Merge pull request #820 from hjoliver/xtrigger-redoc

Redo xtrigger docs, with set xtriggers

Author: hjoliver

src/glossary.rst

@@ -69,9 +69,10 @@ Glossary
       don't get overwritten.
 
    active task
+   active window
       Active tasks are those tasks held in memory to feed
-      the scheduling algorithm. They form the ``n=0`` :term:`n-window`,
-      so are always visible in the GUI.
+      the scheduling algorithm. They form the ``n=0`` or *active*
+      :term:`window<n-window>`, so are always visible in the GUI.
 
       Active tasks include:
 
@@ -1686,6 +1687,16 @@ Glossary
       .. seealso::
          * :ref:`user-guide-reflow`
 
+   child
+   parent
+   parentless
+      The upstream and downstream tasks in a dependency pair may be referred
+      to, respectively, as parent and child tasks. Tasks that have parents are
+      spawned into the :term:`active window` of the workflow as soon as the
+      first of their task prerequisites is satisfied by a parent. Parentless
+      tasks don't have any task prerequisites, so they get spawned automatically
+      out to the :term:`runahead limit`.
+
 
    flow number
       Flow numbers are integers passed down from parent task to child task in

src/user-guide/troubleshooting.rst

@@ -346,8 +346,8 @@ It's waiting for upstream tasks to produce their required outputs:
 
    Such tasks will be reported as having unsatisfied dependencies.
 It's waiting for external events:
-   :ref:`Xtriggers <Section External Triggers>` and
-   :ref:`ext-triggers <Old-Style External Triggers>`
+   :ref:`Xtriggers <user_guide.xtriggers>` and
+   :ref:`ext-triggers <user_guide.ext-triggers>`
    can be used to make tasks wait for events
    external to the workflow, such as the progress of task in other workflows
    or the :ref:`real-world time <Built-in Clock Triggers>`.