One of the challenges in
designing distributed applications is the data distribution model, which
consists of all participating systems and the messages to be exchanged by
the system. Data distribution in R/3 to R/3 environment is easily achieved
but there are several bottlenecks in R/3 to non-R/3 scenarios – for example
data mapping - as non-R/3 systems seldom have as rich an organizational
representation as R/3 has. The following figure illustrates the concept of
data distribution using ALE.
Figure 1: ALE FRAMEWORK
Enterprise business objects
of a SAP system are distributed with the help of BAPIs (Business Application
Programming Interfaces). ALE acts as a layer that incorporates the
inter-linking of business objects at the application level. The ALE layer
provides the following services:
Applications services: this layer provides ALE with
an interface (for instance: BAPI) to R/3 to facilitate data exchange to
or from external R/3 systems.
Distribution services: the onus of filtering and
converting messages exchanged between SAP and non-SAP systems is on the
distribution layer of ALE. This service is the core service and acts as
a sandwich layer between application and communication layers.
Communications services: ALE supports synchronous as
well asynchronous communication. Synchronous messaging is used for the
direct reading of control data, while asynchronous messaging is used for
transmitting or receiving application data.
The implementation of ALE is achieved with
the help of external converters (ALE converters), which connect SAP
applications to non-SAP applications. In simple words, external converters
are generic-format conversion programs, which contain specific converter
functions. The capabilities of the external converter will be discussed
later in this article.