explanations. First of all it depends how the knowledge in an organization is organized. Hansen et al. (1999) made a distinction between a codification and personalization strategy. A codification strategy focuses as the word already implicates, to codify knowledge in a company, where a personalization strategy implies personal interaction as the main factor for exchanging knowledge. Both strategies have their problems. First of all it is in many cases not possible to codify knowledge because of e.g. codifiability and complexity (see Kogut and Zander, 1992 for a very clear and elaborated study on this subject). This is called cognitive limitations (Hinds & Pfeffer, 2001). Hinds & Pfeffer (2001, pp4) argue that : "As expertise increases, mental representations become more abstract and simplified" And even if people can share knowledge, sometimes they do not want to. Hinds & Pfeffer (2001) call this motivational limitations. Hall et al. (2001) see rewards and informal activities with colleagues as the solution for the so-called motivational limitations. They divided the rewards in two groups, the explicit and the soft rewards. Explicit rewards are e.g. economic incentives and career advancement. Soft rewards are non-economic rewards such as reputation and satisfaction. Formal and informal knowledge sharing All this theory is based on formal structures in an organization. Organizations all also exist out informal ties and networks. This complicates organizational goals of formal knowledge sharing. A company will lose track of who has what knowledge because of the informal networks. This does not mean that informal networks are negative, just on the contrary, informal networks can create ties and surroundings which are necessary for knowledge sharing (see Brown & Deguid, 2001). Informal networks have received different names in the literature such as sensemaking (Weick, 1979), communities of practice (Brown & Deguid 1998) and communities of knowing (Boland &Tenkasi, 1995), Nikolai Groups (Nikolaivitch 1956). As Pan & Leidner (2003) argue in their paper, communities of practice exist because functional boundaries do not fit the community boundaries. They state (pp 73): “facilitate an environment of 'structured informality' supported by knowledge, people, organizational processes and infrastructure.” The implication and unfortunately also the complication of informal networks is that an organization loose the general view of the knowledge in the organization. As showed by Cross et al. (2001) an informal structure significantly differs of the formal one. To effectively maximize the potential the authors argue that it is necessary to analyze both