Computable queries for relational data bases
نویسندگان
چکیده
منابع مشابه
Computable Queries for Relational Data Bases
The concept of “reasonable” queries on relational data bases is investigated. We provide an abstract characterization of the class of queries which are computable, and define the completeness of a query language as the property of being precisely powerful enough to express the queries in this class. This definition is then compared with other proposals for measuring the power of query languages...
متن کاملRelational Queries Computable in Polynomial Time
We characterize the polynomial time computable queries as those ex pressible in relational calculus plus a least xed point operator and a total ordering on the universe We also show that even without the ordering one application of xed point su ces to express any query expressible with several alternations of xed point and negation This proves that the xed point query hierarchy suggested by Cha...
متن کاملPattern Recognition Using Queries in Relational Tracking Data Bases
Tracking systems provide kinematical information of objects in a scenario. This kinematical information can be combined with additional data to build higher-level-fusion systems that allow the detection of behaviour and threat patterns and thus contribute to situation awareness. The patterns that characterize situations of interest may vary over time and depend on the specific questions to be i...
متن کاملCategorisation of Computable Data-Base Queries
We present an alternative approach to that of Chandra and Harel [CHAN80] and Abiteboul and Vianu [ABIT90] in considering computable database queries, which are mappings from sets of records to sets of records. In particular, we view a computable database query as being realised via a Turing-computable mapping from strings to strings and an encoding, which encodes the input set of records into a...
متن کاملQL: Object-oriented Queries on Relational Data
This paper describes QL, a language for querying complex, potentially recursive data structures. QL compiles to Datalog and runs on a standard relational database, yet it provides familiar-looking object-oriented features such as classes and methods, reinterpreted in logical terms: classes are logical properties describing sets of values, subclassing is implication, and virtual calls are dispat...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Journal of Computer and System Sciences
سال: 1980
ISSN: 0022-0000
DOI: 10.1016/0022-0000(80)90032-x