Database Reference
In-Depth Information
ESA applications are designed with shared application systems (or components) that are com-
bined together to form composite applications. The components expose a standard set of services
that are usable by various enterprise business processes. These standard services such as
create
Purchase Requisition
or
Issue goods from Inventory
are called enterprise services.
10.3.3 Enterprise Services Architecture (ESA)
In 2003, SAP introduced a revolutionary vision for the future of business applications called
Enterprise Services Architecture (ESA). ESA is a radical departure in technology architecture. The
ESA platform offers Web Services as a way to make IT environments more flexible with interoper-
ability and deployment of cross system functions. Simultaneously, it builds on existing solutions
to protect legacy investment while still providing innovative solutions. ESA is based on a service-
oriented approach to applications; ESA-based applications are designed with shared application
systems (or components) that are combined together to form composite applications. By eliminat-
ing much of the
impedance mismatch
between systems and business processes, ESA can yield much
greater agility while simultaneously achieving substantial reduction in TCO.
As discussed in Chapter 4, Section 4.5.1.2 “Integrated Best-in-Class Applications,” enterprises
are driven to select a composite of applications that best meet the specific needs of the enterprise in
different areas. The downside of this approach is the higher efforts and costs of integration. Also,
enterprises face increasing and ever-changing competition. To survive long term in the market,
they have to adopt themselves flexibly and quickly to the market conditions and to continually
develop innovative business solutions. Enterprises are also under tremendous pressure to reduce
costs; hence, replacing functioning systems with totally new solutions is not cost efficient (if not
impossible). The existing systems and infrastructures are incapable of supporting fast, flexible, and
cost-effective adoption to the changed or novel business processes or operational strategies. The
key to continuing success in such an environment is the capability with flexibility to use existing
infrastructures, capabilities, and processes within the context of new applications, that is, compos-
ite applications in the context of ESA.
An ESA platform provides flexible and unified access to the integrated functionality of het-
erogeneous system landscapes within enterprises and can be realized by using SAP NetWeaver.
The ESA application stack consists of the following layers:
◾
User interface layer
: This layer provides and manages the interaction with the user.
◾
Process layer
: This layer manages the sequence of steps carried out during runtime of the
application.
◾
Service layer
: This layer consists of all services that provide analysis and processing to busi-
ness objects.
◾
Object layer
: This layer combines data from different sources and basic access methods and
maps them to target business objects.
◾
Persistence layer
: This layer is responsible for the physical storage of data.
ESA platform is constituted of the data, the relevant services to work with these data, and processes
that span the sequence of access and processing of these data. The ESA model does not maintain its
own copies of business objects. Identified objects are mapped to their original sources in order to ensure
the currency and consistency of data as also to avoid redundant data. In case of the business processes,
ESA affects a clear separation between the process and the application logic, which enables mapping
of the complete processes. Extracting the application logic of the underlying systems and providing it
