Transformation Layer

The transformation layer is the "Rosetta Stone" of the system. It understands the format of all information being transmitted among the applications and translates that information on the fly, restructuring data from one message so that it makes sense to the receiving application or applications. It provides a common dictionary that contains information on how each application communicates outside itself (application externalization), as well as which bits of information have meaning to which applications (see Figure 9.5).

Figure 9.5. The transformation layer.

Transformation layers generally contain parsing and pattern-matching methods that describe the structure of any message format. Message formats are then constructed from pieces that represent each field encapsulated within a message. Once the message has been broken down to its component parts, the fields may be recombined to create a new message.

Most integration servers can handle most types of information, including fixed, delimited, and variable. Information is reformatted using an interface the user integration server provides, which may be as primitive as an API or as easy to use as a GUI.

Message layers generally store application information in a repository (see the section "Repository Services" later in this chapter) that keeps track of the source system, the format of the message, the target system, and the desired format of the target system. Transformation layers are vital because different systems deal with information in such different ways. For example, a SAP system tracks customer information in a manner very different from a Baan system. In order to exchange customer information between the two systems, the information must be reformatted. This reformatting, or transformation, may include a schema conversion and a data conversion. Reformatting ensures consistent application semantics between all integrated source and target applications.