Example: Creating Custom Checks on Instance Links

We will now create three custom checks on the instance links that will connect the various robustness objects. These checks, which are written in VB, do not prevent users from creating diagrams not supported by the robustness methodology, but define rules that will be verified when you check your model.

1. Right-click the Profile category, select Add Metaclasses to open the Metaclass Selection dialog, select InstanceLink on the PdOOM tab and click OK to add it to the extension file.
2. Right-click the InstanceLink category and select New > Custom Check to create a check under the metaclass.
3. Enter the following values for the properties on the General tab:

   Field	Value
   Name	Incorrect Actor Collaboration
   Comment	This check verifies if actors are linked to boundary objects. Linking actors to control or entity objects is not allowed in the robustness analysis.
   Help message	This check ensures that actors only communicate with boundary objects.
   Output message	The following instance links are incorrect:
   Default severity	Error
   Execute the check by default	[selected]

4. Select the Check Script tab and enter the following script in the text field:

   Function %Check%(link)
      ' Default return is True
      %Check% = True
      
      ' The object must be an instance link
      If link is Nothing then
         Exit Function
      End if
      If 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      
      ElseIf 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

   Note: For more information on VBS, see Scripting PowerDesigner.
5. Select the Global Script tab (where you store functions and static attributes that may be reused among different functions) and enter the following script in the text field:

   ' 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 it's target object
      If Obj.IsShortcut() Then
         CompareObjectKind = CompareObjectKind(Obj.TargetObject, Kind)
         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 it's stereotype value
   Function CompareStereotype(Obj, Kind, Value)
      ' Default return is false
      CompareStereotype = False
      
      ' Check object
      If Obj is Nothing then
         Exit Function
      End If   
      if (not Obj.IsShortcut() and not Obj.HasAttribute("Stereotype")) Then
         Exit Function
      End If
      ' Shortcut specific case, ask to it's target object
      If Obj.IsShortcut() Then
         CompareStereotype = CompareStereotype(Obj.TargetObject, Kind, Value)
         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
   
   ' This global function copy the standard attribute 
   ' from source to target
   Function Copy (src, trgt)
      trgt.name = src.name
      trgt.code  = src.code
      trgt.comment = src.comment
      trgt.description = src.description
      trgt.annotation = src.annotation
      Dim b, d
      for each b in src.AttachedRules
         trgt.AttachedRules.insert -1,b
      next
      for each d in src.RelatedDiagrams
         trgt.RelatedDiagrams.insert -1,d
      next
      output " "
      output trgt.Classname & " " & trgt.name & " has been created."
      output " "
   End Function

6. Repeat these steps to create a second check by entering the following values:

   Field	Value
   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]
   Check Script	Function %Check%(link) ' Default return is True %Check% = True ' The object must be an instance link If link is Nothing then Exit Function End if If 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

7. Repeat these steps to create a third check by entering the following values:

   Field	Value
   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]
   Check Script	Function %Check%(link) ' Default return is True %Check% = True ' The object must be an instance link If link is Nothing then Exit Function End if If 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 ElseIf 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

   
   
   
8. Click Apply to save your changes before continuing.
   For detailed information about creating custom checks, see Custom Checks (Profile).