A model of knowledge conversion
The SECI model  is a part of Nonaka's model of knowledge creation in organisations. According to this model organisations create knowledge through interaction between explicit and implicit knowledge which is called conversion. SECI model describes how knowledge is created in this knowledge conversion process, see Fig 1. 
Modes of knowledge conversion
- Tacit to tacit (Socialization): Knowledge is acquired by social interaction and is available as implicit knowledge
- Tacit to Explicit (Externalization): Implicit knowledge is captured, codified and thus transferred to explicit knowledge
- Explicit to Explicit (Combination): The newly acquired codified knowledge is combined with already available explicit knowledge
- Explicit to Tacit (Internalization): New knowledge is learned (internalized) and available as tacit knowledge, and may be transferred by socialization
Explicit and tacit knowledge thereby interact with each other in a continuous process. Knowledge, which is held by individuals as tacit knowledge, is shared with other individuals, groups or organizations, and interconnects to generate new knowledge. This process may be viewed as a "spiral" or an "amount" of knowledge, which grows as the four stages are repeatedly run through.
Tacit to tacit: Socialization
Tacit knowledge is transferred by socialization processes such as interactions, observations, discussions, or working in same environment, either by face-to-face communication or by sharing common experiences. Tacit knowledge is often transferred in informal networks involving day-to-day interaction between people within work environments. Sources of new tacit knowledge outside an organizations may come from cooperation between organizations, conferences, workshops and other networking activities.
Foundation for socialization processes to work is an organizational knowledge sharing culture based which supports and promotes knowledge sharing. An organization may foster informal networks by providing spaces where people can engage in unstructured or unmonitored discussions, and by allowing a high degree of freedom in work practices to encourage creative problem solving.
In addition, more specific methods and communication have been developed which support tacit to tacit knowledge transfer:
Tacit to explicit: Externalization
Externalization denotes the process of capturing and documenting the captured knowledge in a form which allows transfer to the organization's knowledge base, in general a document or content management system.
Explicit to explicit: Combination
The basis for this mode of transfer are the search and retrieval features of the organization's knowledge base. Document or content management systems use advanced indexing, searching, and retrieval mechanisms to support the user. However, search and retrieval of the IT systems available today, which mostly relies on full-text indexing, still needs to be configured by administrators to yield satisfactory results to the user. Metadata describing the entities in the database remain predominantly manual operations, as well as assessing the relevance, validity and actuality of the entities. A classification which reflects the organization's main structure and its knowledge domains is often the key to high quality search, and requires taxonomies or ontologies which have to be maintained manually (some systems offer limited support for this task, but fully automatic classification systems are still a long way off). The quality of the search is usually considerable enhanced by instruments such as directories, knowledge maps, corporate yellow pages, which require manual care and maintenance. Thus, even if IT systems are indispensable, humans (experts, knowledge managers, content managers, administrators) play an important role in ensuring that the knowledge is relevant, up to date and correct.
Explicit to Tacit: Internalization
Internalization is learning by assimilating new explicit information. As this information is available to everybody having access rights to the organization's knowledge base, the transfer of explicit to tacit knowledge may have a large multiplication effect. This provides the foundation for a learning organization, a concept which is continuing to gain wide acceptance.
 NONAKA, I., TAKEUCHI, H. (1995) The knowledge-creating company. How Japanese companies create the dynamics of innovation, Oxford University Press, Oxford.
 NONAKA, I. (2009). "Tacit Knowledge and Knowledge Conversion: Controversy and Advancement in Organizational Knowledge Creation Theory". Organization Science 20 (3): 635–652.
 Ikujiro Nonaka, Ryoko Toyama and Noboru Konno, SECI, Ba and Leadership: a unified Model of Dynamic Knowledge Creation, Long Range Planning, 33, 2000.