It seems to be the case that our biggest problem is separating CS from related disciplines to some extent. I think this can be best achieved by analogy to fields people have more intuition for.
I have attempted to create such a table:
[source]
Of course, such a table would have to be decorated with appropriated disclaimers: "This is no attempt at defining either notion rigorously; it is only a rough analogy to relate to general knowledge. The same person can perform more than one role. Some tasks may be associated with more than one role." and so on.
What do you think, can an analogy clarify what we have trouble defining clearly?
Do you have other/better analogies?