity in the querying of temporal databases

A database represents part of reality by containing data representing properties of real objects or concepts. To many real-world concepts or objects, time is an essential aspect and thus it should often be (implicitly) represented by databases, making these temporal databases. However, like other data, the time-related data in such databases may also contain imperfections such as uncertainties. One of the main purposes of a database is to allow the retrieval of information or knowledge deduced from its data, which is often done by querying the database. Because users may have both positive and negative preferences, they may want to query a database in a bipolar way. Moreover, their demands may have some temporal aspects. In this paper, a novel technique is presented, to query a valid-time relation containing uncertain valid-time data in a heterogeneously bipolar way, allowing every elementary query constraint a specific temporal constraint

A note on the temporal sure preference principle and the updating of lower previsions.

This paper reviews the temporal sure preference principle as a basis for inference over time. We reformulate the principle in terms of desirability, and explore its implications for lower previsions. We report some initial results. We also discuss some of the technical difficulties encountered

Rational and Irrational Intentions. An Argument for Externalism

There is plenty of evidence, e.g. in mathematics, in the sciences, and in economics, that rationality is paramount to all other cognitive powers. There is further evidence that intentions are borne and originate in the mind. We therefore might be inclined to conclude that rational intentions are brought about in the mind internally by the best of all cognitive powers. In this case it would be enough to analyse mental representations which are antecedent to decision making in order to find the basic ingredients causing rational or irrational intentions. But there is neither evidence for representations of this sort nor for mental causes of rational intentions. It is true that intending is a mental state or act, but it would, indeed, be false to believe that intentions are produced or brought about internally, i.e., without reference to the external world. Some intentions seem to be irrational although their mental origin is not different from the origin of rational ones. I shall argue that this indifference of origin of rational and irrational intentions is due to the fact that intentions like all volitional attitudes - have external meanings. This implies that the criteria of rationality themselves are external to the mental activities of reasoning and intending. `External' here means that the contents of volitional attitudes are individuated by the objects they are directed to and not by the mental acts or performances of intending themselves. I shall further argue that the indifference of origin of rational and irrational intentions sheds light on the hybrid nature of rationality. For the sake of argument I shall use examples from the theory of choice. The gist of my argument is that intentional states enable us to choose mental acts, speech acts or non-verbal actions without reflecting alternatives beforehand