An Organizational Network MapIn 1996 The Advisory Board Company published a report that included a section (pdf) on organizational network mapping. The latter provides a nice visual example of how a company's formal and informal organization can diverge.
First, the formal organization, with five work units, is shown below. The organizational network map captures how the individuals in these work units interact internally and exernally:
And now, here is the informal organization. There are three communities of practice, whose membership is determined by the types and frequency of communication between various pairs of employees:
You can review an outline of the steps for producing an organizational network in this earlier post.