TR 62055-21 IEC:2005(E) – 17 –
An arrow represents a process, which is an interactive relationship between two function
objects. For example: process (6) manifests as the relationship between the Contract function
and the Distribution function and is named Connection_Authorization.
The dot on the arrow represents the causal starting point of the process and the head
represents the conclusive end point of the process. For example: process (3) is started by the
Contract function and results in the establishment of a customer account within the
Accounting function, which is the conclusive end of process (3).
A system state box represents a particular condition that a function enters into when a given
event in the system causes it to do so. Such a condition is then a pre-requisite before other
related events may be initiated. For example: process (1) and (2) are both required to
instantiate a state in the Contract function, from which processes (3), (4), (5) and (6) may be
started.
A begin state circle simply represents a starting point for a process that does not require a
prior condition in order for it to start. For example: processes (1) and (2) may start at any time
under the volition of the Supplier or the Customer.
An end state circle represents a condition of a function that does not cause any further
events in the system and is the logical conclusion of a process. For example: process (18)
ends at the Settlement function when the receipted payments from customers are handed to
the supplier and there are hence no further actions to be taken from that point.
Between the business functions and the support functions there is a common system state
(horizontal bar) that joins all the functions (1 to 17), and which serves to signify that the
support functions have a relationship with each of the business functions by means of the
support processes. However, each of the support functions in turn also has a relationship with
the other support functions by means of the support processes. For example: the Time
function serves the Accounting function with time information for controlling its time-based
tariff schedules and also serves the Recording function with date and time information for
tagging the data records where applicable.
6.1.2 Composition of the reference model
The multitude of functions in a payment metering system can be grouped and then abstracted
into generic functions as depicted in Figure 3. This abstract function model is thus a generic
representation of the functions in a payment metering system, from which all instances of
specific systems are derived. Each generic function is allocated a class number (1 to 17),
according to which all sub-functions are further classified, each sub-function thus inheriting its
class from its generic parent function. Functions of class 1 to 11 are the business functions,
while class 12 to 17 are support functions. A business function is one that implements
application-specific business-related logic, while a support function is one that enhances the
functionality of the business functions and also that of other support functions. It can thus be
seen that one business function has a very specific interactive relationship with another
business function, while a support function has a more general relationship with other
functions and may interact with any other business function or with any other support function.
6.2 Business functions
The business functions are those that participate directly in the business rules of the
application and enable the system to do what it is designed for. Thus they facilitate the
delivery of goods and services in terms of the conditions of the supply and purchase
agreement between the Supplier and the Customer.
With reference to Figure 3, the generic payment metering system application process employs
the following generic business functions.
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