The ordering process shown can be used as a blueprint that allows the
reseller company to organize its work. The company will receive many orders,
each of which can be processed as described in the blueprint. This observation
gives rise to important concepts in business process management: business
process models and business process instances.
The blueprint shown in Figure 1.1 is the business process model. Each
order that is processed according to this model is a business process instance.
Therefore, there is a one-to-many relationship between business process models
and business process instances. Conceptual models of business process
models and instances will be the subject of Chapter 3.
Definition 1.4 A business process model consists of a set of activity models
and execution constraints between them. A business process instance represents
a concrete case in the operational business of a company, consisting of
activity instances. Each business process model acts as a blueprint for a set
of business process instances, and each activity model acts as a blueprint for
a set of activity instances.
If no confusion is possible, the term business process is used to refer to
either business process models or business process instances. Analogously,
activity is used to refer to either activity models or activity instances.
Business process models are the main artefacts for implementing business
processes. This implementation can be done by organizational rules and policies,
but it can also be done by a software system, using a business process
management system. In this case, according to Definition 1.3, the software
system is driven by explicit process representations.
The business process model shown in Figure 1.1 can be used to configure
the business process management system accordingly. The resulting system
makes sure that all business process instances are executed as specified in the
business process model and that, for instance, after receiving an order, the
Send Invoice and the Ship Product activities are executed concurrently.
Since business processes are performed in a single organization by definition,
the ordering of activities can be controlled by a business process
management system as a centralized software component run by the reseller
company. This centralized control is very similar to a conductor who centrally
controls the musicians in an orchestra; therefore, business processes are also called process orchestrations. Chapter 4 will investigate languages to express
process orchestration.
The business process model shown in Figure 1.1 represents activities that a
reseller performs to process an incoming order. This business process interacts
with the business process of a corresponding buyer. The buyer sends an order,
receives payment information, settles the invoice, and receives the ordered products.
The business process of the buyer is shown in Figure 1.2. It starts with its
placing an order, before two concurrent branches are opened. In one branch,
the invoice is received and the invoice is settled. In the other branch, the
product is received. When both branches complete, the business process of
the buyer completes.
Definition 1.1 indicates that each business process is enacted by one organization,
and that business processes can interact with each other. The business
processes of the reseller and the buyer can, for instance, interact with each
other in the following way.
1. The buyer sends an order message to the reseller (Place Order activity).
2. The reseller accepts the order message in the Receive Order activity. The
order information is then extracted from the message, and order processing
continues.
3. The reseller sends an invoice (Send Invoice) and ships the ordered products
(Ship Products).
4. The buyer receives the invoice in the Receive Invoice activity.
5. The buyer sends the payment in the Settle Invoice activity.
6. Finally, the buyer receives the ordered products in the Receive Products
activity.
The interacting business processes are shown in Figure 1.3. Interacting activities
of the reseller business process and the buyer business process are related
to each other by dotted arcs, representing the flow of messages. Message flow
can represent electronic messages sent, but also the transport of physical objects,
such as ordered products.
The interactions of a set of business processes are specified in a process
choreography. The term choreography indicates the absence of a central agent that controls the activities in the business processes involved. The interaction
is only achieved by sending and receiving messages. In order to realize correct
interactions, the interacting business processes need to agree on a common
choreography before they start interacting.
This situation is similar to dancers who need to agree on a common choreography
before the show starts. During the performance, however, each dancer
behaves autonomously but in line with his or her part in the choreography.
Process choreographies will be discussed in detail in Chapter 5.
The representation of the business process choreography is shown in Figure
1.3; it also represents start events and end events of the interacting business
processes, marked by circles.
This process choreography allows for multiple concrete implementations,
in which the degree of software support can differ. Traditional ways of ordering
goods that are not supported by information systems are well captured by this
business process interaction. A buyer browses a paper catalogue of a reseller,
selects a set of products, fills a postcard with ordering information, and sends
the postcard to the reseller.
This postcard effectively implements the message flow from the buyer to
the reseller. On receiving the postcard, the reseller sends the products and
the invoice. The buyer receives the products and, assuming everything is fine,
settles the received invoice, for instance, by money transfer. Once the money
arrives at the reseller, the interacting business processes complete.
Pressing the submit button submits the order, i.e., it realizes the message
flow from the buyer to the reseller. The message flow from buyer to reseller
is no longer implemented by surface mail, but by Internet protocols. The
buyer’s Web browser sends a message to the reseller’s Web server, which calls
a software module that places the order in the reseller’s ordering system.
In case intangible goods have been ordered, such as music or software,
sending the products can also be realized by software systems. The same
applies for invoicing and billing, where online billing services can be integrated into the business process.
Graphical representations of business processes, as shown in the examples, focus on the process structure and the interactions of the participating parties rather than on technical aspects of their realization. This is an important aspect in business process modelling, since the definition of business processes and their interaction behaviour does not prescribe certain implementation
strategies or platforms.
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