Bernard Szlachta: Bernard Szlachta moved page OCUP2A 03 OCL to OCUP2F 03 OCL

2015-07-08T04:42:32Z

Bernard Szlachta moved page OCUP2A 03 OCL to OCUP2F 03 OCL

New page

[[Category:Private]]
{{Cat|OCUP2}}
==Module 3. Object Constraint Language⌘==
===References⌘===
* OCL Specification Document (Version 2.0 or 2.2; Chapter 7 – All) http://www.omg.org/spec/OCL/
===Object Constraint Language (OCL)⌘===
* OMG Specification
* Object Constraint Language (OCL), a formal language used to describe expressions on UML models
===Why OCL?⌘===
* A UML diagram is typically not refined enough to provide all the relevant aspects of a specification.
* There is a need to describe additional constraints about the objects in the model.
* Such constraints are often described in natural language. Practice has shown that this will always result in ambiguities.
* OCL is a formal language that has been developed to fill this gap.
* OCL expressions do not have side effects (i.e., their evaluation cannot alter the state of the corresponding system).

===Class Diagram Example⌘===
[[File:ClipCapIt-141201-120201.PNG]]
====Context⌘====
Context of an OCL expression within a UML model can be specified through:
* context declaration:
<source lang="objc">
context Company
self.numberOfEmployees > 50
</source>
* in a diagram, with dashed lines to connect it to its contextual element
[[File:ClipCapIt-141201-123904.PNG]]

====Invariants⌘====
* Invariant is OCL expression that must be true for all instances of a classifier at any time.
<source lang="objc">
context Company inv:
self.numberOfEmployees > 50
</source>

====Pre- and Postconditions⌘====
<source lang="objc">
context Typename::operationName(param1 : Type1, ... ): ReturnType
pre : param1 > ...
post: result = ...

context Company inv:
self.numberOfEmployees > 50
</source>

====Invariants⌘====
<source lang="objc">
context Company inv:
self.numberOfEmployees > 50

context Company inv enoughEmployees:
self.numberOfEmployees > 50
</source>

====Invariants⌘====
<source lang="objc">
context Company inv:
self.numberOfEmployees > 50
</source>
====Invariants⌘====
<source lang="objc">
context Company inv:
self.numberOfEmployees > 50
</source>

===Basic OCL types⌘===
[[File:ClipCapIt-141201-122157.PNG]]

OCUP2F 03 OCL - Revision history

Bernard Szlachta: Bernard Szlachta moved page OCUP2A 03 OCL to OCUP2F 03 OCL