Section 2. A person reaches through a program's interface to manipulate the domain model. Although the interface is itself a program (an interface model and graphical machinery), its purpose is to enable the direct manipulation of the domain model as transparently as possible.
The user interface is programmed to create the illusion of control in the mind of the user. To this end it must provide sufficient clues of the model's state so that sensible operation is the norm. These patterns offer the required feedback.
Patterns
Echo Back values as they are understood by models.
Visible Implication in context before inputs are saved.
Deferred Validation until input is meaningfully complete.
Instant Projection of the consequences of any publication.
Hypothetical Publication released in a controlled way.
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