2.2 Enterprise Applications and their Integration
2.2.1 Enterprise Resource Planning Systems
In this setting, Enterprise Resource Planning systems (ERP systems) were developed. The great achievement of enterprise resource planning systems is that they provide an integrated database that spans large parts of an orga- nization. Enterprise resource planning systems basically reimplemented these
Fig. 2.2.Enterprise applications with redundant data and data dependencies
disparate enterprise application systems on the basis of an integrated and consistent database.
An enterprise resource planning system stores its data in one centralized database, and a set of application modules provides the desired functionality, including human resources, financials, and manufacturing. Enterprise resource planning systems have effectively replaced numerous heterogeneous enterprise applications, thereby solving the problem of integrating them.
Fig. 2.3.Two-tier client-server architecture
Enterprise resource planning systems are accessed by client applications, as shown in Figure2.3. These client applications access an application server
that issues requests to a database server. We do not address the architectures of enterprise systems in detail but stress the integrated data storage and the remote access through client software.
With the growth of enterprises and new market requirements, driven by new customer needs around the year 2000, the demand for additional function- ality arose, and new types of software systems entered the market. The most prominent types of software systems are supply chain management systems, or SCM systems, and customer relationship management systems, or CRM systems. While basic functionality regarding supply chain management has already been realized in enterprise resource planning systems, new challenges due to increased market dynamics have led to dedicated supply chain man- agement systems. The main goal of these systems is to support the planning, operation, and control of supply chains, including inventory management, warehouse management, management of suppliers and distributors, and de- mand planning.
Regarding the evolution of enterprise systems architectures, the main point is that new types of information systems have entered the market, often de- veloped by different vendors than that of the enterprise resource planning system many companies run. At the technical level, the supply chain manage- ment system hosts its own database, with data related to supply chains. Since large amounts of data are relevant for both enterprise resource planning and supply chain management, data is stored redundantly. As a result, system ar- chitects face the same problems as they did years ago with the heterogeneous enterprise applications.
As with the settings mentioned, in order to avoid data inconsistencies and, at the end of the day, dissatisfied customers, any modification of data needs to be transmitted to all systems that host redundant copies of the data. If, for example, information on a logistics partner changes that is relevant for both the enterprise resource planning system and the supply chain management system, then this change needs to be reflected in both systems. From a data integrity point of view, this change even needs to take place within a single distributed transaction, so that multiple concurrent changes do not interfere with each other.
The source of the problem is, again, redundant information spread across multiple application systems. Since this information is not integrated, the user of an enterprise resource planning system can access only the information stored in this system. However, the customer relationship management system also holds valuable data of this customer.
When the customer calls and the call centre personnel can only access the information stored in one system, and is therefore not aware of the complete status of the customer, the customer is likely to become upset; at least, he does not feel well served. The customer expects better service, where the personnel is aware of complete status and not just of partial status that happens to be stored in the software system that the call centre agent can access. In the scenario discussed, the call centre agent needs to know the complete status of
the customer, no matter in which software system the information might be buried.
To characterize this unsatisfactory situation, the termsiloed applications has been coined, meaning that data is stored redundantly in different systems, and these systems are not related at all. Figure 2.4 shows siloed enterprise applications customer relationship management, supply chain management, and enterprise resource planning systems. While these application systems can be physically connected by, for instance, a local network, they are not logically integrated.
As a result, the only way to integrate the information stored in these sys- tems is through the user, who accesses the information in the various systems and does the integration manually. Obviously, this manual integration con- sumes considerable resources and is error-prone, so that other solutions are sought.
Fig. 2.4.Siloed enterprise applications
With enterprise resource planning systems, this problem had already been solved by redeveloping an integrated solution. Unfortunately, due to the large complexity of the systems at hand, the same approach to reimplementing systems functionality in an integrated way is not feasible in the new context.
The only option is to integrate these systems, which leads to a new breed of middleware system, the enterprise application integration system.