An Access Path Specification Language for restructuring network databases
Donald Swartwout · 1977
The Access Path Specification Language (APSL) is a high-level essentially nonprocedural language for specifying restructuring transformations of network databases. It does so in terms of application-oriented concepts such as access strategies and selection criteria. APSL's approach to restructuring emphasizes description of the source structures from which target data is to be retrieved, rather than the operations needed to convert source constructs to target constructs. The latter approach is used by most current systems to restructure hierarchical data.APSL is based on the Relational Interface Model (RIM) of data, which permits a suitably restricted network database to be viewed simultaneously as a relational database in first normal form. Any restructuring of a RIM database which can be performed by the relational algebra operations Join, Select, Project, and Union can be described in APSL.APSL has been implemented as the restructuring specifications language in the Michigan Data Translator.