- To allow for editing of strings in the OCL language.
The OCL editor GUI interface is org.argouml.uml.ui.TabConstraints (shown in the bottom right hand panel - details panel).
org.argouml.ocl.ArgoFacade adapts the tudresden.ocl.gui.OCLEditor for ArgoUML. There are some other helper classes in org.argouml.ocl, with names beginning with OCL but they are used for other purposes. Historically GEF uses OCL as a kind of template language to convert the UML diagrams to pgml(and back again), it doesn't have anything to do with OCL constraints in your UML model.
ArgoFacade is reused by GeneratorJava and TabConstraints.
Currently this subsystem is more or less only Dresden OCL Toolkit and adaptation.
Because of a problem with the interpretation of the UML specification and the OCL specification, the implementation of constraints in ArgoUML is only possible for Classes, Interfaces and Features (Attributes and Operations). See Issue 1805.