H. Abramson and V. Dahl, Logic Grammars, Springer-Verlag, 1989.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....free variables. If this is the case, the let needs to be retained. Otherwise, the let can be eliminated. 2.2 Logic grammars and parsing Several approaches have been proposed to enable parsing in logic programs. One can distinguish approaches where logic programming and grammars are amalgamated [47,1,11], or where parsers are explicitly implemented [10,24] A very well known approach belonging to the former class is based on the DCG formalism [47] DCG definite clause grammars) While the body of a pure Horn clause is basically a conjunction of literals, the body of a DCG clause can also ....

V. Dahl and H. Abramson. Logic Grammars. Springer-Verlag, 1989.

.... rule gt [ x; y) True] if match 1 t 1 match 2 t 2 where t 1 = rule id [x] t 2 = rule id [y] rule gt x = According to the general pattern for match above, new function definitions are generated to perform the matching as follows: match 1 ; match 2 : num] bool; match 1 [1] = True; match 1 other = False; match 2 [0] True; match 2 other = False; When rule gt is executed, the first step is to bind the variables (x and y) The second step is to evaluate the first conjunct of the guard (match 1 t 1 ) Then there are two possibilities: False The guard fails and ....

H. Abramson and V. Dahl. Logic Grammars. Springer-Verlag, Berlin, 1989.

....maintained, all programs derivable by the GP system will be executable by the fitness function, and hence their fitness will be derivable. 2. 2 Definite Clause Translation Grammars DCTG s were invented as a means for specifying the syntax and semantics of languages in a convenient, unified fashion [1]. A DCTG has a syntactic component, and possibly multiple semantics components. The syntactic component is equivalent to that used by definite clause grammars [29] and permits the definition of context free languages using a Backus Naur style of syntax. Since DCTG s and DCG s are logic grammars ....

....logical form within the verb and noun phrase portions of the parse tree. 3 SYSTEM DESIGN DCTG GP is a Prolog based genetic programming system [8] It is implemented in Quintus Prolog 3.2 on Silicon graphics IRIX 6. 3 and Windows 98 platforms [35] The DCTG library is authored by Harvey Abramson [1]. The DCTG GP engine uses conventional GP strategies, such as steady state or generational evolution, tournament selection, and local search. Parameters for GP control are outlined in Section 4. The remainder of this section will discuss features particular to the grammatical and logical ....

H. Abramson and V. Dahl. Logic grammars. Springer-Verlag, 1989.

....the operations of movement , insertions and deletions which are not easily performed with functions or lists. Such insertions and deletions occur quite often in morphological analysis. To show how logic grammar rules can be encoded as CLP(S) rules, we give an example in Discontinuous grammar [2]. The rules in these grammars are of the form: S; ff 0 ; skip(X 1 ) ff 1 ; skip(X n ) ff n fi 0 ; skip(X 0 1 ) fi 1 ; skip(X 0 m ) fi m where S is a non terminal and, ffs and fis are strings of terminals and non terminals. fi can also be procedure calls) The Xs denote ....

....skip(X 0 m ) fi m where S is a non terminal and, ffs and fis are strings of terminals and non terminals. fi can also be procedure calls) The Xs denote arbitrary strings which need to be skipped. For example the following rule: DG) Rel marker;skip(G) trace Rel pronoun; skip(G) taken from [2] parses sentences such as the man that John saw laughed , where it considers the noun phrase the man that John saw to be a surface expression of a more explicit statement: the man [John saw the man] where the second occurrence of the man has been moved to the left and subsumed by the ....

H. Abramson and V. Dahl. Logic Grammars. Springer-Verlag, 1989.

.... rule gt [ x; y) True] if match 1 t 1 match 2 t 2 where t 1 = rule id [x] t 2 = rule id [y] rule gt x = According to the general pattern for match i above, new function definitions are generated to perform the matching as follows: match 1 ; match 2 : num] bool; match 1 [1] =True; match 1 other = False; match 2 [0] True; match 2 other = False; When rule gt is executed, the first step is to bind the variables (x and y) The second step is to evaluate the first conjunct of the guard (match 1 t 1 ) Then there are two possibilities: False The guard fails and the ....

