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| <title>Check</title> |
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| <h1 xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0">Check</h1> |
| <div class="section" title="Check"> |
| <div class="titlepage"> |
| <div> |
| <div> |
| <h2 class="title" style="clear: both"> |
| <a name="Check_language"/> |
| <span class="emphasis"> |
| <em>Check</em> |
| </span> |
| </h2> |
| </div> |
| </div> |
| </div> |
| <div class="section" title="Description of the Check language"> |
| <div class="titlepage"> |
| <div> |
| <div> |
| <h3 class="title"> |
| <a name="Check_language_description"/>Description of the <span class="emphasis"> |
| <em>Check</em> |
| </span> language</h3> |
| </div> |
| </div> |
| </div> |
| <p> |
| <span class="emphasis"> |
| <em>Xpand</em> |
| </span> also provides a language to specify |
| constraints <a name="N10CFF" class="indexterm"/> that the model has to fulfill in order to be correct. |
| This language is very easy to understand and use. Basically, it is built |
| around the expression syntax that has been discussed in detail in the |
| previous section. Constraints specified in the |
| <span class="emphasis"> |
| <em>Check</em> |
| </span> <a name="N10D06" class="indexterm"/> language have to be stored in files with the file |
| extension <code class="filename">.chk</code> <a name="N10D0F" class="indexterm"/> |
| <a name="N10D12" class="indexterm"/>. Furthermore, these files have to be on the Java |
| classpath, of course, in order to be found. Let us look at an example, |
| in order to understand what these constraints look like and what they |
| do:</p> |
| <pre class="programlisting">import data; |
| context Attribute ERROR |
| "Names have to be more than one character long." : |
| name.length > 1;</pre> |
| <p>Now, let us look at the example line by |
| line:</p> |
| <div class="orderedlist"> |
| <ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| <p>First, the metamodel has to be imported.</p> |
| </li> |
| <li class="listitem"> |
| <p>Then, the context is specified for which the constraint |
| applies. In other words, after the <code class="code">context</code> keyword, |
| we put the name of the metaclass that is going to be checked by |
| the constraint. Then, there follows either <code class="code">ERROR</code> or |
| <code class="code">WARNING</code>, These keywords specify what kind of action |
| will be taken in case the constraint fails:</p> |
| <div class="table"> |
| <a name="N10D2C"/> |
| <p class="title"> |
| <b>Table 7. Types of action for <span class="emphasis"> |
| <em>Check</em> |
| </span> |
| constraints</b> |
| </p> |
| <div class="table-contents"> |
| <table summary="Types of action for Check constraints" cellspacing="0" cellpadding="10" style="border-collapse: collapse;border-top: 0.5pt solid ; border-bottom: 0.5pt solid ; border-left: 0.5pt solid ; border-right: 0.5pt solid ; "> |
| <colgroup> |
| <col/> |
| <col/> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td style="border-right: 2 solid #000000; border-bottom: 2 solid #000000; "> |
| <code class="code">WARNING</code> |
| </td> |
| <td style="border-bottom: 2 solid #000000; ">If the constraint fails, the specified message is |
| printed, but the workflow execution is not |
| stopped.</td> |
| </tr> |
| <tr> |
| <td style="border-right: 2 solid #000000; "> |
| <code class="code">ERROR</code> |
| </td> |
| <td style="">If the constraint fails, the specified message is |
| printed and all further processing is stopped.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <p> |
| <br class="table-break"/> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p>Now, the message that is put in case that the constraint |
| fails is specified as a string. It is possible to include the |
| value of attributes or the return value of functions into the |
| message in order to make the message more clear. For example, it |
| would be possible to improve the above example by rewriting it |
| like this:</p> |
| <pre class="programlisting">import data; |
| context Attribute ERROR |
| "Name of '" + name + "too short. Names have to be more than one character long." : |
| name.length > 1;</pre> |
| </li> |
| <li class="listitem"> |
| <p>Finally, there is the condition itself, which is specified |
| by an expression, which has been discussed in detail in the |
| previous section. If this expression is <code class="varname">true</code>, |
| the constraint is fulfilled.</p> |
| </li> |
| </ol> |
| </div> |
| <div class="important" title="Important" style="margin-left: 0.5in; margin-right: 0.5in;"> |
| <h3 class="title">Important</h3> |
| <p>Please always keep in mind that the message that is associated |
| with the constraint is printed, if the condition of the constraint |
