Matching Dependencies with Arbitrary Attribute Values: Semantics, Query Answering and Integrity Constraints

Matching dependencies (MDs) were introduced to specify the identification or matching of certain attribute values in pairs of database tuples when some similarity conditions are satisfied. Their enforcement can be seen as a natural generalization of entity resolution. In what we call the "pure case" of MDs, any value from the underlying data domain can be used for the value in common that does the matching. We investigate the semantics and properties of data cleaning through the enforcement of matching dependencies for the pure case. We characterize the intended clean instances and also the "clean answers" to queries as those that are invariant under the cleaning process. The complexity of computing clean instances and clean answers to queries is investigated. Tractable and intractable cases depending on the MDs and queries are identified. Finally, we establish connections with database "repairs" under integrity constraints.Comment: 13 pages, double column, 2 figure

A314/SEF/TAI/DS/P/001/b1 Videotelephony Fitness-for-Purpose Requirements ETSI ETR 250

Active databases are usually centered around the notion of Event-Condition-Action (ECA) rules. An ECA rule’s action is executed upon detection of an event whenever the rule’s condition is true. Events are traditionally described using an event algebra. Virtually every proposed active database management system (ADBMS) brings about a different event algebra. This makes it very difficult to analyze these proposals in a uniform way by spelling out what they may have in common, or how they may differ. Typically, logic might act as a framework for dealing with these issues. This paper treats events as (somewhat constrained) formulas of the situation calculus, a (second order) logic for reasoning about actions in general, and database updates and transactions in particular. We provide a framework for devising the semantics of complex events in this logic. Such semantics, formulated as theories of a special kind, are used for reasoning about the occurrence and consumption modes, which are an important dimension of events.

Towards a general theory of advanced transaction models in the situation calculus

We propose a theory for describing, reasoning about, and simulating transaction models that relax some of the ACID properties of classical transactions. Such models have been proposed for database applications involving long-lived, endless, and cooperative activities. Our approach appeals to non-Markovian theories, in which one may refer to past states other than the previous one. We illustrateour framework by formalizing closed nested transactions (CNTs). We first formulate CNTs as a suitable non-Markovian theory. Then we define a legal database log as one whose actions are all possible and in which all the  ¢¡¤£¥£§¦© ¨ ¡������������ and actions must occur whenever they are possible. After that, we show that the relaxed ACID constraints are properties of legal logs and logical consequences of the theory corresponding to the CNTs. Finally, we use such a specification as a background theory for transaction programs written in the language GOLOG.