Enterprise SOA

What motivated the creation of ESA?

SAP cofounder Hasso Plattner conceived ESA as a solution to the increasingly unwieldy number of enterprise applications appearing in corporate IT environments. As we discussed earlier in this chapter, all the functionality necessary for a given process could no longer be contained within a single application.

Plattner originally conceived of ESA to support cross-applications that could cross the boundaries of the enterprise applications beneath them and combine pieces of functionality into a new application running above them. These became SAP's family of packaged composite applications which were branded as "xApps". The creation of xApps overcame several of the implicit assumptions underlying enterprise applications and the previous architecture that no longer applied in the modern business world.

First and most important was the idea of the database as the single point of integration. This was the dominant model during the era of client-server approaches in the late '80s and early '90s. When entering a purchase order into ERP, for example, that order is added to a database that everyone in the system can access. Anyone wishing to revisit that order later can easily retrieve it from the database. But when an xApp begins crossing the boundaries between applications, borrowing data and functionality from each, the customer data may exist in different places—in CRM, SCM, and ERP—and it may not be synchronized across the three, leading to the potential ...