Abstract data types and extended domain operations in a nested relational algebra.
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文摘
This thesis documents the design and implementation of two enhancements to the Aldat database programming language: abstract data types (ADTs) and extensions to the domain algebra.;Utilizing a nested relational model and an improved procedural abstraction facility, ADTs are declared as computations encapsulating states with their accessor/modifier methods. Objects of an ADT can be instantiated via a single join. As computation calls are embedded into updates and virtual domain actualization, objects are manipulated and accessed solely through the methods exported by the ADT.;The vertical domain algebra empowers Aldat with the capability to combine values along a domain using system defined operators. A mechanism has now been installed to run user defined computations as well. This, coupled with ADTs, opens up the opportunity for Aldat to handle applications such as GIS which require at once the capacity of a traditional DBMS and the computational power of a modern programming language.