Asset Oriented Modeling (AOM)

- Level 2 -

Level 2 Structures (L2S) are composite structures that consist of multiple assets and/or other Level 2 structures and are demarcated by a labeled box. Top L2Ss usually represent real world objects and are by default considered as first class citizens. Nested L2Ss can add additional structure but are by default not regarded as first class citizens. An L2S can be explicitly marked as first class citizen. First class citizens are drawn with a solid outline, non first class citizens are drawn with a dotted outline.

Within a business scenario, typical L2S are Business Objects and Business Documents:

• Business Objects are assets or groups of assets that play a role in a business process. This requires that we have a rough idea about the process model. 
• Business Documents are assets or groups of assets that are exchanged as messages between Business Objects within the context of a business process. 

Label   The display name for Level 2 Instances. Several names are possible within one label which then act as aliases. Label names are not necessarily unique but belong to the namespace of the identifying asset.  If no name is specified the instances are labeled with the name of the identifying asset. Name formulas may be used as a display label. Annotations The definition of annotations is optional.

Within each L2S one designated asset or nested L2S acts as identifying item. We demarcate each identifying item with a bold outline. A Level 2 Structure is unambiguously identified by its identifying item and belongs to the same namespace. 

The following constraints apply to identifying items:

• Identifying assets must have a key. This will allow us to access Level 2 Instances independently.
• Starting from the identifying item of an L2S we must be able to reach any non-abstract asset belonging to that structure by following arcs in the indicated direction without leaving the Level 2 Structure. This constraint will allow us to interpret each L2S as an aggregation and later allow us to easily implement Level 2 structures as hierarchical objects, for example as XML document types.

L2S and Arc Reversal

To comply to the second constraint may require to reverse the direction of an arc. This transformation of arc reversal represents a change of interpretation: An asset that was originally superior to the identifying asset becomes now a subaltern of the identifying asset. Semantically, this is a reification.

Arc reversal renders any cardinality constraint of that arc invalid. Therefore, the reversed arcs are decorated with "*" to indicate that no cardinality constraint exists for this arc.
In addition, the reversal of an arc renders its role name invalid. It may require the specification of a new role name.

Note: Reverted arcs thus support the definition of structures with hierarchical navigation. Starting at an identifying asset it becomes possible to reach any asset within the same L2S. This sits well with model implementations in object-oriented or XML environments. In relational environments, however, the non-reverted original arc is better suited to the navigation methods found there. Tools therefore may want to carry the characteristics of the original arc with a reverted arc in order to better support relational target. environments.

 

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