The RM Overlay Package

Currently, the only RM overlay settings are for RM attribute visibility, which relates to RM attributes within the context of an archetype. This is described in more detail in the ADL2 specification.

The visibility settings consist of a list of per-RM attribute settings, in the form of instances of the class RM_ATTRIBUTE_VISIBILITY, each keyed by the RM path to the node(s) to which they apply. The path is formed of an object node path within the archetype followed by a path to an RM attribute, which may be on an already-constrained path, or may be a path not already included in the archetype structure. The former part is one of:

The latter part is a path containing no object identifiers (id-codes), of one or mode RM attribute names from the Reference Model. The terminal attribute name will almost always be a single-valued attribute, since the visibility of container attributes will almost always be defined in terms of specifically constrained child objects, i.e. part of the archetyped structure.

Two types of RM visibility can be specified. First, in terms of attribute visibility within modelling tools, using the values show and hide. A non-archetyped RM attribute is by default not visible within an archetype modelling tool visualisation, since it is not part of the archetyped structure. Without visibility settings, the only means of displaying such an attrbute is to display all non-archetyped RM attributes in some generic fashion. Setting the visibility on a particular RM attribute path to show indicates to the tool that this RM attribute should be displayed, along with the archetyped structure - preferably in a visually distinct way. This enables modellers to see specific model attributes that are built into the RM, and do not need to be modelled as archetype objects.

The hide setting is to allow two possibilities:

The visibility setting for an RM attribute with respect to the specialisation lineage (aka inheritance hierarchy) is just the most recent setting, i.e. the setting from the deepest child.

A second visibility setting is an optional alias, which is specified in the form of an at-code whose definition is found in the terminology section of the archetype, in the usual fashion. An alias can be associated with any RM path in the archetype, including non-archetyped RM attributes reachable from the root RM type of the archetype. Definition of an alias enables an RM attribute node to be multi-lingually renamed from its default RM name.