APPLYING BLOCK ACTIVITY PATTERNS IN

WORKFLOW MODELING

Lucinéia Heloisa Thom, Cirano Iochpe

Institute of Informatics, Federal University of Rio Grande do Sul, Av. Bento Gonçalves 9500, Porto Alegre, Brazil

Keywords: Business process types, block activity, workflow patterns, business/workflow process modeling.

Abstract: This paper discusses a set of business (sub-)process types represented as “workflow block activity patterns”.

We describe all patterns in a common language (UML 2.0) and through some study cases we tried to find

out whether they are frequently reused during business/workflow process modeling. The results showed that

the patterns are frequently identified in both workflow elements and workflow applications. We believe they

can be reused to improve the quality as well as the performance of the design phase in a workflow project.

1 INTRODUCTION

In the last years, research on workflow patterns has

increased mainly because of the reuse advantages

that patterns can establish (Thom, 2005), (Hohpe,

2004). The most expressive approaches are in the

field of control/data flow patterns (Aalst, 2003),

(Russell, 2004) as well as resource and application –

oriented patterns (Russell, 2004b). However, a lot

less research can be found relating workflow design

to a set of recurrent business process “pieces” that

must be atomically executed by the workflow

process. Although one can precisely characterize the

semantics of such business process “pieces”

(Medina, 1992), (Malone, 2004), (Muehlen, 2002)

and they have to be recurrently re-designed in

practically every workflow modeling process, there

is no known research relating these business process

structures to workflow patterns.

1.1 Approach

An activity set is a self-contained set of activities

and transitions (WfMC, 2005). Transitions in the set

should refer only to activities in the same set and

there should be no transitions into or out of the set.

Activity sets can be modeled as block activities. The

block execution starts at the first activity in the set

and executes next activities by following the partial

order established upon them by the transitions until

it reaches an exit activity. Workflow execution then

returns to the next activity following the block.

The approach we undertake in this paper applies

the block activity concept in order to represent a set

of business process types found in the literature

which we call then “workflow block activity

patterns”. According to (Gamma, 1995) a pattern is

the abstraction from a concrete form which keeps

recurring in specific non-arbitrary contexts.

The block activity concept is suitable for

representing the selected business process “pieces”

because it can encapsulate their well-defined

semantics as well as represents their atomic

characteristic. It means that all activities defined

inside the block activity pattern must execute before

workflow continues execution.

Since our patterns representations may require

input/output parameters and the block activity

concept does not support parameters, we apply the

transaction perspective of the serializability theory

to overcome this limitation (Bernstein, 1987). An

input parameter is represented as a database read

operation of a “one-time-only” readable information.

Similarly, an output parameter is represented in the

block as a database write operation of a “one-time-

only” writeable information.

As part of our investigation, after integrating

different pattern classifications found in the

literature, the so-called workflow block activity

patterns were described in a common language. The

UML 2.0 (OMG, 2005) was chosen for this purpose.

In order to verify whether these workflow patterns

are modeled as often as their counterparts in

business processes, we conducted some case studies

by analyzing both a set of workflow definition

457

Heloisa Thom L. and Iochpe C. (2006).

APPLYING BLOCK ACTIVITY PATTERNS IN WORKFLOW MODELING.

In Proceedings of the Eighth International Conference on Enterprise Information Systems - ISAS, pages 457-460

DOI: 10.5220/0002448004570460

 SciTePress

languages and a set of workflow processes.

1.2 Related Work

Wil van der Aalst proposed 21 workflow patterns for

the description of business process behavior (Aalst,

2003). More recently, Aalst proposed a set of

workflow data patterns (Russell, 2004) and a set of

resource workflow patterns (Russell, 2004b). Our

approach differs from Aalst’ approach because each

of our pattern have content and context based on

specific business functionality (e.g., task execution

request and informative communication)

SAP created a cross-application tool called SAP

Business Workflow. The tool makes feasible the

integration of business tasks between applications

including a workflow wizard with workflow

templates (Andrews, 2003).

The Massachusetts Institute of Technology (MIT)

started in 1991 the Process Handbook development,

an online knowledge base including entries for over

5000 business activities (Malone, 2004). We

consider our patterns more application independent

then SAP and MIT patterns.

The remainder of the paper is structured as

follows. Section 2 brings an overview about

different business process types. Section 3 describes

some of these process types through UML 2.0.

Aiming to investigate whether they are implemented

in workflow components of different workflow tools

as well as different applications a matching exercise

was performed. The results of it are summarized in

Section 5. Finally, Section 6 concludes the paper and

brings future directions.

2 BUSINESS (SUB-)PROCESS

TYPES

The participants of a process communicate by

exchanging messages. According to (Hope, 2004) a

message exchange includes two roles: a sender or

producer (sends a message) and a receiver or

consumer (receives a message). Furthermore, a

message comprises two parts, a header and a body.

The header contains meta-information about the

message (e.g., who send it and where it is going).

The body is formed by: (a) a data; (b) an activity

execution/information request or; (c) a notification.

In (Muehlen, 2002) messages are classified in

unidirectional and bi-directional. Unidirectional

messages are used either by a sender to request the

execution of an activity from a receiver, or by a

receiver to notify a sender. Bi-directional messages

either form a request/respond pair, where a sender

asks a receiver to perform an activity and the

receiver answers the sender, or they form a

solicit/respond pair, where a receiver asks the sender

for information which is supplied subsequently.

Communication processes are characterized by

the exchange of messages between at least two

participants of the process. In the literature we found

four mainly different kinds of communication

processes (performative unidirectional/bi-

directional, informative and notification) (Geurts,

2004).

