Combining Rules and Activities for
Modeling Service-Based Business Processes


Milan Milanović1, Dragan Gašević2, Gerd Wagner3
1FON-School of Business Administration, University of Belgrade, Serbia
2Athabasca University, Canada
3Brandenburg University of Technology at Cottbus, Germany
milan@milanovic.org, dgasevic@acm.org, wagnerg@tu-cottbus.de


Abstract

It is widely acknowledged that business process
management would greatly benefit from integration
with business rule management. But there is still no
established solution to this integration problem, and
the leading business process modeling language,
BPMN, does not provide any explicit support for rules.
In this paper, we are going to investigate the extension
of BPMN by adding rules as a modeling concept in the
form of a new gateway type, using the principles of
Model-Driven Engineering. The integration will be
done on the level of the metamodels of the involved
languages, resulting in a new rule-based process mod-
eling language called rBPMN (Rule-based BPMN).


1. Introduction

Recent research [26] has identified a lack of explicit
formalism in the process modeling languages for cap-
turing business rules. In this paper, we follow the busi-
ness rules approach [5] by combining business process
models and business rules in a way that makes rules
first-class citizens in business process modeling. The
key idea is to extract some parts of a business logic
contained implicitly in business process models into
explicit definitions of business rules. To achieve this,
we propose adding a new gateway type, called rule
gateway, to the business process modeling language
BPMN. We also discuss how Web service composi-
tions can be extracted from such rule-based process
models and discuss a set of business process modeling
(workflow) patterns for modeling SOAs. By adding
rules to the BPMN we enable run-time updates of a
business logic, which with regular BPMN cannot be
done.
Our high-level modeling approach allows develop-
ers to focus on a problem domain rather than on an
implementation technology. Following the principles
of Model Driven Engineering (MDE), we integrate a
new rule gateway type into BPMN business process
models on the metamodel level, resulting in a language
called rBPMN (Rule-based BPMN), which facilitates
business process modeling by domain experts and al-
lows to transform such process models into different
SOA implementation platforms [7].
In order to make such abstract business process de-
finitions modeled by business expert’s executable, the
ability to integrate heterogeneous enterprise systems is
needed. Web Services (WS) technology provides this
ability by encapsulating enterprise systems functionali-
ty into services. Service composition languages, such
as the Business Process Execution Language (WS-
BPEL [11]) and service interaction protocol languages
such as the Web Services Choreography Description
Language (WS-CDL [12]), make it possible to com-
bine different services and to automate and standardize
the execution of cross-organizational business process
models [10]. Web services, service composition lan-
guages and service interaction protocol languages are
key technologies for enabling SOA. In our approach,
we propose obtaining service compositions from rule-
based business process models to make those process
models executable.
The rest of the paper is structured as follows. In the
next section, a motivating example is presented which
is used to explain different concepts used throughout
the paper. In Section 3, requirements for modeling
rule-enabled SOAs are given, together with proposed
methodology for developing rule enabled SOAs. Sec-
tion 4 introduces MDE, business rules and business
process languages. In Section 5, we present different
business process modeling patterns that our solution
needs to support and rBPMN language. Before con-
cluding the paper in Section 7, in Section 6, we sum-
marize the related work.