Fixing documentation.

README.md

@@ -293,16 +293,18 @@ each factories from a laucnh file the main function is needed.
 
 An executor can be of a type were the node is expanded before
 execution of the node.  The expansion must be of a type that assigns
-execution units to all the new nodes created in the expansion and the
-expansion must be able to be done before we start the execution of the
-whole TST tree. Also if the node to be expanded is on unit X then all
-non-terminal noded need to have X as execution unit.
-
-There is an tree execution server on all agents that takes a service
-call with the whole JSON tree to expand. The first step in this
-execution is to expand the terminal node that should be executed on
-the agent running the execution tree.  The actual expansion is done in
-the ExecutorFactory class for a node type.
+execution units to all the new nodes created in the expansion. The
+expansion of terminal nodes will be done during execution.  Also if
+the node to be expanded is on unit X then all non-terminal noded need
+to have X as execution unit.
+
+There is an tree execution server on all agents. That node handle the
+execuion of a tree. This node will start by expanding the tree with
+the parts that are executed on the same agent.  Remotely executes
+terminal node will be possibly expanded during execution.  There is no
+longer the concept of a global TST tree which was used in the ROS1
+implementation).The actual expansion is done in the ExecutorFactory
+class for a node type.
 
 Example of how to implement an expandable executor for in-air-goal:
 ```python