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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<title>Fc_rule Syntax</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link rel="stylesheet" href="../stylesheets/pyke.css" type="text/css" />
</head>
<body>
<table id="page-table">
<thead class="head">
<tr id="header1"><th id="header" colspan="3">
&nbsp;
</th></tr>
<tr id="header2">
<th id="crumb-left"></th>
<th id="crumb-line">
<div id="nav">
<ul>
<li><a href="../index.html">Home</a></li>
<li>&gt;</li>
<li><a href="index.html">KRB Syntax</a></li>
<li>&gt;</li>
<li>Fc_rule</li>
</ul>
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<td id="left-nav">
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<div class="title-nav"><a href="../index.html">Home</a></div><div class="nav-branch">
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<div class="normal-nav"><a href="fc_rule.html">Fc_rule</a></div>
<div class="normal-nav"><a href="bc_rule.html">Bc_rule</a></div>
<div class="normal-nav"><a href="pattern.html">Pattern</a></div>
<div class="normal-nav"><a href="compound_premise.html">Compound Premise</a></div>
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<a name="startcontent" id="startcontent"></a>
<div class="document" id="fc-rule-syntax">
<h1 class="title">Fc_rule Syntax</h1>
<div class="section">
<h2><a id="fc-rule" name="fc-rule">Fc_rule</a></h2>
<p><a class="reference" href="../overview/rules/forward_chaining.html">Forward-chaining</a> <a class="reference" href="../overview/rules/index.html">rules</a> have three parts:</p>
<ol class="arabic simple">
<li>A unique name.</li>
<li>An optional <tt class="docutils literal"><span class="pre">foreach</span></tt> clause.</li>
<li>An <tt class="docutils literal"><span class="pre">assert</span></tt> clause.</li>
</ol>
<pre class="literal-block">
fc_rule ::= IDENTIFIER NL INDENT
[fc_foreach]
fc_assert
DEINDENT
</pre>
<p>The <tt class="docutils literal"><span class="pre">IDENTIFIER</span></tt> uniquely names this <a class="reference" href="../overview/rules/index.html">rule</a> and is used as the corresponding
python function name in the generated &lt;rb_name&gt;_fc.py file.</p>
</div>
<div class="section">
<h2><a id="foreach-clause" name="foreach-clause">Foreach clause</a></h2>
<pre class="literal-block">
fc_foreach ::= 'foreach' NL INDENT
{fc_premise NL}
DEINDENT
fc_premise ::= fact_pattern
| compound_premise
| python_premise
fact_pattern ::= IDENTIFIER '.' IDENTIFIER '(' [{pattern,}] ')'
</pre>
<p>Here are links to the definitions for <a class="reference" href="pattern.html">pattern</a>, <a class="reference" href="compound_premise.html">compound_premise</a> and
<a class="reference" href="python_premise.html">python_premise</a>.</p>
<p>If the <tt class="docutils literal"><span class="pre">foreach</span></tt> clause is <strong>not</strong> used, the <a class="reference" href="../overview/rules/index.html">rule</a> is always fired once.</p>
<p>If the <tt class="docutils literal"><span class="pre">foreach</span></tt> clause <strong>is</strong> used, the <a class="reference" href="../overview/rules/index.html">rule</a> is fired for each
combination of true premises.</p>
</div>
<div class="section">
<h2><a id="assert-clause" name="assert-clause">Assert clause</a></h2>
<pre class="literal-block">
fc_assert ::= 'assert' NL INDENT
{assertion NL}
DEINDENT
assertion ::= fact_pattern
| python_statements
</pre>
<p>Here is the link to the definitions of <a class="reference" href="python_premise.html#python-statements">python_statements</a>.</p>
<p>The <tt class="docutils literal"><span class="pre">assert</span></tt> clause lists new <a class="reference" href="../overview/knowledge_bases/fact_bases.html#facts">facts</a> to assert, and/or python
statements to execute each time the <a class="reference" href="../overview/rules/index.html">rule</a> is fired. Each of these may
include <a class="reference" href="pattern.html#pattern-variable">pattern variables</a> which should also appear in the <tt class="docutils literal"><span class="pre">foreach</span></tt>
clause where they are bound to a value. These values will then be substituted
into the <a class="reference" href="../overview/knowledge_bases/fact_bases.html#facts">facts</a> and python statements.</p>
</div>
</div>
<!-- <div id="return-to-top">
<a href="#">Return to Top</a>
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-->
</div>
</td>
<td id="right-nav">
<div id="right-nav-div">
<h3>More:</h3>
<div class="right-item"><a href="fc_rule.html">Fc_rule Syntax</a><p>The syntax of a forward-chaining rule.</p>
</div>
<div class="right-item"><a href="bc_rule.html">Bc_rule Syntax</a><p>The syntax of a backward-chaining rule.</p>
</div>
<div class="right-item"><a href="pattern.html">Pattern Syntax</a><p>The syntax of a pattern used to match data values.</p>
</div>
<div class="right-item"><a href="compound_premise.html">Compound Premise Syntax</a><p>The syntax of compound premises.</p>
</div>
<div class="right-item"><a href="python_premise.html">Python Premise Syntax</a><p>The syntax of a python premise.</p>
</div>
</div>
</td>
</tr>
</tbody>
<tfoot id="foot">
<tr id="foot2">
<td id="copyright" colspan="3">
Copyright &copy; 2007 Bruce Frederiksen
</td>
</tr>
</tfoot>
</table>
<div id="last-modified">
Page last modified Sat, Jun 07 2008.
</div>
</body>
</html>