H. Abramson and V. Dahl. Logic Grammars. Springer-Verlag, Berlin, 1989.

....DCG from examples; section 3 illustrates this technique with two examples; section 4 describes our procedure for partial execution and its correctness; and section 5 presents the current status of the work and related work. Henceforth we assume the reader has some familiarity with DCGs [18, 1] and unification of typed terms [11] 2. From a CFG to a Higher Order DCG Using Examples We begin with a brief review of the simply typed calculus. Assuming T 0 is a finite set of elementary types (also called primitive types) the set T of types is defined as the smallest superset of T 0 ....

....grammar supports efficient reverse execution of DCGs, because first order unification (rather than higher order matching) is needed. However, in certain cases reverse execution might give incorrect answers, as illustrated by the following example. The grammar s(X Y Y) 0] s(X Y X) [1]. will be expanded to the following clauses: s(X Y Y, 0 T] T) s(X Y X, 1 T] T) When used in parsing mode, this grammar correctly computes X Y Y for [0] and X Y X for [1] However, consider its use in generation mode: s(A B B, Sent, Now, both clauses match: the first clause ....

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H. Abramson and V. Dahl. Logic Grammars. Springer-Verlag, New York, 1989.

....examples, and their convergence suggests that some underlying principle is at work. TAGs, it should be noted, handle some examples beyond the reach of RPDAs [24] 5 The field of logic grammars has also been largely concerned with capturing a number of specific natural language phenomena [1], though reduplication has not been prominent among them. Definite clause grammar (DCG) represents a syntactic variant of the Prolog language, by which a simple grammar translator produces Horn clauses that hide string manipulation concerns from the user and implement a parser by way of standard ....

....served to manage stack manipulations behind the scenes (just as DCGs hide the input string) and to keep the rather byzantine derivations characteristic of indexed grammars from the purview of the derivation tree. SVGs in this form were reminiscent of other logic grammar formalisms such as DG [1, 8]; however, additional machinery was necessary to place palindromes on the same footing as copy languages, as well as to deal with homomorphisms such as base complementarity. Since their first, informal introduction, others have translated SVGs to both a generalized pattern language [14] and to a ....

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H. Abramson and V. Dahl. Logic Grammars. Springer-Verlag, New York, 1989.

.... the affirmative result, and (ii) if the decision procedure terminates and returns the affirmative result, then L 2 WFSX(P ) 3 Grammar and Semantic Composition As is known, a grammar and parser can be used not only to produce syntactic structure, but also to produce semantic representation [1]. For simplicity we will only make use of Definite Clause Grammar (DCG) for both syntactic and semantic analysis. Invisibly to the user, the DCG compiler adds two arguments to each non terminal. The first argument records the input string represented as a list, and the second argument records a ....

....appropriate responses. Depending on the textual database, the DCG grammar may be very big. As meaning representation is a very complicated issue, in this paper we have restricted ourselves to the aspect of exceptions in texts. Other aspects, such as anaphora and coordination, can be treated as in [1]. 7 Concluding Remarks Representing and reasoning about natural language texts is a difficult and complicated task. In this paper we have addressed the semantic issue of exceptions in natural language texts. As natural language is often used by people with common sense, first order logic is not ....

H. Abramson and V. Dahl. Logic Grammars. Springer-Verlag, 1989.

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H. Abramson and V. Dahl, Logic Grammars, Springer-Verlag, 1989.

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Abramson, H., and Dahl, V. Logic Grammars. Springer Verlag, New York, 1989.

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) H. Abramson and V. Dahl. Logic grammars. Springer-Verlag, 1989.

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) H. Abramson and V. Dahl. Logic grammars. Springer-Verlag, 1989.

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H. Abramson, V. Dahl, Logic Grammars. Springer-Verlag, 1989

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