| <html><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>2.2.3. Relationships</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_LocalPatternlElementDescription.html" title="2.2. Local Pattern Body Elements"><link rel="prev" href="def_Relation.html" title="2.2.2. Relation"><link rel="next" href="sec_GraphTransformations.html" title="3. Graph Transformation Rules"></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">2.2.3. Relationships</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="def_Relation.html">Prev</a> </td><th align="center" width="60%">2.2. Local Pattern Body Elements</th><td align="right" width="20%"> <a accesskey="n" href="sec_GraphTransformations.html">Next</a></td></tr></table><hr></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="def_Relationship"></a>2.2.3. Relationships</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_Relationship_Description"></a>Description</th></tr><tr><td valign="top" align="left"><p> | |
| A relationship is a special relation that is model independent and is defined as part of the VPM. It | |
| describes either inheritance (i.e. supertype-subtype) or instantiation (i.e. type-instance) relation. | |
| </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_Relationship_Syntax"></a>Syntax</th></tr><tr><td valign="top" align="left"><pre class="programlisting"> | |
| RelationshipAST ::= InheritanceAST | InstantiationAST | |
| InheritanceAST ::= <span class="token">supertypeOf</span> RelationshipBodyAST | |
| | <span class="token">subtypeOf</span> RelationshipBodyAST | |
| InstantiationAST ::= <span class="token">typeOf</span> RelationshipBodyAST | |
| | <span class="token">instanceOf</span> RelationshipBodyAST | |
| RelationshipBodyAST ::= <span class="token">(</span> <a href="def_PatternVariable.html" title="2.1.6. Pattern Variable">PatternVariableRefAST</a> <span class="token">,</span> <a href="def_PatternVariable.html" title="2.1.6. Pattern Variable">PatternVariableRefAST</a> <span class="token">)</span> | |
| </pre><p> | |
| A <span class="strong"><strong>relationship</strong></span> | |
| <a name="N10B74" class="indexterm"></a> | |
| is either an | |
| <span class="strong"><strong>inheritance</strong></span> | |
| <a name="N10B7D" class="indexterm"></a> | |
| or an | |
| <span class="strong"><strong>instantiation</strong></span> | |
| <a name="N10B88" class="indexterm"></a>. | |
| </p><p> | |
| In each case two model element is referenced by pattern variables references: a | |
| <a href="def_PatternVariable.html" title="2.1.6. Pattern Variable">parent reference</a>, and a | |
| <a href="def_PatternVariable.html" title="2.1.6. Pattern Variable">child reference</a>. | |
| </p><p> | |
| In case of <span class="strong"><strong>inheritance</strong></span> | |
| the parent is the <span class="emphasis"><em>supertype</em></span> | |
| and the child is the <span class="emphasis"><em>subtype</em></span>. | |
| </p><p> | |
| In case of <span class="strong"><strong>instantiation</strong></span> | |
| the parent is the <span class="emphasis"><em>type</em></span> | |
| and the child is the <span class="emphasis"><em>instance</em></span>. | |
| </p><p>In case of both relationships both the parent and the child can be an entity or a relation.</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_Relationship_Semantics"></a>Semantics</th></tr><tr><td valign="top" align="left"><p> | |
| The description of a <span class="strong"><strong>relationship</strong></span> | |
| can appear in the context of a <a href="def_PatternBody.html" title="2.1.2. Pattern Body">pattern body</a>. | |
| It either references an existing relationship if it is used in pattern matching or defines a new | |
| relationship. | |
| </p><p> | |
| In case of <span class="strong"><strong>inheritance</strong></span> | |
| both and refers to the same relationship; only the order of the parameters are different. | |
| </p><p> | |
| In case of <span class="strong"><strong>instantiation</strong></span> | |
| both and refers to the same relationship; only the order of the parameters are different. | |
| </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_Relationship_Constraints"></a>Constraints</th></tr><tr><td valign="top" align="left"><p> | |
| The parent and the child of the relationships must refer to the same type of model element, i.e. either both | |
| refer to entities or both refer to relations. | |
| </p></td></tr></table></div><div class="highlights"><a name="def_Relationship_DefinedIn"></a><p><b>Defined In: </b> | |
| <a href="def_PatternBody.html" title="2.1.2. Pattern Body">local pattern body element</a> | |
| </p></div><div class="highlights"><a name="def_Relationship_UsedBy"></a><p><b>Used By: </b> | |
| <a href="def_CreateRule.html" title="4.4.2. Create Rule">create rule</a>, | |
| <a href="def_DeleteRule.html" title="4.4.3. Delete Rule">delete rule</a> | |
| </p></div><div class="highlights"><a name="def_Relationship_SeeAlso"></a><p><b>See Also: </b> | |
| <a href="def_PatternBody.html" title="2.1.2. Pattern Body">pattern body</a>, | |
| <a href="def_Entity.html" title="2.2.1. Entity">entity</a> | |
| </p></div></div><div class="navfooter"><hr><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="def_Relation.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="sec_LocalPatternlElementDescription.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="sec_GraphTransformations.html">Next</a></td></tr><tr><td valign="top" align="left" width="40%">2.2.2. Relation </td><td align="center" width="20%"><a accesskey="h" href="index.html">Home</a></td><td valign="top" align="right" width="40%"> 3. Graph Transformation Rules</td></tr></table></div></body></html> |