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The VEC allows the modeling of hierarchical usage nodes(usage nodes with sub-nodes). A use case scenario is e.g. the head left light unit with the sub-unit’s main beam, low beam and the direction indicator (see figure ##).
The diagram above shows the definiton of sub usage nodes. As you can see there is only one main usage node shown, it is called 'A20'. Furthermore the sub nodes 'A20*1', 'A20*2' and 'A20*3' are defined as well. The following examples shows how to work with just one of the sub nodes in detail but of course there can be even more sub nodes underneath the parent one. In listing 1 you can see the XML representaion of the definition of the parent usage node 'A20' and its child node 'A20*1'.
<Specification xsi:type="vec:UsageNodeSpecification" id="id_usage_node_spec_1"> <Identification>UsageNodeList</Identification> <UsageNodes id="id_usage_node_1"> <Identification>A20</Identification> <Description xsi:type="vec:LocalizedString" id="id_1"> <LanguageCode>En</LanguageCode> <Value>Head Ligth left</Value> </Description> <SubUsageNodes>id_usage_node_2</SubUsageNodes> </UsageNodes> <UsageNodes id="id_usage_node_2"> <Identification>A20*1</Identification> <Description xsi:type="vec:LocalizedString" id="id_2"> <LanguageCode>En</LanguageCode> <Value>Main Beam</Value> </Description> </UsageNodes> [...] </Specification>
Because the physical connection to sub nodes is mostly made through the parent usage node, the sub usage nodes are in general connected via an internal connection. Theses connections are shown in figure ## as red connection lines.
To realize these connections in the VEC a ConnectionSpecification with its content can be used. Underneath the specification a ComponentNode object should be placed for the main UsageNode and also for each sub node. These objects can reference the corresponding UsageNode via the “realizedUsageNode” attribute. Further more, the ComponentNode for “Head Ligth left” references its child nodes. In the next step the structure of the ComponentNodes has to be modeled. As the figure 2 shows, for the parent “Head Ligth left” a single logical abstraction of a connector slot is used to group the three connectable pins. This means the main ComponentNode has got one ComponentConnector underneath it with three ComponentPorts. The child nodes get their structure based on this procedure as well. At least each ComponentPort from the child nodes has to be connected to one of them of the parent. To do so a Connection element underneath the ConnectionSpecification is placed. Each of the three Connections references with its ConnectionEnds the corresponding ComponentPorts.
To manage the connection of a connector to the head light and the assignment of signals to the detail level of each pin, the instance of the connector must reference the ComponentNode of the main UsageNode. In this example a connector X instance with its ConnectorHousingRole references the ComponentNode “Head light left” and its cavities references each one of the ComponentPorts underneath the referenced node. In the diagram in figure 4 you can see the needed elements for the modelling of the “Low light” and a referenced connector to it.