In this paper, we introduce a software system, called DBXML that provides a transformation
utility to connect XML with relational databases. The transformation utility can convert data …

We introduce a restriction of second order logic, SO F, for finite structures. In this restriction
the quantifiers range over relation closed by the equivalence relation Ξ FO. In this …

We initiate in this work the study of a sort of redundancy problem revealed by what we call
redundant relations. Roughly, we define a redundant relation in a database instance (dbi) as …

We review several semantic restrictions to second-order quantification proposed in the
literature. Our focus is on the expressibility and complexity over finite models, or equivalently …

We prove that the existential fragment Σ 1 2, ω of the third order logic TO ω captures the
relational complexity class non deterministic exponential time. As a Corollary we have that …

We introduce a new property for classes of structures (or relational database instances), that
we call bounded FO types. Then we prove that on such classes the expressive power of SOF …

We introduce a restriction of second order logic, SO F, for finite structures. In this restriction
the quantifiers range over relations closed by the equivalence relation≡ FO. In this …

Relational machines (RM) were introduced as abstract machines that compute queries to
relational database instances (dbi's), that are generic (ie, that preserve isomorphisms). As …