A satisfactory definition of communication should describe the phenomenon of interest. A better model will both describe existing events and predict the characteristics of future communications. The best definitions would help explain what is occurring, as well as allow us to describe and predict. The model of communication as complementary informative processes is based on a set of requirements for a definition of communication and a precise definition of information. The precision in this model of information, combined with the precision of the definition of communication, allows us to state explicitly what is and what isn't information and what is and what isn't communication. One may then define a communication as what is transmitted from the beginning of one process to the output of a process with the inverse functionality of the first process.
Most phenomena referred to in the form ``X to X communication," such as ``human to human communication" or ``machine to machine communication," are communication under our definition of communication. These expressions imply communication between the same levels of two different hierarchies, or, more formally, between a function f() and its inverse f-1().Defining communication as two complementary processes allows us to both predict what will happen in the presence of noise or the failure of functions to be exact inverses. One can also understand the human aspects of communication, as well as the low level biological and physical phenomena such as speech or hearing and the physical transmission of sound through the atmosphere or the transmission of words through the movement of written pages.
Our precise definition allows us to include phenomena as well as to exclude phenomena. A definition (such as ours) of a phenomenon central to a discipline such as communication may diminish or exclude some phenomena in two ways: by saying that something isn't the concept being defined, or that a characteristic isn't an intrinsic part of the phenomena being defined, decreasing its importance to the definition and to the field, while not excluding it. A precise definition may not explicitly include a number of phenomena of potential interest to communication scholars, while being consistent with less inclusive definitions often used in the field of Communications. Unlike some other definitions, our model suggests that a wide range of phenomena can be viewed as part of a communicative system, but are not necessarily part of communication. For example, given the characteristics of communication described above, this page does not communicate with the reader, but we might say that the author is communicating with the reader. Characteristics of communication, such as intention, aren't included directly in the proposed definition; it isn't excluded, but it isn't explicitly included either. The definition discussed here is more inclusive than most other definitions, while at the same time having more rigor than most. This increases our understanding of communication, and can lead to a more stable foundation for the art and science underlying the information and communication professions, including librarianship.