In this concept this atomic addressable item is called a node. Each node is a collection of attributes (value-holders) that have values accessible locally in context of the node. To enable browsing, i.e. to represent information about the internal structure of the nodes graph, nodes are interconnected by references (address-holders of coupled nodes).
NodeClass. In other words, the node is an instance of the selected
NodeClasstypes are predefined, i.e. the Address Space Meta-Model provides a strictly defined and non-extensible set of
NodeClasstypes. Each one is assigned a dedicated function to represent well-defined information at run-time.
NodeClassis a formal description of the node defining the allowed attributes and references. Each node must be an instance of the selected
NodeClasstypes (Figure 1):
View: defines a subset of nodes in the Address Space.
ObjectType: provides definition for objects.
Object: is used to represent systems, system components, real-world objects and software objects.
ReferenceType: is used to define the meaning of the nodes relationship.
DataType: is used to define simple and complex data types of the Variable values.
VariableType: is used to provide type definition for variables.
Variable: is used as real-time process data holders, i.e. it provides a value.
Method: is a lightweight function, whose scope is bounded by an owning object.
NodeClassrepresents a subset of the nodes in the Address Space. The entire Address Space is the default view. Each node in a view may contain only a subset of its references, as defined by the creator of the view. The View instance acts as the root for the nodes in the represented view.
ObjectTypeprovides definition for objects.
Objectinstance are used to represent systems, system components, real-world objects and software objects.
ReferenceTypeare visible in the Address Space. In contrast, a reference instance of this type is an inherent part of a node and no
NodeClassis used to represent reference instances. In other words, any node is a collection of references, so there is no need to instantiate an additional object as reference with the role of a nodes couple.
Variablenode is used to be a holder of the process data – it has a
Valueattribute. To be used as the real-time process state representation, the value of the
Valueattribute must be bound to a real data source, e.g. a sensor or actuator. The
Methodnode represents functions that can be called by the clients connected to the server. In this case the real-time process bindings are responsible for conveying the parameters current values, invoking the represented function and returning the execution result. Both classes are the main building blocks that allow the server to couple the exposed address space` with the current state and behavior of the underlying process.
DataTypeis used to define simple and structured data types. Data types are used to describe the bits pattern of the
VariableTypenodes. Therefore each
VariableTyperefers to an instance of the