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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>Asserting New Facts</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link rel="stylesheet" href="../stylesheets/pyke.css" type="text/css" />
</head>
<body>
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<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">Using Pyke</a></li>
<li>&gt;</li>
<li>Asserting Facts</li>
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<div class="document" id="asserting-new-facts">
<h1 class="title">Asserting New Facts</h1>
<!-- this code is hidden and will set __file__ to the doc/examples directory.
>>> import os
>>> __file__ = \
... os.path.join(os.path.dirname(os.path.dirname(os.getcwd())),
... 'examples')
>>> from pyke import knowledge_engine
>>> my_engine = knowledge_engine.engine(__file__) -->
<dl class="docutils">
<dt><em>some_engine</em>.add_universal_fact(kb_name, fact_name, arguments)</dt>
<dd><p class="first">The <tt class="docutils literal"><span class="pre">add_universal_fact</span></tt> function is called once per <a class="reference external" href="../knowledge_bases/fact_bases.html#facts">fact</a>. These
<a class="reference external" href="../knowledge_bases/fact_bases.html#facts">facts</a> are never deleted and apply to all <em>cases</em>.</p>
<p>Alternatively, you can place universal facts in a <a class="reference external" href="../pyke_syntax/kfb_syntax.html">.kfb file</a> so that
they are loaded automatically.</p>
<pre class="doctest-block">
&gt;&gt;&gt; my_engine.add_universal_fact('family', 'son_of', ('bruce', 'thomas'))
</pre>
<p>Multiple facts with the same name are allowed.</p>
<pre class="doctest-block">
&gt;&gt;&gt; my_engine.add_universal_fact('family', 'son_of', ('david', 'bruce'))
</pre>
<p>But duplicate facts (with the same arguments) are silently ignored.</p>
<pre class="doctest-block">
&gt;&gt;&gt; my_engine.add_universal_fact('family', 'son_of', ('david', 'bruce'))
&gt;&gt;&gt; my_engine.get_kb('family').dump_universal_facts()
son_of('bruce', 'thomas')
son_of('david', 'bruce')
</pre>
<p class="last">These facts are accessed as <tt class="docutils literal"><span class="pre">kb_name.fact_name(arguments)</span></tt> within the
<a class="reference external" href="../pyke_syntax/krb_syntax/index.html">.krb files</a>.</p>
</dd>
<dt><em>some_engine</em>.assert_(kb_name, fact_name, arguments)</dt>
<dd><p class="first">Call <tt class="docutils literal"><span class="pre">assert_</span></tt> for each starting <a class="reference external" href="../knowledge_bases/fact_bases.html#facts">fact</a> for this case. Like universal
facts, you may have multiple facts with the same name so long as they
have different arguments.</p>
<pre class="doctest-block">
&gt;&gt;&gt; my_engine.assert_('family', 'son_of', ('michael', 'bruce'))
&gt;&gt;&gt; my_engine.assert_('family', 'son_of', ('fred', 'thomas'))
&gt;&gt;&gt; my_engine.assert_('family', 'son_of', ('fred', 'thomas'))
</pre>
<p>Duplicates with universal facts are also ignored.</p>
<pre class="doctest-block">
&gt;&gt;&gt; my_engine.assert_('family', 'son_of', ('bruce', 'thomas'))
&gt;&gt;&gt; my_engine.get_kb('family').dump_specific_facts()
son_of('michael', 'bruce')
son_of('fred', 'thomas')
&gt;&gt;&gt; my_engine.get_kb('family').dump_universal_facts()
son_of('bruce', 'thomas')
son_of('david', 'bruce')
</pre>
<p>There is no difference within the <a class="reference external" href="../pyke_syntax/krb_syntax/index.html">.krb files</a> of how universal facts
verses case specific facts are used. The only difference between the two
types of facts is that the case specific facts are deleted when a <tt class="docutils literal"><span class="pre">reset</span></tt>
is done.</p>
<pre class="last doctest-block">
&gt;&gt;&gt; my_engine.reset()
&gt;&gt;&gt; my_engine.get_kb('family').dump_specific_facts()
&gt;&gt;&gt; my_engine.get_kb('family').dump_universal_facts()
son_of('bruce', 'thomas')
son_of('david', 'bruce')
</pre>
</dd>
</dl>
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<h3>More:</h3>
<div class="right-item"><a href="creating_engine.html">Creating an Inference Engine Object</a><p>How to create a Pyke <em>inference engine</em> object.</p>
</div>
<div class="right-item"><a href="adding_facts.html">Asserting New Facts</a><p>How to dynamically assert new <em>facts</em> from your Python program.</p>
</div>
<div class="right-item"><a href="proving_goals.html">Proving Goals</a><p>Using Pyke's API to prove goals from your Python program.</p>
</div>
<div class="right-item"><a href="other_functions.html">Other Functions</a><p>Other miscellaneous functions available that you might be interested
in, such as tracing rules and smart error tracebacks that show lines
from your .krb files.</p>
</div>
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Copyright &copy; 2007-2009 Bruce Frederiksen
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Page last modified
Mon, Mar 08 2010.
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