A performative communication process refers to

an activity execution request being either

unidirectional or bi-directional. By the other hand,

an informative communication process comprises an

information (e.g., data) required by some process

participant, i.e., aims at the sharing of existing

knowledge (Muehlen, 2002), (Medina, 1992). A

notification process, in our approach differs from an

informative communication process because it

comprises only process execution status.

When a process includes physical tasks it is

called material process (Medina, 1992). The

manufacturing, storage and transport of physical

objects are examples of material processes.

However, when the process is characterized by tasks

such as the buying and selling of goods it is called

logistic process (Muehlen, 2002). By the other hand,

when a monetary value is exchanged between two

parties it is called financial process (Muehlen,

2002). Finally, the process can includes a decision

making, i.e, a cognitive process of selecting a course

of activities from among multiple alternatives

(OMG, 2005).

(a)

(b)

(c)

(d)

(e)

(f)

(g)

Figure 1: From right to left (a) InitialNode; (b) Action –

refers to an atomic activity; (c) ForkNode or AND-Split;

(d) JoinNode; (e) ControlFlow (f) ActivityPartition or

Swimlane; (g) ActivityFinalNode.

3 BLOCK ACTIVITY PATTERNS

Within the context of a business as well as workflow

process there are a variety of different business

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458

process “parts” which can be understood as self-

contained activity blocks with a specific and well

defined semantic. It is worth observing that the same

“part” can be repeated within the same process. At

execution time different copies of a same “part” may

be receiving either the same or different parameter

values.

Due to space limitation, this section presents only

2 patterns in UML 2.0 notation. We rely on the

block activity concept of the WFMC to model

structures which should be executed atomically.

Figures 2 and 3 must be read according to the legend

presented in Figure 1. We used the Visual Paradigm

for UML Community Edition based on UML 2.0 as

an editor tool to design the patterns.

3.1 Unidirectional Performative

Communication Pattern

This pattern represents a unidirectional performative

communication process. As shows in Figure 2,

firstly there is an activity execution request. Based

on the activity description, a work item is assigned

to a receiver. After that, the process can continue

execution without waiting for response. The write as

well as read activities would be modeled as

parameters if allowed by a block activity.

Figure 2: Unidirectional performative communication

pattern.

3.2 Notification Pattern

The notification pattern (illustrated in Figure 3) is

based on the notification process type. It comprises a

notification activity that can either inform the end of

an activity execution or post news inherent to the

workflow application. In the last case, the sender

usually sends a notification. In our approach we are

treating the notification activity as a self-contained

activity because we consider that a notification

activity status can, eventually, be sent after

previously being requested to do so.

Figure 3: Notification pattern.

4 CASE STUDY

Aiming at identifying the patterns introduced in

Section 3 in real processes we performed a

“matching exercise”. Firstly we searched for

individual as well as combinations of patterns in the

workflow modeling language supported by the

Oracle Workflow Cartridge (Oracle Guide, 2001).

After that, we tried to find the same patterns within a

set of real workflow processes that were modeled as

well as implemented with that tool. In a third step

we analyzed the set of JBoss (Jboss, 2005) modeling

elements. Due to the lack of space, in the following

we present only an example concerning the process

for the evaluation of new products that are supposed

to be in the market. The process (see Figure 4) starts

with a notification to a process participant who is

responsible for the launching evaluation. After that

the system notifies the Financial department whether

the product was accepted or not.

Figure 4: Launching of new products.

In this process we identified the notification

patter (represented as a square) and the bidirectional

performative communication.

5 CONCLUSIONS

This paper presented an overview of the main

business process types found in the literature

represented as “workflow block activity patterns”.

Through some study cases they were identified both

in workflow components from different tools and in

workflow applications. The main results of the

“matching exercise” were: (a) the patterns could be

APPLYING BLOCK ACTIVITY PATTERNS IN WORKFLOW MODELING

459

identified in most of the analyzed workflow

elements. Accordingly, we perceived that they are

probably present in workflow applications

developed with bases on such workflow elements;

(b) the patterns were also identified in specific

“pieces” of a workflow application which makes

feasible their reuse in similar new applications.

By applying the WfMC “activity block” concept

in the patterns definition we provide the atomicity

property, meaning that whole activities inherent to a

specific patter are completely executed from

beginning to end before the flow (outside the

activity block) can continue. Additionally, the

serializability theory was also suitable to cover the

parameter expression limitation of the block activity.

Each of our patterns present a well-defined and

usefulness semantic referring to some specific “part”

of the business (sub-)process. We also highlight that

our patterns are conceptual level -oriented patterns,

thus they are suitable to be used during the workflow

design phase. With the patterns being proposed we

aim to improve both the quality and the performance

of the modelling phase in a workflow project mainly

because of the reuse advantages of pattern

approaches.

As future work we intend to continue

investigating both workflow elements of different

tools and workflow applications of different

domains. The advantage of that approach is twofold:

firstly it showed to be an interesting way to evaluate

the workflow tools; secondly, it can leads to the

discovering of new patterns.

ACKNOWLEDGEMENTS

The authors acknowledge the German Academic

Exchange Service – DAAD, the Coordination for the

Improvement of Graduated Students – CAPES

(Brazil), the Institute for Parallel and Distributed

Systems – IPVS of University of Stuttgart (Stuttgart,

Germany) and the Informatics Institute of Federal

University of Rio Grande do Sul – UFRGS (Porto

Alegre, Brazil).

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