VQL, a Visual Query Language for EXPRESS

摘要

Visual Query Language (VQL) is a graphical query language that allows engineers to develop ad hoc queries into EXPRESS data files, e.g. AP203. Traditional visual query generators allow humans to develop simple database queries using schema objects and supplied attribute values. These query interfaces use a method similar to QBE (query by example) to specify which tables are used, attributes selected and values restricted. VQL provides both an interface into EXPRESS structures and the ability to generate complex queries in a complete graphical environment. This paper presents VQL and how it can be used to query complex object structured in EXPRESS data files.