In order to enable the database programmer to reason about relations over strings of arbitrary length we introduce alignment logic, a modal extension of relational calculus. In addition to relations, a state in the model consists of a two-dimensional ...

We study classes of infinite but finitely representable databases based on constraints, motivated by new database applications such as geographical databases. The mathematical framework is based on classical decidable first-order theories. We ...

A general model for spatial databases is considered, which extends the relational model by allowing as tuple components not only atomic values but also geometrical figures. The model, which is inspired by the work of Kanellakis, Kuper and Revesz on ...

We study the expressive power and complexity of disjunctive datalog, i.e., datalog with disjunctive rule heads, under three different semantics: the minimal model semantics, the perfect models semantics, and the stable model semantics. We show that the ...

We present a typed polymorphic calculus that supports a general mechanism for view definition and object sharing among classes. In this calculus, a class can contain inclusion specifications of objects from other classes. Each such specification ...

Current object-oriented data models lack several important features that would allow one to express relevant knowledge about the classes of schema. In particular, there is no data model supporting simultaneously the inverse of the functions represented ...

We study a mechanism that supports the migration of objects from one class of an OODB to another, thereby enabling us to model the same object playing different roles throughout its lifetime. Object migration may introduce typing conflicts due to the ...

We present a functional framework for database query languages, which is analogous to the conventional logical framework of first-order and fixpoint formulas over finite structures. We use atomic constants of order 0, equality among these constants, ...

Traditionally, computational complexity has considered only static problems. Classical Complexity Classes such as NC, P, NP, and PSPACE are defined in terms of the complexity of checking—upon presentation of an entire input—whether the input satisfies a ...

The Abiteboul and Beeri algebra for complex objects can express a query whose meaning is transitive closure, but the algorithm is naturally associated to this query needs exponential space. We show that any other query in the algebra which expresses ...

The problem of determining whether, for every extensional database, a given predicate in a given program has a finite number of derivations is called the universal finiteness problem. The problem of determining whether a given predicate in a given ...

We present a language for querying list-based complex objects. The language is shown to express precisely the polynomial-time generic list-object functions. The iteration mechanism of the language is based on a new approach wherein, in addition to the ...

We show that a form of divide and conquer recursion on sets together with the relational algebra expresses exactly the queries over ordered relational databases which are NC-computable. At a finer level, we relate k nested uses of recursion exactly to ...

We provide new techniques for the analysis of the expressive power of query languages for nested collections. These languages may use set or bag semantics and may be further complicated by the presence of aggregate functions. We exhibit certain classes ...

In the presence of semantic information, serializability is too strong a correctness criterion and unnecessarily restricts concurrency. We use the semantic information of a transaction to provide different atomicity views of the transaction to other ...

Serializability is the standard correctness criterion for concurrency control. To ensure correctness in the presence of failures, recoverability is also imposed. Pragmatic considerations result in further constraints, for instance, the existing log-...

It has been demonstrated that simulated annealing provides high-quality results for the data clustering problem. However, existing simulated annealing schemes are memory-based algorithms; they are not suited for solving large problems such as data ...

In a previous paper, we have proved tight complexity bounds for the equivalence of recursive and nonrecursive Datalog programs: triply exponential time in general and doubly-exponential space for linear programs. In this paper, we show that under ...