In explaining functional dependency to students, I have noticed in texts a mixture of two types of elements: intensional (or psychological or meaning) and extensional (patterns of repetition in the data). In this chapter I examine whether it is possible to consider functional dependency, in particular, in second and third normal forms, solely on an extensional basis. The Microsoft Access Analyz...

Extensional (table) constraints are an important tool for attacking combinatorial problems with constraint programming. Recently there has been renewed interest in fast propagation algorithms for these constraints. We describe the use of two alternative data structures for maintaining generalised arc consistency on extensional constraints. The first, the Next-Difference list, is novel and has b...

Observational Type Theory (OTT) combines beneficial aspects of Intensional and Extensional Type Theory (ITT/ETT). It separates definitional equality, decidable as in ITT, and a substitutive propositional equality, capturing extensional equality of functions, as in ETT. Moreover, canonicity holds: any closed term is definitionally reducible to a canonical value. Building on previous work by each...

The following work reports the design, numerical, analytical and simulation characterization of an Aluminum Nitride MEMS resonator. The paper offers a comparison of rectangular plate MEMS resonator (length extensional and width extensional mode shapes) and ring shape MEMS resonator. It also demonstrates the contour Eigen modes of resonators and their equivalent electric circuit model (BVD). Fur...

We relate two sequential models of PCF: the sequential algorithm model due to Berry and Curien and the strongly stable model due to Bucciarelli and the author. More precisely, we show that all the morphisms araising in the strongly stable model of PCF are sequential in the sense that they are the \extensional projections" of some sequential algorithms. We deene a model of PCF where morphisms ar...

Designing rewriting systems that respect functional extensionality for call-by-name languages with effects turns out to be surprisingly challenging. Simply interpreting extensional laws like η as reduction rules easily breaks confluence. We explore these issues in the setting of a sequent calculus. Building on an insight that appears in different aspects of the theory of call-by-name functional...

We set up a framework for the study of extensionality in the context of higher-order logic programming. For simply typed logic programs we propose a novel declarative semantics, consisting of a model class with a semicomputable initial model, and a notion of extensionality. We show that the initial model of a simply typed logic program, in case the program is extensional, collapses into a simpl...