4 Use cases
4.1 Relationship to reference value
While reading the value of a variable the user might find out if this value is based on a reference value.
This leads to the requirement:
Establish a relationship to a base value (see 7.1 RelativeValueType)
4.2 Describing relative locations in space
The user wants to express the position of an object in a space with respect to its frame of reference.
This leads to the requirement:
Provision of a VariableType to express localization information for any kind of position and/or orientation along with its frame of reference (see 7.2 SpatialLocationType and example in Annex E)
4.3 Standardized description of relative locations in space
The user wants to use a concrete type with defined mathematics to be interoperable with systems which make use of the same type.
This leads to the requirement:
Provision of a concrete VariableType which provides information for position in cartesian coordinates and orientation in angles (see 7.3 CartesianFrameAngleOrientationType)
Definition of standardized mathematical usage of position and orientation (see Annex B)
4.4 Extension of existing objects with relative spatial information
The user wants to extend existing objects in AddressSpace with relative spatial information.
This leads to the requirement:
Provision of an extensible object (see 6.1 SpatialObjectType), which
is identifiable
describes its own position
supports expressing additional points of interest and their positions
4.5 Finding all objects which have relative spatial information
The user wants to find all objects which have relative spatial information with respect to one common coordinate system.
This leads to the requirements:
Provision of an object (see 6.2 SpatialObjectsListType), which
provides a standard entry point to find all objects which provide relative spatial information with respect to one common coordinate system
is identifiable
defines the origin of the coordinate system
communicates content changes inside this set
4.6 Finding all sets of objects with their respective frame of references
The user wants to find all the sets of objects with their common coordinate systems.
This leads to the requirement:
Provision of an object (see 8.1 RelativeSpatialLocations), which provides a standard entry point to find all object sets with their respective coordinate systems
4.7 Distinction of dynamic or static values represented by localization information
The user wants to identify which values of localization information are static or change while runtime, to reduce communication overhead.
This leads to the requirement:
Values should provide information if the value of a frame is static or changing while runtime
OPC UA Core Spec Part 3 v1.05.1 provides a Constant bit within the Attribute AccessLevelEx of a Variable. See an explanation for use in 7.1 RelativeValueType.
4.8 Usage of RSL concept in aggregating and multi-server scenarios
The user wants to handle the RSL concept in aggregating and multi-server scenarios.
This leads to the requirement:
Coordinate systems must be identifiable
Illustration of relationships of coordinate systems described in connected system