Procedure Covering({X,Tc}, y):
mid ←  :
result ←  :
Z = {z ∈ X | (z (=, . . .) ∈ T };
s E (Z) do if | s | ≥ 2 and the graph ⟨ X , TE ⟩ obtained by deleting the "=" temporal relation between the node y and each of the nodes in s is inconsistent then mid ← mid   {s};
s E mid do if   t E mid. t C s then result ←— result
{ s } ;
return result.

igure rocedure which computes a covering.

Note that ef - makes explicit all the possible chains of features by reducing ea nontemporal concept to a con unction of atomic concepts, feature selections restricted to atomic concepts and feature agreements   i.e., each    is a feature term expression    molka, The normalization proceeds by discovering all the possibles interactions between nodes with the intention of making explicit all the implicit information. A crucial temporal interaction occurs when a node is always coincident with a set of nodes in every possible interpretation of the temporal network.

Definition 6.2 (Covering) Given a temporal constraint network        , let and V 
V
0, V
then   is called uncovered, otherwise   is said coveral by ¯.

Proposition 6.3 (Covering procedure) Given a temporal constraint network minimal form (see, e.g., (van Beek & Manchak, 1996)) and a node                  then the procedure described in Figure 12 returns all the possible coverings for   with size ≥
The idea behind the covering is that whenever a set of nodes p is a covering for the dis unctive concept expression 2 see 2 should be con unctively added to the concept expression    Actually, since in TL-F concept dis unction is not allowed it will be sufficient to add to the node the Last Commom Subsumer LCS of as defined below.

Definition 6.4 (LCS) Let n           be F concept expressions. Then, the concept and there is no    such that LCS
n is such that:

n iven a concept in existential form, the temporal completion of the constraint network is computed as described below. Definition 6.5 (Completed existential form)  The temporal completion of a concept in existential form   the Completed Existential Form, CEF   is obtained by sequentially applying the following steps: