SYSML11 — 08.Blocks: compartment for property-specific defaultValue should be renamed

As discussed at the OMG TM SysML RTF on Th 13Mar2008. The 'defaultValue' compartment should be renamed 'initialValue' (or perhaps 'initialValues'). The static (class level) default values of a given Block's properties may be overridden on instantiation and initialization of a part Property usage of that Block by the using context. The concept of "initial values" is more consistent with the programmatic practice, and it serves to highlight the difference between the UML2 defaultValue (of a Property within a class) and the (re)initialisation of a SysML value Property on usage of its Block as a part Property within a higher context, by assignment of a property-specific initial value. The label 'initial values' is also consistent with the UML2.1.1 specification description of the role of the defaultValue attribute of 7.2.44 Property: "If there is a default specified for a property, this default is evaluated when an instance of the property is created in the absence of a specific setting for the property or a constraint in the model that requires the property to have a specific value. The evaluated default then becomes the initial value (or values) of the property." Further, the concept of "initial values" emphasises the evolving value state of a system. The "initial value" is then merely a single value slice within a series of values states. Configuration is a special case of "initial value". Example: when a Car leaves a factory it is "initialised" to a luxury, sports, or family configuration. The concept of "initial value" compartment is complemented by the suggestion of a "current values" or simply "values" compartment for recording the value state of an evolving system. (See related issues submitted by Darren Kelly.) This suggestion promotes support of animation of SysML systems, and also encompasses aspects of static configuration consistently.

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