Organizations generally make use of two kinds of knowledge: formal and informal. The two can be distinguished based on the extent of documentation. Formal knowledge is usually contained in books and manuals. On the other hand, informal knowledge could include assumptions, ideas, and viewpoints. From an organizational perspective, it also includes the culture, the shared beliefs, the core values, and very often past experiences or contexts in which decisions were made. Examples of informal knowledge can be seen in answering questions like: "Why did we do it that way?"; "What happened the last time we tried this approach?"; "Who would I go to solve this problem?"; "How are things done around here?"; and so on. Anand et al., (1998) refer to this as “soft knowledge” or knowledge that cannot be easily communicated. This includes tacit knowledge, belief structures, intuition, and judgmental abilities. The label of organizational memory collectively describes both formal and informal knowledge primitives. Stein and Zwass (1995) define organizational memory as "the means by which knowledge from the past is brought to bear on present activities, thus resulting in higher or lower levels of organizational effectiveness".
Schmitt, Lawrence; Krovi, Ravi; and Ryker, Randy, "Towards An Architecture for Acquiring, Representing, and Mining Informal Knowledge" (1999). AMCIS 1999 Proceedings. 27.