Vertical abstraction in business process modelling is depicted in Figure 3.3, where distinct modelling subdomains are identified. As depicted, process modelling is at the centre of the modelling effort, because it also integrates the modelling efforts that are conducted in the other subdomains.
Function modelling, data modelling, organization modelling, and modelling of the operational information technology landscape are required to provide a complete picture of a business process. While these subdomains are the most important ones, additional subdomains can be defined if they are relevant. The functional model investigates the units of work that are being enacted in the context of business processes. The specification of the work can be done at different aggregation levels, from coarse-grained business functions to finegranular functions at the operational level that are realized by knowledge workers and information systems.
The specification of these functions can be informal, using English text or formal, using syntactic or semantic specifications of functions. While informal descriptions are mostly done at the coarse business level, more precise speci- fications are required in the software layer when it comes to implementation of certain functions using information systems. The investigation and proper representation of data in business processes is important, because decisions made during a business process depend on particular data values. Also data dependencies between activities need to be taken into account in process design, to avoid situations in which a function requires certain data not available at that time. The proper representation of the organizational structure of a company is an important requirement. Activities in the business process can then be associated with particular roles or departments in the organization. Many activities in a business process are performed by or with the assistance of information systems. The operational information technology landscape, i.e., the information systems, their relationships, and their programming interfaces, needs to be represented to use the functionality provided by the information systems. Process modelling defines the glue between the subdomains. A process model relates functions of a business process with execution constraints, so that, for instance, the ordering and conditional execution of functions can be specified. Data aspects are covered because particular process instances may depend on the structure and value of data involved in a particular business process. For example, in a credit approval business process, the type of approval depends on the credit amount requested. In addition, data dependencies between activities need to be taken into account in process model design.
From Business Functions to Business Processes
Value chains provide a high-level organization of the functions that an enterprise performs. To provide a more detailed view, these top-level business functions are broken down to functions of smaller granularity and, ultimately, to activities of operational business processes. Functional decomposition is the technique of choice. A partial functional decomposition of a value chain is shown in Figure 3.4, where a value system represents the highest level of aggregation.
The ordering of the value chains in the value system is not represented in this structure diagram because it does not have any formal meaning. There are complex interactions between these companies, so that, obviously, not all activities in the supplier value chain occur before all activities conducted by enterprise E.
The functional decomposition of the value chain of enterprise E is exemplified for one particular path of functions in the marketing and sales top-level business function. Among many other functions, marketing and sales includes a business function, OrderManagement, that contains functions related to the management of incoming orders. Order management is decomposed further into business functions for getting and checking orders. To check orders, they need to be analyzed, and there are functions for simple and advanced checking of orders. There are different symbols for business functions and for functions of the finest granularity: business functions are represented by rectangles, while functions of the finest granularity are represented by rectangles with rounded corners. Functions at the leaf level of the functional decomposition are also called activities. Traditionally, functional decomposition was used to describe enterprises based on the functions they perform. As discussed in Chapter 1, concentrating on the functions an enterprise performs and neglecting their interplay falls short of properly representing how enterprises work. Therefore, functional decomposition is used as first step in the representation of enterprises based on business processes.
Operational business processes relate activities to each other by introducing execution constraints between them. In principle, relating functions to business processes can be applied for different granularities of business functions. In case high-level business functions are considered, a textual specification of the process is used, since concrete execution constraints between their constituents are not relevant in coarse-grained business functions. Consider, for instance, the business functions incoming logistics and operations. At this very coarse level of functionality, no ordering of these business functions is feasible: both business functions are performed concurrently, and only at a lower level of granularity does a concrete ordering make sense. For instance, when the operations business function orders additional material, then there are concrete activities that have a concrete ordering. Within operations, an internal order is created and sent to incoming logistics. On arrival of this order, raw material is provided to operations. In case no raw material is available at the manufacturing company, an external order is created and sent to a supplier of the raw material. Therefore, business processes relate fine-grained business functions, typically the leaves of the business function decomposition tree.
The sample business process starts with analyzing the order, and then conducting either a simple check or an advanced check depending on the decision made during process execution. This process has a dedicated start event and a dedicated end event. The business process is started once the start event occurs; when it completes, an end event occurs. Events play a crucial role when interrelationships between business processes are expressed. A particular business function of higher granularity (CheckOrder) consists of fine-grained activities, which are related by execution constraints. However, the check order business function (and the business process that realizes it) is related to other business functions and their respective business processes. An example showing this situation is displayed in Figure 3.6, where a part of the value chain is shown, in particular, the business functions Receive Request, Request Analysis, and Quota Management are shown. Since there is a strict ordering between these business functions, an execution ordering relation is represented.