There are two distinctions that are applied to knowledge—implicit and explicit (knowledge representation domain).
It is believed that understanding of any domain is achieved through an explicitation process wherein an implicit body of knowledge is transformed into an explicit body of knowledge.
What do we mean by explicit knowledge. Encoding is one form in which knowledge is explicitly represented. But then why does the act of doing or performing is not considered as an explicit form of knowledge. In early period, in ancient India knowledge was transferred by chanting (for lessons on vedas) by doing (skills of pottery, etc.) Both these forms were confined within their own families/groups. This knowledge never travelled out of their confined circles, and it also had a limited life. In this way the knowledge which was implicitly known was used for various purposes. But inorder that the knowledge is transferred it is very important that it becomes explicit by encoding. In this way the explicit knowledge which is encoded in a writing form provides access to this piece of knowledge in all parts of the world (and is not merely confined). Once we have the access, it is also possible to reproduce and verify the knowledge.
Therefore, when a knowledge has to be explicit then it needs to follow the criteria of encoding, accessibility, reproducibility, verifiability.
humans are mortal, but code (knowledge) is immortal.
the above points are based on a discussion over breakfast table (Nagarjuna, Ritesh, myself).