Electronic Publishing is an all-encompassing term that means
using computers (instead of hot lead) to set type for
documents.  Although publishing includes a sequence of
processes right through distribution, EP tends to emphasize
document composition through production of a single master copy.

It is helpful to picture a graph with "complexity" along
the X axis and "length" along the Y axis.  Complexity
varies from straight text to footnotes and indexing to
tables to line drawings to gray-scale illustration to
full color.  Length varies from 1 page to 10,000 or more
(better make the Y axis logarithmic!)

Word processing dominates the lower left of the graph
(business letters).  Desktop publishing dominates the lower
right (advertising layout).  Host-based text formatters like
troff, TeX and Scribe dominate the upper-left (phone book).
Proprietary systems have traditionally dominated the upper
right (Sears catalog, encyclopedia); these are being supplanted
by hybrids consisting of pieces from the other segments.

The middle of the graph is fair ground for everyone but is
increasingly the domain of Technical Publication systems like
Interleaf and FrameMaker.