| is <code class="varname">false</code>! Thus, if the specified constraint |
| condition is <code class="varname">true</code>, nothing will be printed out |
| and the constraint will be fulfilled.</p> |
| </div> |
| <div class="section" title="Guard Conditions"> |
| <div class="titlepage"> |
| <div> |
| <div> |
| <h4 class="title"> |
| <a name="Guard_conditions"/>Guard Conditions</h4> |
| </div> |
| </div> |
| </div> |
| <p>The <span class="emphasis"> |
| <em>Check</em> |
| </span> language of |
| <span class="emphasis"> |
| <em>Xpand</em> |
| </span> also provides so called <a name="N10D6A" class="indexterm"/>. These conditions allow to apply a check constraint |
| only to model elements that meet certain criteria. Specifying such a |
| guard condition is done by adding an <span class="emphasis"> |
| <em>if</em> |
| </span> clause to |
| the check constraint. The <span class="emphasis"> |
| <em>if</em> |
| </span> clause has to be |
| added after the <span class="emphasis"> |
| <em>context</em> |
| </span> clause as demonstrated by |
| the following example: </p> |
| <pre class="programlisting">import data; |
| context Attribute if name.length > 1 ERROR |
| "Attribute names have to start with an 'a'" : |
| name.startsWith("a");</pre> |
| </div> |
| </div> |
| <div class="section" title="The workflow component CheckComponent"> |
| <div class="titlepage"> |
| <div> |
| <div> |
| <h3 class="title"> |
| <a name="check_checkcomponent"/>The workflow component |
| <span class="emphasis"> |
| <em>CheckComponent</em> |
| </span> |
| </h3> |
| </div> |
| </div> |
| </div> |
| <p>The workflow component |
| <code class="classname">org.eclipse.xtend.check.CheckComponent</code> allows to |
| integrate model validation constraints using the |
| <span class="emphasis"> |
| <em>Check</em> |
| </span> into a modeling workflow using MWE.</p> |
| <p>This component provides the following configuration |
| properties:</p> |
| <div class="table"> |
| <a name="properties_checkcomponent"/> |
| <p class="title"> |
| <b>Table 8. Properties</b> |
| </p> |
| <div class="table-contents"> |
| <table summary="Properties" cellspacing="0" cellpadding="10" style="border-collapse: collapse;border-top: 0.5pt solid ; border-bottom: 0.5pt solid ; border-left: 0.5pt solid ; border-right: 0.5pt solid ; "> |
| <colgroup> |
| <col align="left"/> |
| <col align="left"/> |
| </colgroup> |
| <thead> |
| <tr> |
| <th style="border-right: 2 solid #000000; border-bottom: 2 solid #000000; " align="left">Name of property</th> |
| <th style="border-bottom: 2 solid #000000; " align="left">Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td style="border-right: 2 solid #000000; border-bottom: 2 solid #000000; " align="left"> |
| <code class="varname">checkFile</code> |
| </td> |
| <td style="border-bottom: 2 solid #000000; " align="left">This property allows to add files containing constraints |
| written in the <span class="emphasis"> |
| <em>Check</em> |
| </span> language to the |
| validation component.</td> |
| </tr> |
| <tr> |
| <td style="border-right: 2 solid #000000; border-bottom: 2 solid #000000; " align="left"> |
| <code class="varname">emfAllChildrenSlot</code> |
| </td> |
| <td style="border-bottom: 2 solid #000000; " align="left">Name of a workflow slot that contains an EMF object, |
| which has to be validated including all child elements that it |
| contains. <span class="emphasis"> |
| <em>This property only works in conjunction with |
| EMF based models.</em> |
| </span> |
| </td> |
| </tr> |
| <tr> |
| <td style="border-right: 2 solid #000000; border-bottom: 2 solid #000000; " align="left"> |
| <code class="varname">expression</code> |
| </td> |
| <td style="border-bottom: 2 solid #000000; " align="left">This property allows to set a check expression for the |
| validation component. <span class="strong"> |
| <strong>This property only |
| works in conjunction with non-EMF based |
| models.</strong> |
| </span> |
| </td> |
| </tr> |
| <tr> |
| <td style="border-right: 2 solid #000000; border-bottom: 2 solid #000000; " align="left"> |
| <code class="varname">abortOnError</code> |
| </td> |
| <td style="border-bottom: 2 solid #000000; " align="left">This boolean property determines if the workflow will be |
| aborted or not if one of the validation constraints |
| fails.</td> |
| </tr> |
| <tr> |
| <td style="border-right: 2 solid #000000; " align="left"> |
| <code class="varname">warnIfNothingChecked</code> |
| </td> |
| <td style="" align="left">If this boolean property will be set to |
| <span class="emphasis"> |
| <em>true</em> |
| </span>, a warning will be generated if there |
| were no validation checks. Otherwise, no warning will be |
| issued.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <br class="table-break"/> |
| </div> |
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