Extending LogicWeb via Hereditary Harrop Formulas

Abstract

We propose HHWeb, an extension to LogicWeb with hereditary Harrop formulas. HHWeb extends the LogicWeb of Loke and Davison by allowing goals of the form (∃x₁…∃x_nD)⊃G (or equivalently ∀x₁…∀x_n (D⊃G)) where D is a web page and G is a goal. This goal is intended to be solved by instantiating x₁,…,x_n in D by new names and then solving the resulting goal. The existential quantifications at the head of web pages are particularly flexible in controlling the visibility of names. For example, they can provide scope to functions and constants as well as to predicates. In addition, they have such simple semantics that implementation becomes more efficient. Finally, they provide a client-side interface which is useful for customizing web pages.