Revisiting Object-Rule Fusion in Query Languages

Object-oriented (O2) and declarative rule-based (RB) paradigms are known and intensively used for decades. There have been many approaches to combine O2 and RB concepts in a uniform framework. However, they either focus on embedding rules into O2 languages, or provide a declarative semantics and proof theory for the O2 machinery. In the current paper we focus on understanding objects as basic building blocks for deductive queries. To achieve the goal of object-rule fusion we use carefully chosen elementary constructs, encompassed in a simple and uniform framework easily extendable and adaptable to many existing RB languages.