= Glossary

action ::
  Code to be executed in order to perform a task.  Actions in a Rakefile are
  specified in a code block. (Usually delimited by +do+/+end+ pairs.)

execute ::
  When a task is executed, all of its actions are performed in the order they
  were defined.  Note that, unlike <tt>invoke</tt>, <tt>execute</tt> always
  executes the actions (without invoking or executing the prerequisites).

file task (Rake::FileTask) ::
  A file task is a task whose purpose is to create a file (which has the same
  name as the task).  When invoked, a file task will only execute if one or
  more of the following conditions are true.

  1. The associated file does not exist.
  2. A prerequisite has a later time stamp than the existing file.

  Because normal Tasks always have the current time as timestamp, a FileTask
  that has a normal Task prerequisite will always execute.

invoke ::
  When a task is invoked, first we check to see if it has been invoked before.
  If it has been, then nothing else is done.  If this is the first time it has
  been invoked, then we invoke each of its prerequisites.  Finally, we check
  to see if we need to execute the actions of this task by calling
  Rake::Task#needed?.  If the task is needed, we execute its actions.

  NOTE: Prerequisites are still invoked even if the task is not needed.

prerequisites ::
  Every task has a (possibly empty) set of prerequisites.  A prerequisite P to
  Task T is itself a task that must be invoked before Task T.

rule ::
  A rule is a recipe for synthesizing a task when no task is explicitly
  defined.  Rules generally synthesize file tasks.

task (Rake::Task) ::
  The basic unit of work in a Rakefile.  A task has a name, a set of 
  prerequisites, and a list of actions to be performed.