2.2 Explaining the Classes
The classes need further explanation. This section elaborates on the difference
between classes representing dynamic and static concepts, class constraints, and
clarifies the core concept ‘business activity’.
Firstly, we distinguish between static and dynamic concepts, meaning that dynamic
concepts change more frequent than static ones. Static concepts are shown in blue;
dynamic ones in grey. It implies for instance that a business activity of an actor will
change less frequent than business transactions referring to those business activities,
i.e. the core business activity of an enterprise will probably not change during years.
Second, we will define class constraints. Business activity, value proposition,
business transaction, business activity choreography, event type, and event are the
central concepts. A business activity has choreography of event types. Choreography
of event types is not modelled in this figure; we will discuss this aspect later on. A
business transaction consists of a specific sequence of events that are of a type and
need to be exchanged according to the business transaction choreography. The right
part of the figure shows actors and their support of business activities. An actor
supports a business activity and can define value propositions for those business
activities. These value propositions are published as business services. An actor has a
business process that supports one or more activities and their value propositions. As
a business process supports a business activity, it must also support the related
business transaction protocol and its choreography. The left part of the figure shows
the resource types, which can be the operand and operant resource types. The operant
resources are owned by an actor and can be allocated at a specific time and location to
a business process for the execution of one or more business transactions. These
business transactions control the exchange of the so-called operand resources: goods,
service or rights. It implies that all information exchanged in a business transaction
must be sufficient to exchange the goods, service or right.
Thirdly, the core concept ‘business activity’ needs clarification. We have defined a
business system interoperability model that defines all real world aspects shared by
actors and modelled by business activities provided by those actors, e.g. the
transportation of containers from one place to another, financial risk management, and
insurances against risk. These real world aspects, that either have a physical or a
virtual nature, are considered as business activities that are provided by actors. The
semantics that those business activities have in common are given by the business
system semantic model. A business activity, or in short activity, is able to change the
state of the real world by exchanging a resource (an operand resource defined
according to [4]) according to a particular value proposition. Thus a state transition of
a business system can be induced by executing a business activity. Thus, a business
system interoperability model consists of a state space, modelled by a business system
semantic model, and state transitions on that state space, modelled by business
activities.
State transitions, and thus activities, in general consist of [8]:
• Pre-conditions: a set of conditions (or predicates) that must always be true
before the execution of an activity.
• Post-condition: the actual result of the execution of an activity. The result can
be defined as the state in case an activity is executed successfully.
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