Unified Data Language
Date's Unified Data Language
|| Revulsion Strong Influence
|| Negative Mild Influence
SHARE DBMS Language Task Force. "An Evaluation of Three COBOL Data Base Languages -- UDL, SQL, and CODASYL." Proc. SHARE 53 (August 1979). view details
Date, C. J. "An introduction to the unified data language UDL" Proceedings 6th International Conference on VLDB (Montreal, 1980), 15-32. view details
Date, C. J. "Some principles of good language design: with especial reference to the design of database languages" ACM SIGMOD Record 14(3) November 1984 pp1-7 view details
Subieta, Kazimierz "Semantics of query languages for network databases"
Abstract: Semantics determines the meaning of language constructs; hence it says much more than syntax does about implementing the language. The main purpose of this paper is a formal presentation of the meaning of basic language constructs employed in many database languages (sublanguages). Therefore, stylized query languages SSL (Sample Selection Language) and J (Joins) are introduced, wherein most of the typical entries present in other query languages are collected. The semantics of SSL and J are defined by means of the denotational method and explained informally. In SSL and J, four types of expressions are introduced: a selector (denotes a set of addresses), a term (denotes a set of values), a formula (denotes a truth value), and a join (denotes a set of n-tuples of addresses or values). In many cases alternative semantics are given and discussed. In order to obtain more general properties of the proposed languages, a new database access model is introduced, intended to be a tool for the description of the logical access paths to data. In particular, the access paths of the network and relational models can be described. SSL and J expressions may be addressed to both data structures. In the case of the relational model, expressions of J are similar to SQL or QUEL statements. Thus J may be considered a generalization of relational query languages for the network model. Finally, a programming language, based on SSL and J, is outlined, and the issues of SSL and J implementation are considered.
in Transactions on Data Systems 10(3) Sept 1985 view details