The comparison that generates redline markup in Rational® DOORS® is made on a word by word basis between
two static pieces of text. A longest common subsequence algorithm
is used. Rational DOORS does not save information
about individual keystrokes, so the redline markup might not reflect
the sequence of changes performed by the user.
For example, if Rational DOORS compares ship
wreck to shipwreck, the redline
markup shows ship as deleted, wreck as
deleted and shipwreck as inserted.
Rational DOORS uses word level analysis rather than
character level analysis for performance reasons.