Decompositions and models for Hilbert-space operators have been very
active research topics in operator theory over the past three decades.
This book is intended as an introduction to this crucial part of
operator theory, providing for the student a unified access, from an
abstract point of view, to an active research field. It focuses on
decompositions and models as if they were the main characters in a plot,
chosen from a myriad of equally important characters, and highlighted
for their illustrative attributes. It has been written for an audience
composed mainly of graduate students taking operator theory either as
their major or as a support for applications in mathematics or in one of
the sciences. The approach is elementary in the sense that all proofs
use only standard results of single operator theory. However, a number
of questions posed throughout the text provide the flavor of a research
monograph in that they lead the reader to investigate some open
problems, a number of them classical. This approach will help the reader
to visualize, even if only partially, the frontiers of a few directions
in which operator theory has been developing. Although the material is
mainly drawn from a variety of sources, there are some original
contributions in the form of new intermediate results and simplified
proofs.