= Glossary
[<b>action</b>]
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.
[<b>execute</b>]
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).
[<b>file task</b> (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.
[<b>invoke</b>]
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 its 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
<tt>needed?</tt>. Finally, if the task is needed, we execute
its actions.
NOTE: Currently prerequisites are invoked even if the task is
not needed. This may change in the future.
[<b>prerequisites</b>]
Every task has a set (possiblity empty) of prerequisites. A
prerequisite P to Task T is itself a task that must be invoked
before Task T.
[<b>rule</b>]
A rule is a recipe for synthesizing a task when no task is
explicitly defined. Rules generally synthesize file tasks.
[<b>task</b> (Task)]
Basic unit of work in a rakefile. A task has a name, a set of
prerequisites and a list of actions to be performed.