Today's enterprise application landscapes are characterized by a variety of different technologies and concepts for distribution. On one hand, this variety arises within the enterprise organization itself for historical reasons, personal preferences of different people, and the dynamics of acquisitions and mergers. As a matter of fact, many redundant concepts exist within the same organizational unit. On the other hand, complementary concepts and technologies also exist. Due to the requirements of different types of distribution problems that coexist in one corporation, different solutions arise as well.
A modern architecture must be able to embrace all these technologies and concepts. Heterogeneityincluding heterogeneity of middlewaremust be understood as a fundamental fact that cannot be fought but instead must be managed. Furthermore, an architecture must accommodate frequent changes of the underlying distribution infrastructure. As a matter of fact, the lifecycles of today's infrastructure products are largely incompatible with the lifecycles of enterprise applications. Thus, you must protect the assets of an existing application landscape and simultaneously take advantage of the latest infrastructure products.
In this chapter, we have discussed the necessity of carefully choosing the right approach to integrating two distributed software components. Among other issues, you must decide on the appropriate communication infrastructure, synchrony, call semantics, usage of an intermediary, and object-oriented versus data-centric interfaces. All these decisions impact the coupling of the two systems.
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 Often referred to as TP monitors, TPMs, or TX monitors.