Update documentation to deal with item_array and sub_item_array

doc/userdoc.org

@@ -2831,32 +2831,35 @@ The information produced concerns
 
 This type is used to designate kinds of items (cell, face, edge or node).
 
-***** ~item_value~
+***** ~item_value~ and ~item_array~
 
-The type ~item_value~ is an abstract type use to designate arrays of
-values defined on the entities of a ~mesh~. Actually, these values are
-not associated to the mesh itself but to the *connectivity*. The values
-on the entities can be of type ~B~, ~N~, ~Z~, ~R~, ~R^1~, ~R^2~, ~R^3~, ~R^1x1~, ~R^2x2~
-and ~R^3x3~. Entities themselves can be cells, faces, edges or nodes.
+The types ~item_value~ and ~item_array~ are abstract types use to
+designate values or arrays of values defined on each entities of a
+~mesh~. Actually, these set of values (or arrays) are not associated to
+the mesh itself but to the *connectivity*. The values on the entities
+can be of type ~B~, ~N~, ~Z~, ~R~, ~R^1~, ~R^2~, ~R^3~, ~R^1x1~, ~R^2x2~ and
+~R^3x3~. Entities themselves can be cells, faces, edges or nodes.
 
 These variables are used to pass data from one function to another.
 
 #+BEGIN_warning
-By now, no mathematical operation is defined on ~item_value~ variables.
+By now, no mathematical operation is defined on ~item_value~ or
+~item_array~ variables.
 #+END_warning
 
 Moreover, ~item_value~ variables can be post processed. Observe that
 edge or face values cannot be post processed since neither ~VTK~ nor
-~Gnuplot~ can handle these data.
+~Gnuplot~ can handle these data. Also ~item_raray~ can only be post
+processed if array per item contain scalar data ( ~B~, ~N~, ~Z~, ~R~).
 
-***** ~sub_item_value~
+***** ~sub_item_value~ and ~sub_item_arrays~
 
-This abstract type handles values defined on the sub items of the
-items of a ~mesh~. Similarly these values are attached to a *connectivity*
-and not to a mesh. The values associated to the sub items can be of
-type ~B~, ~N~, ~Z~, ~R~, ~R^1~, ~R^2~, ~R^3~, ~R^1x1~, ~R^2x2~ or ~R^3x3~. An example of
-~sub_item_value~ is the $\mathbf{C}_{jr}$ vectors which are defined at each
-node of each cell.
+These abstract type handles values or arrays defined on the sub items
+of the items of a ~mesh~. Similarly these sets of values or arrays are
+attached to a *connectivity* and not to a mesh. The values associated to
+the sub items can be of type ~B~, ~N~, ~Z~, ~R~, ~R^1~, ~R^2~, ~R^3~, ~R^1x1~, ~R^2x2~
+or ~R^3x3~. An example of ~sub_item_value~ is the $\mathbf{C}_{jr}$ vectors
+which are defined at each node of each cell.
 
 These variables are used to pass data from one function to
 another. They cannot be post processed.