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	<id>http://termination-portal.org/mediawiki/index.php?action=history&amp;feed=atom&amp;title=TRS_Innermost</id>
	<title>TRS Innermost - Revision history</title>
	<link rel="self" type="application/atom+xml" href="http://termination-portal.org/mediawiki/index.php?action=history&amp;feed=atom&amp;title=TRS_Innermost"/>
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	<updated>2026-04-30T10:19:05Z</updated>
	<subtitle>Revision history for this page on the wiki</subtitle>
	<generator>MediaWiki 1.34.2</generator>
	<entry>
		<id>http://termination-portal.org/mediawiki/index.php?title=TRS_Innermost&amp;diff=2120&amp;oldid=prev</id>
		<title>JCKassing: Added a motivation and link to the ari format (TRS Innermost)</title>
		<link rel="alternate" type="text/html" href="http://termination-portal.org/mediawiki/index.php?title=TRS_Innermost&amp;diff=2120&amp;oldid=prev"/>
		<updated>2026-03-11T09:08:30Z</updated>

		<summary type="html">&lt;p&gt;Added a motivation and link to the ari format (TRS Innermost)&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
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				&lt;tr class=&quot;diff-title&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #222; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #222; text-align: center;&quot;&gt;Revision as of 09:08, 11 March 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l1&quot; &gt;Line 1:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 1:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The TRS Innermost category is concerned with the question &amp;quot;Will every innermost rewrite sequence eventually stop?&amp;quot;.  &lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The TRS Innermost category is concerned with the question &amp;quot;Will every innermost rewrite sequence eventually stop?&amp;quot;.  &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;In other words, does every computation defined by the rewrite rules that only evaluates innermost reducible expressions eventually reach a normal form (a term where no rule applies)?&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;In other words, does every computation defined by the rewrite rules that only evaluates innermost reducible expressions eventually reach a normal form (a term where no rule applies)?&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt; &lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt; &lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;== Category Motivation ==&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt; &lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt; &lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;This category investigates termination under the innermost rewriting strategy, roughly corresponding to a call-by-value evaluation strategy in programming languages,&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot;&gt; &lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;which is one of the most used evaluation strategies.&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;== Syntax &amp;amp; Semantic ==&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;== Syntax &amp;amp; Semantic ==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The syntax and the semantics of term rewrite systems are described [[Term Rewriting | here]].&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The syntax and the semantics of term rewrite systems are described [[Term Rewriting | here]&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;]  and [https://project-coco.uibk.ac.at/ARI/trs.php here&lt;/ins&gt;].&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Formally, a term rewrite system R = {l&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt; &amp;amp;rarr; r&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;,...,l&amp;lt;sub&amp;gt;n&amp;lt;/sub&amp;gt; &amp;amp;rarr; r&amp;lt;sub&amp;gt;n&amp;lt;/sub&amp;gt;} is a finite set of rewrite rules, see [1].&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Formally, a term rewrite system R = {l&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt; &amp;amp;rarr; r&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;,...,l&amp;lt;sub&amp;gt;n&amp;lt;/sub&amp;gt; &amp;amp;rarr; r&amp;lt;sub&amp;gt;n&amp;lt;/sub&amp;gt;} is a finite set of rewrite rules, see [1].&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>JCKassing</name></author>
		
	</entry>
	<entry>
		<id>http://termination-portal.org/mediawiki/index.php?title=TRS_Innermost&amp;diff=2113&amp;oldid=prev</id>
		<title>JCKassing: Added TRS Innermost Category Page</title>
		<link rel="alternate" type="text/html" href="http://termination-portal.org/mediawiki/index.php?title=TRS_Innermost&amp;diff=2113&amp;oldid=prev"/>
		<updated>2026-03-09T17:09:10Z</updated>

		<summary type="html">&lt;p&gt;Added TRS Innermost Category Page&lt;/p&gt;
&lt;p&gt;&lt;b&gt;New page&lt;/b&gt;&lt;/p&gt;&lt;div&gt;The TRS Innermost category is concerned with the question &amp;quot;Will every innermost rewrite sequence eventually stop?&amp;quot;. &lt;br /&gt;
In other words, does every computation defined by the rewrite rules that only evaluates innermost reducible expressions eventually reach a normal form (a term where no rule applies)?&lt;br /&gt;
&lt;br /&gt;
== Syntax &amp;amp; Semantic ==&lt;br /&gt;
&lt;br /&gt;
The syntax and the semantics of term rewrite systems are described [[Term Rewriting | here]].&lt;br /&gt;
&lt;br /&gt;
Formally, a term rewrite system R = {l&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt; &amp;amp;rarr; r&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;,...,l&amp;lt;sub&amp;gt;n&amp;lt;/sub&amp;gt; &amp;amp;rarr; r&amp;lt;sub&amp;gt;n&amp;lt;/sub&amp;gt;} is a finite set of rewrite rules, see [1].&lt;br /&gt;
&lt;br /&gt;
An innermost rewrite step is a rewrite step that rewrites an innermost reducible expression, i.e., no proper subterm is reducible using the rules from R.&lt;br /&gt;
A term rewrite system R is innermost terminating if there exists no infinite rewrite sequence s&amp;lt;sub&amp;gt;0&amp;lt;/sub&amp;gt; &amp;amp;rarr;&amp;lt;sup&amp;gt;i&amp;lt;/sup&amp;gt;&amp;lt;sub&amp;gt;R&amp;lt;/sub&amp;gt; s&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt; &amp;amp;rarr;&amp;lt;sup&amp;gt;i&amp;lt;/sup&amp;gt;&amp;lt;sub&amp;gt;R&amp;lt;/sub&amp;gt; s&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; &amp;amp;rarr;&amp;lt;sup&amp;gt;i&amp;lt;/sup&amp;gt;&amp;lt;sub&amp;gt;R&amp;lt;/sub&amp;gt; ...&lt;br /&gt;
&lt;br /&gt;
== Problem ==&lt;br /&gt;
&lt;br /&gt;
&amp;lt;b&amp;gt;Input&amp;lt;/b&amp;gt;: A term rewrite system R.&lt;br /&gt;
&lt;br /&gt;
&amp;lt;b&amp;gt;Question&amp;lt;/b&amp;gt;: Does R innermost terminate?&lt;br /&gt;
&lt;br /&gt;
&amp;lt;b&amp;gt;Possible Outputs&amp;lt;/b&amp;gt;: &lt;br /&gt;
* &amp;quot;&amp;lt;b&amp;gt;YES&amp;lt;/b&amp;gt;&amp;quot; followed by a termination proof, e.g., a ranking function proving innermost termination of R.&lt;br /&gt;
* &amp;quot;&amp;lt;b&amp;gt;NO&amp;lt;/b&amp;gt;&amp;quot; followed by a nontermination proof, e.g., a loop that indicates an infinite innermost rewrite sequence.&lt;br /&gt;
* &amp;quot;&amp;lt;b&amp;gt;MAYBE&amp;lt;/b&amp;gt;&amp;quot; (indicating that the solver cannot prove termination).&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
== References ==&lt;br /&gt;
&lt;br /&gt;
* [1] Franz Baader and Tobias Nipkow. Term Rewriting and All That. Cambridge University Press, 1998.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
[[Category:Categories]]&lt;/div&gt;</summary>
		<author><name>JCKassing</name></author>
		
	</entry>
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