Create custom checks on instance links

Chapter 4 Extending your Models with Profiles

Create custom checks on instance links

The robustness analysis implies some behavioral rules between objects. For example, an actor should always communicate with a boundary object (an interface), entity objects should always communicate with control objects, and so on. To represent these constraints, you are going to define custom checks on the instance links.

Custom checks do not prevent users from performing a syntactically erroneous action, but they allow you to define rules that will be verified by the Check Model function.

You define custom checks with VB scripting.

For more information on VBS syntax, see the Scripting PowerDesigner chapter.

To create custom checks on instance links:

Double-click the arrow beside Robustness Extension in the List of Extended Model Definitions to display the resource editor.

Right-click the Profile category and select Add Metaclass.

The Metaclass Selection dialog box is displayed.

Select InstanceLink in the list of metaclasses displayed in the PdOOM tab and click OK.

The InstanceLink category is displayed under Profile.

Right-click the InstanceLink category and select New→Custom Check.

A new check is created.

Type Incorrect Actor Collaboration in the Name box.

This check verifies if actors are linked to boundary objects. Linking actors to control or entity objects is not allowed in the robustness analysis.

Type "This check ensures that actors only communicate with boundary objects." in the Help Message box.

This text is displayed in the message box that is displayed when the user selects Help in the custom check context menu in the Check Model Parameters dialog box.

Type " The following instance links are incorrect:" in the Output Message box.

Select Error as default severity.

Select the Execute the Check by Default check box.

Click the Check Script tab.

The Check Script tab is the tab where you type the script for the additional check.

Type the following script in the text zone.

Function %Check%(link)
   ' Default return is True
   %Check% = True
   ' The object must be an instance link
   If link is Nothing or not link.IsKindOf(PdOOM.cls_InstanceLink) then
      Exit Function
   End If
   ' Retrieve the link extremities
   Dim src, dst
   Set src = link.ObjectA
   Set dst = link.ObjectB
   ' Source is an Actor
   ' Call CompareObjectKind() global function defined in Global Script pane
   If CompareObjectKind(src, PdOOM.Cls_Actor) Then 
      ' Check if destination is an UML Object with "Boundary" Stereotype
      If not CompareStereotype(dst, PdOOM.Cls_UMLObject, "Boundary") Then
         %Check% = False
      End If
Elsif CompareObjectKind(dst, PdOOM.Cls_Actor) Then 
      ' Check if source is an UML Object with "Boundary" Stereotype
      If not CompareStereotype(src, PdOOM.Cls_UMLObject, "Boundary") Then
         %Check% = False
      End If
   End If
End Function

Click the Global Script tab.

The Global Script tab is the tab where you store functions and static attributes that may be reused among different functions.

Type the following script in the text zone.

' This global function check if an object is of given kind
' or is a shortcut of an object of given kind
Function CompareObjectKind(Obj, Kind)
   ' Default return is false
   CompareObjectKind = False
' Check object
   If Obj is Nothing Then
      Exit Function
   End If
' Shortcut specific case, ask to its target object
   If Obj.IsShortcut() Then
      CompareObjectKind = CompareObjectKind(Obj.TargetObject)
      Exit Function
   End If
If Obj.IsKindOf(Kind) Then
      ' Correct object kind
      CompareObjectKind = True
   End If
End Function
' This global function check if an object is of given kind 
' and compare its stereotype value
Function CompareStereotype(Obj, Kind, Value)
   ' Default return is false
   CompareStereotype = False
   ' Check object
   If Obj is Nothing or not Obj.HasAttribute("Stereotype") Then
      Exit Function
   End If
' Shortcut specific case, ask to its target object
   If Obj.IsShortcut() Then
      CompareStereotype = CompareStereotype(Obj.TargetObject)
      Exit Function
   End If
If Obj.IsKindOf(Kind) Then
      ' Correct object kind
      If Obj.Stereotype = Value Then
         ' Correct Stereotype value
         CompareStereotype = True
      End If   
   End If
End Function

Click Apply.

You are going to repeat steps 4 to 14 and create one check to verify that an instance link is not defined between two boundary objects:

Check definition	Content
Name	Incorrect Boundary to Boundary Link
Help Message	This check ensures that an instance link is not defined between two boundary objects
Output Message	The following links between boundary objects are incorrect:
Default Severity	Error
Execute the check by default	Selected

Type the following check in the Check Script tab:

Function %Check%(link)

   ' Default return is True
   %Check% = True

   ' The object must be an instance link
   If link is Nothing or not 
link.IsKindOf(PdOOM.cls_InstanceLink) then
      Exit Function
   End If
   
   ' Retrieve the link extremities
   Dim src, dst
   Set src = link.ObjectA
   Set dst = link.ObjectB
   
   ' Error if both extremities are 'Boundary' objects
   If CompareStereotype(src, PdOOM.Cls_UMLObject, "Boundary") Then
      If CompareStereotype(dst, PdOOM.Cls_UMLObject, "Boundary") Then
         %Check% = False
      End If
   End If
   
End Function

Repeat steps 4 to 14 and create one check to verify that entity objects are accessed only from control objects:

Check definition	Content
Name	Incorrect Entity Access
Help Message	This check ensures that entity objects are accessed only from control objects
Output Message	The following links are incorrect:
Default Severity	Error
Execute the check by default	Selected

Type the following check in the Check Script tab:

Function %Check%(link)
   ' Default return is True
   %Check% = True
   ' The object must be an instance link
   If link is Nothing or not link.IsKindOf(PdOOM.cls_InstanceLink) then
      Exit Function
   End If
   ' Retrieve the link extremities
   Dim src, dst
   Set src = link.ObjectA
   Set dst = link.ObjectB
   ' Source is and UML Object with "Entity" stereotype?
   ' Call CompareStereotype() global function defined in Global Script pane
   If CompareStereotype(src, PdOOM.Cls_UMLObject, "Entity") Then 
      ' Check if destination is an UML Object with "Control" Stereotype
      If not CompareStereotype(dst, PdOOM.Cls_UMLObject, "Control") Then
         %Check% = False
      End If
   Elsif CompareStereotype(dst, PdOOM.Cls_UMLObject, "Entity") Then 
      ' Check if source is an UML Object with "Control" Stereotype
      If not CompareStereotype(src, PdOOM.Cls_UMLObject, "Control") Then
         %Check% = False
      End If
   End If
End Function

Click Apply.

Click OK in the resource editor.

Select Tools→Check Model to display the Check Model Parameters dialog box.

The custom checks appear in the Instance Link category.

You can test the checks by creating instance links between Customer and Application server for example, and then press F4 to start the check model feature.

For more information on the Check Model feature, see "Checking a Model" in the Models chapter of the Core Features Guide .