Semiotics in Databases

摘要

In database research and practice, syntax is commonly considered a "firstness" property, while semantics is a "secondness" property (in the sense of Peirce); pragmatics is largely neglected. This paper discusses foundations in first-order predicate logic, highlights its usefulness, but also point out its problematic issues. These cover in particular safe expressions in the relational tuple calculus, rigid normalisation emphasising atomicity of attributes, and a large body of knowledge on database constraints. Database theory is still oriented on flat relational structures although systems became object-relational. We first survey the goodliness of classical database constraint theory and then develop an alternative approach to some constraints including (α) the handling of constraint sets instead of homogeneous classes of constraints, (β)visual reasoning on constraints and structures, and (γ) calculi for robust reasoning, in particular for "exceptions" and object-relational reasoning.