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<td class="back"><a id="top"></a><a href="s2.5.a.html" rel="prev">&lt;&lt;&nbsp;&sect;2.5.(a)&nbsp;Using abstract classes for creation</a></td>
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<div class="breadcrumb"><a class="nav" href="s2.html" rel="section">&sect;2&nbsp;Role Binding</a>&nbsp;&gt;&nbsp;<a class="nav" href="s2.5.html" rel="section">&sect;2.5&nbsp;Abstract Roles</a></div>
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<h4 class="subsect">&sect;2.5.(b)&nbsp;<span class="title">Relevant roles</span><a class="img" href="s2.5.b.html" title="PermaLink to (b)&nbsp;Relevant roles"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
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<p>A team must be marked <code>abstract</code> if one of its <strong>relevant roles</strong> is abstract.
<br />
A role is relevant in this sense if
</p>
<ul>
<li>the role class is public <em>or if</em></li>
<li>an explicit <code>new</code> expression
would require to create instances of the role class, <em>or if</em></li>
<li>any of the lifting methods of the enclosing team
would require to create instances of the role class.<br />
A role is irrelevant with respect to lifting
if either of the following holds:
<ul>
<li>It is not bound to a base class, neither directly nor
by an inherited <code>playedBy</code> clause.
</li>
<li>It has a sub-role without a <code>playedBy</code> clause.
</li>
<li>It is bound to an abstract base class, and for all concrete
sub-classes of the base class, a binding to a more specific role class exists.
</li>
</ul>
</li>
</ul>
<p>If neither property, relevance nor irrelevance, can be shown for an abstract role,
a warning is given in case the enclosing team is not abstract.
</p>
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<div class="breadcrumb"><a class="nav" href="s2.html" rel="section">&sect;2&nbsp;Role Binding</a>&nbsp;&gt;&nbsp;<a class="nav" href="s2.5.html" rel="section">&sect;2.5&nbsp;Abstract Roles</a></div>
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OT/J version 1.3 &mdash; last modified: 2010-06-08
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