L. Byrd. Understanding the control AEow of Prolog programs. In S.-A. T#rnlund, editor, Logic Programming Workshop, 1980.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....by handing the more tricky properties over to Prolog. For the benet of the user, as well as for automation of debugging, it is advantageous to start from an explicit execution model. The model should ideally be simple and complete. One such model happens to be generally known. The 4 port model [2], which is the basis of the standard Prolog debugger, is a complete execution model of Prolog, in the sense of entailing every aspect of Prolog execution of necessity for verication, and therefore all the information one might need. This model maps a query Q to its standard trace T (Q) which is a ....

.... a query Q to its standard trace T (Q) which is a sequence of events of the form Port F(T 1 ; T N ) where Port may be one of fcall, exit, fail, redog, F N are predicates, T i are terms, representing the atomary steps of the Prolog interpreter during the execution of the query Q (as dened in [2,16]) A consequence of such expressive power is also that the amount of information generated by this model be overwhelming, so that its straightforward use as in the standard 4 port debugger is often considered as too low level. One line of research addressing this problem is trace analysis of ....

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Lawrence Byrd. Understanding the control AEow of Prolog programs. In S. A. T#rnlund, editor, Proc. of the Logic Programming Workshop, pages 127138, Debrecen, Hungary, 1980. Also as D. A. I. Research Paper No. 151.

....execution traces. This interpreter can be used both to experiment various trace models to validate them. We have hence a formal framework to specify and prototype trace models. 1 Introduction The basic model for tracing Prolog executions is Byrd s box model, described in a rather informal way in [3]. As detailed in [12] Prolog debugging systems have quite dioeerent interpretations of what Byrd s box model is. It is not always clear whether theses dioeerences come from a misinterpretation of the original model or from a will to improve it. In this article we propose a formal specication of ....

....G 2 ] i 0 ) i) Fig. 2. A continuation semantics that species the Byrd trace 4 Animating the specication This semantics easily maps into any language that is able to manipulate terms. Hence, we can animate this formal specication to see if it corresponds to the informal specication of Byrd [3]. We translate it into Prolog [1,9] because it is a logical programming language that handles terms. We also nd it well suited for meta programming, as demonstrated by Miller [8] In the following, we show how this semantics directly derives into a Prolog program which is a Prolog interpreter ....

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L. Byrd. Understanding the control AEow of Prolog programs. In S.-A. T#rnlund, editor, Logic Programming Workshop, 1980.

....examples can be found in the appendices. 2 Opium s programmability This section brieAEy describes the basic mechanisms of Opium which enable trace abstraction programs to be written. An exhaustive description of Opium can be found in [Ducass#, 1999] Trace format It is based on the box model of [Byrd, 1980]. A trace history, composed of a sequence of trace events, is accessible. A trace event has six slots: Chrono (chronological event number, something like a time stamp) Call (goal invocation number) Depth (depth of the goal in the execution tree) Port (control AEow indication, can be icallj, ....

L. Byrd. (1980). Understanding the control AEow of Prolog programs. In S.-A. T#rnlund, editor, Logic Programming Workshop, Debrecen, Hungary.

....it is a representation of the multi SLD AL tree. The last one is closer to declarative semantics. The execution is abstracted by a forest of proof trees combined with substitution sets. A box oriented trace A box oriented trace gives a sequence of events inspired by those proposed by Byrd in [3]. The meta interpreter is instrumented following the tracing methods of Prolog programs described in [18, 21] The trace format that we choose contains eight ports, including four ports for the non admissible goals. These ports are call, fail, exit, redo, callna, failna, exitna, redona. The na ....

L. Byrd. Understanding the control AEow of Prolog programs. In S.-A. T#rnlund, editor, Logic Programming Workshop, 1980.

....it is a representation of the multi SLD AL tree. The last one is closer to declarative semantics. The execution is abstracted by a forest of proof trees combined with substitution sets. 5. 1 Box oriented trace A box oriented trace gives a sequence of events inspired by those proposed by Byrd in [4]. The meta interpreter is instrumented following the tracing methods of Prolog programs described in [19, 23] The trace format that we choose contains eight ports, including four ports for the non admissible goals. These ports are call, fail, exit, redo, callna, failna, exitna, redona. The na ....

L. Byrd. Understanding the control AEow of Prolog programs. In S.-A. T#rnlund, editor, Logic Programming Workshop, Debrecen, Hungary, 1980.

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L. Byrd. Understanding the control AEow of Prolog programs. In S.-A. T#rnlund, editor, Logic Programming Workshop, 1980.

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