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<TITLE>The Ciao Prolog System - Programming MYCIN rules</TITLE>
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<H1><A NAME="SEC749" HREF="ciao_toc.html#TOC749">Programming MYCIN rules</A></H1>
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<STRONG>Author(s):</STRONG> Angel Fernandez Pineda.
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<STRONG>Version:</STRONG> 1.10#7 (2006/4/26, 19:22:13 CEST)
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<STRONG>Version of last change:</STRONG> 1.5#59 (2000/2/29, 14:51:54 CET)
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MYCIN databases are declared as Prolog modules containing mycin rules. Those rules are given a
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<EM>certainty factor</EM> (<EM>CF</EM>) which denotates an expert's credibility on that rule:
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<LI>A value of -1 stands for <EM>surely not</EM>.
<LI>A value of 1 stands for <EM>certainly</EM>.
<LI>A value of 0 stands for <EM>I don't know</EM>.
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Intermediate values are allowed.
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Mycin rules work on a different way as Prolog clauses: a rule will never fail (in the Prolog sense), it will return a certainty value instead. As a consequence <STRONG>all</STRONG> mycin rules will be explored during inference, so the order in which rules are written is not significant. For this reason, the usage of the Prolog <EM>cut</EM> (!) is discouraged.
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<LI><A HREF="ciao_188.html#SEC750">Usage and interface (mycin)</A>
<LI><A HREF="ciao_188.html#SEC751">Documentation on new declarations (mycin)</A>
<LI><A HREF="ciao_188.html#SEC752">Known bugs and planned improvements (mycin)</A>
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<H2><A NAME="SEC750" HREF="ciao_toc.html#TOC750">Usage and interface (<CODE>mycin</CODE>)</A></H2>
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<LI><STRONG>Library usage:</STRONG>
In order to declare a mycin database you must include the following declaration as the first one in your file:
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:- mycin(MycinDataBaseName).
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<LI><STRONG>New declarations defined:</STRONG>
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<CODE>export/1</CODE>.
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<H2><A NAME="SEC751" HREF="ciao_toc.html#TOC751">Documentation on new declarations (<CODE>mycin</CODE>)</A></H2>
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<DT><span class="define">DECLARATION:</span> <B>export/1:</B>
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This directive allows a given mycin predicate to be called from Prolog programs. The way in which mycin rules are called departs from Prolog ones. For instance, the followin mycin predicate:
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:- export p/1.
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must be called from Prolog Programs as: <CODE>mycin(p(X),CF)</CODE>, where CF will be binded to the resulting
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certainty factor. Obviously, the variables on <EM>P/1</EM> may be instantiated as you wish. Since the Prolog predicate <EM>mycin/2</EM> may be imported from several mycin databases, it is recommended to fully qualify those predicate goals. For example : <CODE>mydatabase:mycin(p(X),CF)</CODE>.
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<STRONG>Usage:</STRONG> :- <CODE>export(Spec)</CODE>.
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<LI><EM>Description:</EM> <CODE>Spec</CODE> will be a callable mycin predicate.
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<H2><A NAME="SEC752" HREF="ciao_toc.html#TOC752">Known bugs and planned improvements (<CODE>mycin</CODE>)</A></H2>
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Not fully implemented.
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Dynamic mycin predicates not implemented: open question.
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Importation of user-defined mycin predicates requires further design. This includes importation of mycin databases from another mycin database.
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