Information Technology Reference
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No matter which kind of specialization it is, a duality always covers two dis-
tinct entity sets ; one describing the increments in the resource sets and the other
one the decrements in the resource sets. In the case of a transfer the decrement is
called give and the increment is called take . The decrement of a non-consuming
transformation is denoted as use and the one of a consuming transformation
is denoted as consume . In both kinds of transformation the increment is called
produce .
Figure 3(b) shows an abstract example of a duality model to illustrate the
concepts and their stencils. An entity set is modeled as a partition. Accordingly,
a duality model includes two partitions. The duality shown in the example is a
transfer . It follows that one entity set is a give and the other one is a take .The
kind of entity set is denoted in the upper left corner of the partition.
Accordingtothemetamodel,an entity set covers at least one but up to mul-
tiple economic events .An economic event is considered as a class of phenomena
reflecting changes in scare means [16]. An economic event is specific to the entity
set it belongs to. Following the principles of duality ,all economic events in the
decrement entity set ( give , use , consume ) are counterbalanced by the economic
events in the corresponding increment entity set ( take , produce )ofthesame
duality model.
An economic event is usually executed at a certain point in time. However, in
certain cases the increment/decrement is realized by a series of economic events
each of the same nature. For example, consider that the payment for goods is
split into a number of partial payments. For this purpose we use the concept of an
economic event series , which is defined as a specialization of the economic event
in the meta model. Consequently, the concept of an economic event series may
substitute an economic event . This means, instead of modeling each economic
event of each partial payment, one may model a single economic event series of
partial payments.
An economic event in a give / use / consume entity set decrements resource(s).
Similarly, an economic event in a take / produce entity set increments resource(s).
This relationship between an economic event and an economic resource is de-
scribed by the concept of a stock-flow .A stock-flow models an association
between exactly one economic event and exactly one economic resource .An
economic event will affect most of the time one economic resource only, but it
may affect multiple ones. Thus, an economic event may have one up to many
stock-flows connected. An economic resource usually is affected by many differ-
ent economic events (in different entity sets of different duality models). At a
minimum an economic resource is affected by one economic event -otherwiseit
would not be worth considering the economic resource at all. Consequently, an
economic resource is connected to one up to many stock-flows .
A similar concept to economic event series is defined for economic resources :
the economic resource series .An economic resource series is used if an economic
event affects a number of economic resources of the same kind. For example, on a
high level of abstraction one may define raw material as an economic resource and
an economic event mayaffectanumberof economic resources .Itisimportant
 
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