The Design and Implementation of TIGUKAT User Languages

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  • Technical report TR93-11. To meet the data management requirements of new complex applications, object management systems are emerging as the most likely candidate. The general acceptance of this new technology depends on the increased functionality it can provide, and one measurement is the power of its query model. Users of these systems must have a declarative language to formulate queries on \"what\" information is required without specifying \"`how\" to efficiently retrieve the information. Therefore, the formal query model should define a declarative calculus that can be used to formulate queries to the objectbase and an equivalent procedural algebra to execute them efficiently. In addition, a user-level language should be provided which has the same expressive power as the formal languages. This thesis presents the new dew Language that was designed and implemented within the framework of the dew project. It is a high level user language which provides declarative access to the underlying objectbase. It is divided into three parts: dew Definition Language (TDL), dew Query Language (TQL), and dew Control Language (TCL). The syntax of this language and the main design choices where influenced by SQL while the semantics is defined in terms of the object calculus. Queries operate on collections and they always evaluate to new collections, thus the results of queries are queryable. Furthermore, queries can be used in the predicates of other queries (i.e., nested queries). Path expressions which allow easy navigation through the schema are supported. Finally, the language is orthogonal to persistence, meaning that all objects are queryable regardless of whether they are persistent or transient. | TRID-ID TR93-11

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    Attribution 3.0 International