What is the relationship between ALE and middleware in SAP?

For distributed business processes many different services are required. Most of these services are offered by SAP. For some of these services you can also use products that are provided by SAP's complementary software partners or by other companies:

The communication service for doing the pure communication is usually done via Remote Function Call (RFC).

RFC is provided by SAP for most platforms both for synchronous and asynchronous communication. There are other messaging systems for the communication service available as well, like IBM's MQSeries.

However, the communication between SAP and the messaging system is still done via RFC.

For the serialization of asynchronous communication the RFC provides little functionality at the moment.

The serialization has to be checked by the application. ALE offers some support to do these checks.

The serialization of the RFC communication will be improved in the future. Serialization services are provided by some of the existing messaging systems, but even they can not guaranty a 100% serialization of the communication, since they use RFC for the connection to SAP.

The monitoring and error handling of the communication is done via services provided by the RFC and ALE. If messaging systems are used for the communication they also offer some monitoring and error handling functionality.

If a non-SAP system is involved in the ALE business scenario and this system does not understand SAP's BAPI or IDoc interfaces, the data has to be mapped to any interface structure that this system offers.

For this mapping SAP does not provide a service but it certifies mapping tools from software partners. These tools are called ALE translator. The most known product in this area is probably Mercator from TSI International Software. The same kind of mapping can also be done by 'EDI converters'.

Another type of middleware products offer process ware. This is mainly a combination of the communication service, the mapping service and a set of rules for the mapping. Some ALE translator can be used for this as well.

Receiver determination is one of the ALE services (see above). Parts of this service can also be provided by some of the messaging systems, but you cannot use these systems without using ALE receiver determination.

For the other ALE services like application monitoring, application error handling, semantic synchronization and business process harmonization, there are no middleware products available as a replacement of ALE.

ALE is open for the use of middleware products for the distribution, but in most cases the additional middleware is not necessary.

In a communication between different SAP systems usually the use of additional middleware makes no sense at all.

For the communication between SAP and non-SAP systems there might be some benefits, especially if the middleware is used at the company already. The only middleware tool that is really required if the non-SAP system does not understand BAPIs or IDocs is an ALE translator.