1 An Enterprise Layer based Approach To Application Service Integration Wilfried Lemahieu, Monique Snoeck, Cindy Michiels Department of Applied Economic Sciences Naamsestraat 69, 3000 Leuven, Belgium email: {wilfied.lemahieu, monique.snoeck, cindy.michiels}@econ.kuleuven.ac.be This paper is forthcoming in Business Process Management Journal, Special issue on ASP Abstract. Today many companies rely on third party applications and application services for (part of) their information systems. When applications from different parties are used together, an integration problem raises. In this paper we describe an integration approach based on the construction of an enterprise layer. This approach is deliberately kept away from a document based, flow-oriented approach were business processes are hard coded into the application architecture. Interaction is based on the concurrent update of a shared underlying enterprise layer. At the same time, the application architecture becomes easily adaptable to re-engineered business processes. Keywords: Business Process Modelling, Domain Modelling, Application Integration, Object Oriented Analysis 1. Introduction The dramatic advance in Information and Communication Technology over the past decade allows for innovative organisational forms that were unthinkable before. Whereas most companies used to develop all the required business information systems support in-house, the need for shorter software life-cycles, the shortage of IT skills and the increased affordability and ability to amortise the cost of business solutions drives more and more companies to buy or rent the required software as applications or application services from Application Providers. In the best case, a single software product line is available for the entire company. In many cases however, the company will have to rely on the services of different providers for one or more functional domains. When a company obtains its software from different providers a number of problems must be solved: - Software has a significant impact on the ways of working of an enterprise and shapes the possible business processes of the organisation. An approach of one software package per functional unit suits the more functionally oriented organisational forms. A more process-oriented organisational form with enterprise-wide integrated processes is much less well supported. If a process-based organisation wants to successfully integrate applications from different providers, it first must integrated the business processes from the different applications. - Besides integrating applications from an organisational point of view, the information management aspects must also be integrated. Each application maintains it owns data, but often data will be replicated across different functional domains. For example, data about "products" and "customers" will appear in the Sales & Marketing, Service Provisioning, Customer Services and Financial domains. An integrated process-based approach requires an integrated information management support (Seltsikas, 1999). Replication of data must be carefully managed and avoided whenever possible as it is likely to cause errors in the processes and complicates successful automation of business processes. - Third-party applications that support (part of) the core business processes of a company also maintain valuable core information. If after some time the company wishes to switch to another application service provider, the question raises how to recover this core information and how to merge it into the new application.