Asset Oriented Modeling (AOM)

- Keys -

Keys are an optional feature in AOM. If keys must be defined depends on the implementation of the model. Object-oriented implementations, for example, do not require keys, while relational implementations always require keys. XML implementations require keys on some occasions, for example, for cross-references.


Primary keys are used to identify asset instances uniquely within a given domain. 

In the most general form, a primary key is a function of asset key fields f(k1,k2,k3,...) that correlates each asset instance with a unique function value.

A popular, albeit special case is to define a key as a set of key fields {k1,k2,k3,...}. A minimal key is then a set of key fields for which no subset can act as key. 

We allow for two types of key fields:

Preferable are keys that consist of a single, atomic key field. However, this is not always possible.

Composite keys and keys containing delegated key fields must be decorated with a key name to allow their identification. In case of single native key fields the key name defaults to the name of the key field property.

Example: 

keyName {p1,p2,p3,...}


Foreign keys specify the properties of an asset that are used to identify other assets by matching their primary keys.

In AOM, foreign keys are not specified explicitly. Instead, foreign keys can be derived from arc definitions and from the primary keys specified at the target of an arc.

 

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