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

Lower Bounds and Derandomization

A major open problem in complexity theory is to determine whether randomized complexity classes such as BPP, AM, and MA have any nontrivial derandomization. This thesis investigates the derandomization of two randomized versions of the polynomial hierarchy

The electric Melvin solution in string theory

An electric version of the well-known magnetic Melvin solution of closed string theory is derived. By analogy with the Kaluza-Klein Melvin solution, which is flat space with points identified under a simultaneous rotation and translation in a compact dimension, an orbifold of Minkowski space involving identifications under a Lorentz boost and a translation is introduced. When dimensional reduction to 9 dimensions is performed, the resulting background involves an electric Kaluza-Klein gauge field, giving rise to the electric Melvin interpretation. As was done by other authors for the magnetic Melvin background, a curved generalization of this orbifold is derived using a series of T-duality transformations. The closed string is quantized on the resulting space, and the string spectrum and partition function are calculated.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

On the Complexity of Query Answering under Matching Dependencies for Entity Resolution

Abstract. Matching Dependencies (MDs) are a relatively recent proposal for declarative entity resolution. They are rules that specify, given the similarities satisfied by values in a database, what values should be considered duplicates, and have to be matched. On the basis of a chase-like procedure for MD enforcement, we can obtain clean (duplicate-free) instances; actually possibly several of them. The resolved answers to queries are those that are invariant under the resulting class of resolved instances. In previous work we identified some tractable cases (i.e. for certain classes of queries and MDs) of resolved query answering. In this paper we further investigate the complexity of this problem, identifying some intractable cases. For a special case we obtain a dichotomy complexity result.

Tractable cases of clean query answering under entity resolution via matching dependencies

Abstract. Matching Dependencies (MDs) are a recent proposal for declarative entity resolution. They are rules that specify, given the similarities satisfied by values in a database, what values should be considered duplicates, and have to be matched. On the basis of a chase-like procedure for MD enforcement, we can obtain clean (duplicate-free) instances; possibly several of them. The clean answers to queries (which we call the resolved answers) are invariant under the resulting class of instances. Identifying the clean versions of a given instance is generally an intractable problem. In this paper, we show that for a certain class of MDs, the characterization of the clean instances is straightforward. This is an important result, because it leads to tractable cases of resolved query answering. Further tractable cases are derived by making connections with tractable cases of CQA.

Matching Dependencies: Semantics and Query Answering

Matching dependencies (MDs) are used to declaratively specify the identification (or matching) of certain attribute values in pairs of database tuples when some similarity conditions on other values are satisfied. Their enforcement can be seen as a natural generalization of entity resolution. In what we call the pure case of MD enforcement, an arbitrary value from the underlying data domain can be used for the value in common that is used for a matching. However, the overall number of changes of attribute values is expected to be kept to a minimum. We investigate this case in terms of semantics and the properties of data cleaning through the enforcement of MDs. 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 query answering is investigated. Tractable and intractable cases depending on the MDs are identified and characterized

Tractable vs. intractable cases of query answering under matching dependencies

Matching Dependencies (MDs) are a recent proposal for declarative entity resolution. They are rules that specify, on the basis of similarities satisfied by values in a database, what values should be considered duplicates, and have to be matched. On the basis of a chase-like procedure for MD enforcement, we can obtain clean (duplicate-free), and possibly several, resolved instances. The resolved answers to a query are invariant under the class of resolved instances. Previous work identified classes of queries and sets of MDs for which resolved query answering is tractable, with special emphasis on cyclic sets of MDs. In this work we further investigate the complexity of this problem, identifying intractable cases, and exploring the frontier between tractability and intractability. We concentrate mostly on acyclic sets of MDs. For a special case we obtain a dichotomy result relative to NP-hardness

Matching dependencies with arbitrary attribute values: Semantics, query answering and integrity constraints

Matching dependencies (MDs) are used to declaratively 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 are characterized