Names of design patterns appear in small capitals: e.g., ADAPTER. Page numbers in bold indicate the definition of a term. Numbers in italics indicate a diagram for the term. Letters after a diagram's page number indicate the kind of diagram: a "c" denotes a class diagram, an "i" denotes an interaction diagram, and an "o" denotes an object diagram. For example, 88co means that a class and object diagram appears on page 88.

## U

undo/redo 59-60, 62-64, 235, 238, 283, 287
  avoiding error accumulation during 239
Unidraw
  use of ADAPTER 143
  use of CHAIN OF RESPONSIBILITY 232
  use of COMMAND 232, 242
  use of FACTORY METHOD 111
  use of ITERATOR 270
  use of MEDIATOR 282
  use of MEMENTO 289
  use of OBSERVER 303
  use of PROTOTYPE 126
  use of STATE 313
UnsharedConcreteFlyweight
  participant of FLYWEIGHT 199
updates
  encapsulating complex 299
  limiting unexpected 296
  protocol for in OBSERVER 296
  triggering 297