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A definite clause grammar (DCG) is a way of expressing grammar, either for natural or formal languages, in a logic programming language such as Prolog. It is closely related to the concept of attribute grammars / affix grammars. DCGs are usually associated with Prolog, but similar languages such as Mercury also include DCGs.
Operationally, Prolog's execution strategy can be thought of as a generalization of function calls in other languages, one difference being that multiple clause heads can match a given call. In that case, the system creates a choice-point, unifies the goal with the clause head of the first alternative, and continues with the goals of that first ...
Aleph searches for clauses in a top-down manner, using the bottom clause constructed in the preceding step to bound the search from below. It searches the refinement graph in a breadth-first manner, with tunable parameters to bound the maximal clause size and proof depth. It scores each clause using one of 13 different evaluation metrics, as ...
The first clause states that a fact holds immediately after an event initiates (or causes) the fact. The second clause is a frame axiom, which states that a fact that holds at a time continues to hold at the next time unless it is terminated by an event that happens at the time. This formulation allows more than one event to occur at the same time:
Quintus Prolog rose to a de facto standard, and significantly influenced the ISO standard for Prolog developed in 1995/6. [1] In addition, while the module system envisaged by the ISO standard deviates from that of Quintus, the Quintus module system is in fact more widely adopted by modern Prolog implementations than that mandated by ISO. [ 1 ]
SWI-Prolog is a free implementation of the programming language Prolog, commonly used for teaching and semantic web applications. It has a rich set of features, libraries for constraint logic programming, multithreading, unit testing, GUI, interfacing to Java, ODBC and others, literate programming, a web server, SGML, RDF, RDFS, developer tools (including an IDE with a GUI debugger and GUI ...
Negation As Failure has been an important feature of logic programming since the earliest days of both Planner and Prolog. In Prolog, it is usually implemented using Prolog's extralogical constructs. More generally, this kind of negation is known as Weak Negation, [1] [2] in contrast with the strong (i.e. explicit, provable) negation.
GNU Prolog (also called gprolog) is a compiler developed by Daniel Diaz with an interactive debugging environment for Prolog available for Unix, Windows, Mac OS X and Linux.It also supports some extensions to Prolog including constraint programming over a finite domain, parsing using definite clause grammars, and an operating system interface.