update description and remove reference to Progress element

xsd/siri_model/siri_situationActions.xsd

@@ -601,9 +601,10 @@ Rail transport, Roads and road transport
 					</xsd:element>
 					<xsd:element name="ActionIsClosing" type="xsd:boolean" default="false" minOccurs="0">
 						<xsd:annotation>
-							<xsd:documentation>ActionIsClosing 'true' is identical to Progress 'closing' but only for this individual Action. 
-If an Action is about to close, passengers are informed about normalisation. Usually ActionIsClosing 'true' results in the display of a specific symbol understood as "traffic is normalizing" or "restrictions are lifted". 
-Closing is also related to the display priority, i.e., Actions with ActionIsClosing are only to be displayed by consuming systems with enough space to spare.</xsd:documentation>
+							<xsd:documentation>ActionIsClosing 'true' signals to the consuming system that the corresponding TextualContent informs passengers about a normalisation. 
+Consequently, the consuming system will display a specific symbol, understood by passengers as "traffic is normalizing" or "restrictions are lifted", in combination with the TextualContent of this action. 
+Actions corresponding to a normalisation of traffic typically have a lower display priority than other actions, i.e., should be displayed only if enough space is available.
+By default, an action does not correspond to a normalisation, i.e., has ActionIsClosing 'false'.</xsd:documentation>
 						</xsd:annotation>
 					</xsd:element>
 					<xsd:element name="TextualContent" type="TextualContentStructure" maxOccurs="unbounded">