The Command Class

The Command interface is fairly straightforward. It contains a limited set of methods that allow for the basic abstracted functionality necessary to fulfill teir task. Currently, classes that implement Command provide:

• A name() method which returns the string name by which the specific command shoule be invoked.
• A commandSig() method which returns the ``signature'' of the command (i.e. how it should be used.
• A help() method which returns some textual information on the intent and usage of the command.
• And a fulfill() method which takes the arguments as parsed by the HsCommandAPI and either processes them or returns an error.

Haystack currently supports the following commands:

• AttachCommand (usage: attach [forward | back] HaystackID1 HaystackID2, returns: boolean) Attach allows us to connect two objects (with IDs HaystackID1 and HaystackID2 respectively). The forward/back relationship indicates the direction we want the link to take (i.e. object1®object2 or object1¬objec2).
• CreateCommand (usage: create type_of_new_object, returns: HaystackID) This command allows us to create new objects of type type_of_new_object. On success it returns the ID for the new object. (Example: create haystack.object.bale.HaystackDocument).
• SetCommand (usage: set HaystackID value_to_set, returns: boolean), this command allows you to set the values of any Needle (indicated by HaystackID) to some value (specifically, value_to_set). It returns 1 on success, 0 on failure.
• TerminateCommand (usage: terminate, returns: boolean) This command causes the HaystackRootServer to shut down. This is a ``clean'' shutdown which calls the close() function on all services gets called.
• ViewCommand (usage: view HaystackID1, returns: string) View returns the string representation of the Straw with the given HaystackID.