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BS ISO/IEC 13211-1:1995
Information technology. Programming languages. Prolog. General core (British Standard)
Designed to promote the applicability and portability of Prolog text and data among a variety of data processing systems. Specifies: the representation of Prolog text; the syntax and constraints of the Prolog language; the semantic rules for interpreting Prolog text; the representation of input data to be processed by Prolog; the representation of output produced by Prolog and the restrictions and limits imposed on a conforming Prolog processor.
British Standards Institution [bsi]