  This paper develops a computational model of paraphrase under which text
modification is carried out reluctantly; that is, there are external
constraints, such as length or readability, on an otherwise ideal text, and
modifications to the text are necessary to ensure conformance to these
constraints. This problem is analogous to a mathematical optimisation problem:
the textual constraints can be described as a set of constraint equations, and
the requirement for minimal change to the text can be expressed as a function
to be minimised; so techniques from this domain can be used to solve the
problem.
  The work is done as part of a computational paraphrase system using the XTAG
system as a base. The paper will present a theoretical computational framework
for working within the Reluctant Paraphrase paradigm: three types of textual
constraints are specified, effects of paraphrase on text are described, and a
model incorporating mathematical optimisation techniques is outlined.
