| <html><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>2.1.9. Containment Constraint</title><link href="style.css" rel="stylesheet" type="text/css"><meta content="DocBook XSL Stylesheets V1.72.0" name="generator"><link rel="start" href="index.html" title="The VIATRA2 Model Transformation Framework"><link rel="up" href="sec_PatternDefinition.html" title="2.1. Pattern Definition"><link rel="prev" href="def_CheckCondition.html" title="2.1.8. Check Condition"><link rel="next" href="sec_LocalPatternlElementDescription.html" title="2.2. Local Pattern Body Elements"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">2.1.9. Containment Constraint</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="def_CheckCondition.html">Prev</a> </td><th align="center" width="60%">2.1. Pattern Definition</th><td align="right" width="20%"> <a accesskey="n" href="sec_LocalPatternlElementDescription.html">Next</a></td></tr></table><hr></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="def_ContainmentConstraint"></a>2.1.9. Containment Constraint</h4></div></div></div><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Tip: Description"><tr><td valign="top" align="center" rowspan="2" width="25"><img alt="[Tip]" src="images/tip.png"></td><th align="left"><a name="def_ContainmentConstraint_Description"></a>Description</th></tr><tr><td valign="top" align="left"><p> | |
| A <span class="strong"><strong>containment constraint</strong></span> | |
| <a name="N108B7" class="indexterm"></a> | |
| is defined in the scope of a variable. It restricts the domain of a | |
| variable with respect to the containment hierarchy of the model space. | |
| </p></td></tr></table></div><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Important: Syntax"><tr><td valign="top" align="center" rowspan="2" width="25"><img alt="[Important]" src="images/important.png"></td><th align="left"><a name="def_ContainmentConstraint_Syntax"></a>Syntax</th></tr><tr><td valign="top" align="left"><pre class="programlisting"> | |
| ContainmentConstraintOptAST ::= $empty | |
| | <span class="token">in</span> <a href="def_ArithmeticTerm.html" title="5.3.1. Arithmetic Term">ArithmeticTermAST</a> | |
| | <span class="token">below</span> <a href="def_ArithmeticTerm.html" title="5.3.1. Arithmetic Term">ArithmeticTermAST</a> | |
| </pre><p> | |
| The <span class="strong"><strong>container</strong></span><a name="N108D6" class="indexterm"></a> in a | |
| <span class="strong"><strong>containment constraint</strong></span> is an | |
| <a href="def_ArithmeticTerm.html" title="5.3.1. Arithmetic Term">arithmetic term</a> which evaluates to an entity. | |
| </p></td></tr></table></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note: Semantics"><tr><td valign="top" align="center" rowspan="2" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left"><a name="def_ContainmentConstraint_Semantics"></a>Semantics</th></tr><tr><td valign="top" align="left"><p> | |
| In case of the <code class="computeroutput">in</code> constraint, the domain of the constrained variable | |
| is restricted to the elements that are directly contained by the | |
| <span class="strong"><strong>container</strong></span>, i.e. the domain contains the children of the | |
| entity defined by the <span class="strong"><strong>container</strong></span>. | |
| </p><p> | |
| In case of the <code class="computeroutput">below</code> constraint the domain of the constrained variable | |
| is restricted to the elements that are directly or indirectly contained by a | |
| <span class="strong"><strong>container</strong></span>, i.e. the domain contains all the descendants | |
| of the <span class="strong"><strong>container</strong></span> (e.g. the children, the | |
| children of the children, etc. in an arbitrary depth). | |
| </p></td></tr></table></div><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Caution: Constraints"><tr><td valign="top" align="center" rowspan="2" width="25"><img alt="[Caution]" src="images/caution.png"></td><th align="left"><a name="def_ContainmentConstraint_Constraints"></a>Constraints</th></tr><tr><td valign="top" align="left"><p> | |
| A containment constraint can be applied only for variables that refer to | |
| entities, but it is a run-time error if the scope of the containment constraint is a relation. | |
| </p></td></tr></table></div><div class="highlights"><a name="def_ContainmentConstraint_UsedBy"></a><p><b>Used By: </b> | |
| <a href="def_ConstrainedVariableList.html" title="5.8.4. Constrained Variable List">constrained variable list</a>, | |
| <a href="def_Entity.html" title="2.2.1. Entity">entity</a> | |
| </p></div><div class="highlights"><a name="def_ContainmentConstraint_SeeAlso"></a><p><b>See Also: </b> | |
| <a href="def_Variable.html" title="5.7.2. Variable">variable</a> | |
| <a href="def_PatternVariable.html" title="2.1.6. Pattern Variable">pattern variable</a> | |
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