Software maintenance presents nowadays one of the most critical phases of software system life cycle. Constant changes of system's requirements or changes related to occurrences of system defects caused that thorough system understanding in order of efficient realization of system's modifications becomes now an inevitable part of maintenance process.In this paper, we emphasize the importance of system's comprehension in the context of an early detection of system's defects by offering the description of its life cycle and classification, but mainly by introducing the principles of architectural knowledge concept. We also propose a new approach of dealing with one of the currently most serious obstacles inhibiting this concept from its further use -the problem of architectural knowledge automatic acquisition.Index Terms-Knowledge, software defect life cycle, software maintenance, architectural knowledge, architectural knowledge acquisition process.