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A node may represent a real world object such as a location or a piece of equipment. A node may also represent a schema item
such as a type or property. Nodes correspond to “branches? in the IOPCBrowseServerAddressSpace or IOPCEventAreaBrowser interfaces.
Nodes correspond to Resources in the RDF model and the DAF interface. Each node has a universal identity given by its ResourceID.
The ResourceID of a node is the same in all views provided by a DAIS server. DAIS servers may be coordinated with DAF servers
so that a node has the same ResourceID as the corresponding resource. Each node has zero or more child(s). A child may be
another node or any other type of object (for example, data access items or alarms & event sources). Each node has a type.
The type determines what other types of child objects a node has.
Nodes are arranged in a strict hierarchy for naming purposes. A DAIS server may provide more than one such hierarchy, each
is called a view. (The view is selected when the session is initiated.) Within a view, each node, except for the root node,
has a single parent node, a label that is unique among all nodes with the same parent, and a unique pathname. A node’s pathname
is a string that contains its label and the pathname of its parent. The pathname must be a valid URI, but apart from that
the syntax of pathnames is implementation dependent.
The Node IDL defines a main interface DAIS::Node::IHome for browsing among the hierarchically structured nodes. Nodes are
described by DAIS::Node::Description struct.
Figure 3-2 DAIS node IDL in UML