While regular batch processing and reporting remain the main functions of database systems, there is an increasing demand to respond quickly to simple data access requests. The use of nonprocedural query languages greatly simplifies data access by nonprogramming (or ad hoc) users.
In this thesis a strategy for processing query languages in the relational database management system is proposed.
Query processing system is like a compiler in so far as it takes a succession of user requests for information formulated in an applied query languages and translates each one into a series of calls which access an underlying database and transform data from that database into the form the user wishes to see.
But it should be noted that query language is in general very high-level data access language with no storage definition. So another technique called decomposition should be combined into compiler model.
The general procedure of decomposition is to decompose the complex query into a sequence of one-variable queries by alternating between (a) reduction : breaking off components of the query which are joined to it by a single variable, and (b) tuple substitution : substituting for one of the variables a tuple at a time.
For the experimental implementation of query processing system (QPS), PASCAL and COBOL are used as programming languages.
점증하는 interactive query processing에 대한 요구에 응하여 retrieval을 중심으로 이의 해결방법을 모색했다.
query processing system에 입력되는 query language의 일반적인 특성을 검토한 후 compiler 모형을 이용하여 system을 설계 하였다. decomposition 과정이 compiler 모형에 추가되었는데 이에 대한 필요성은 query language가 매우 높은 수준(high-level) 의 language이기 때문에 data mapping 과정이 일반적인 compiler model에 비해 매우 복잡하기 때문이다. 따라서 본 논문에서는 decomposition 과정을 중점적으로 다루어 system의 optimization 이 주로 이 과정에서 이루어지도록 했다.
query processing system의 implementation을 위하여 QPS 라고 이름붙인 system을 만들었는데 기존 query language SEQUEL과 ACCESS method DISAM[9]을 이용하고 programming language로는 PASCAL과 COBOL을 사용하였다.
