Expressions
===========

Expressions in DCWorkflow are TALES expressions. They are used as access
guards and for the setting variable values.

[**Note:** I haven't figured out what all these contexts actually are
and what you can use them for. Explanations are is welcome!]

Some of the contexts have slightly different meanings from what is provided
for expressions in page templates:

* 'here' -- The content object (rather than the workflow object)
* 'container' -- The content object's container

Several other contexts are also provided:

* 'state_change' -- A special object containing information about the state
  change (see below)

* 'transition' -- The transition object being executed

* 'status' -- The former status 'workflow' -- The workflow definition object

* 'scripts' -- The scripts in the workflow definition object

'state_change' objects provide the following attributes, some of which
are duplicates of the above information:

* 'status' is a mapping containing the workflow status. This includes all the
  variables defined in the variable tab with "store in state" checked.

* 'object' is the object being modified by workflow.(Same as the 'here'
  variable above.)

* 'workflow' is the workflow definition object. (Same as the 'workflow'
  variable above.)

* transition' is the transition object being executed. (Same as the
  'transition' variable above.)

* 'old_state' is the former state object. The name of the former state, for
  example "published", is available as 'old_state.getId()'. (Note that
  DCWorkflow defines 'state' and 'status' as different entities; the name of
  the current 'state' is stored in the 'status'. The word clash is unfortunate;
  patches welcome.)

* 'new_state' is the destination state object. Use 'new_state.getId()' to
  access the new state name.

*  'kwargs' is the keyword arguments passed to the doActionFor() method.

* 'getHistory()', a method that returns a copy of the object's workflow
  history.

* 'getPortal()', which returns the root of the portal.

* 'ObjectDeleted' and 'ObjectMoved', exceptions that can be raised by scripts
  to indicate to the workflow that an object has been moved or deleted.

* 'getDateTime' is a method that returns the DateTime of the transition.