SAE AS6969, Revision A, October 2020 - (R) Data Dictionary for Quantities Used in Cyber Physical Systems

This data dictionary provides definitions for quantities, measurement units, reference systems, measurands, measurements and quantity modalities commonly used in the command and control of cyber physical systems. A cyber physical system is an engineered system that is built from, and depends upon, the seamless integration of computational algorithms and physical components. Cyber physical systems are often interconnected via data links and networks. The term encompasses intelligent vehicles and devices that operate in any environment, including robotic and autonomous systems. 

Purpose 

This data dictionary may be used in the development and cross-comparison of data models and in general system and software engineering. The data dictionary can also be extended by users through the creation of quantity domains. 

Considerable interoperability can be achieved between different data models when these models reference the same definition URIs provided in this dictionary or its extensions. This includes data models based on different modeling languages and annotated with different spoken languages. 

Limitations 

This data dictionary is concerned with state data exchanged during the operational activities of cyber physical systems. It is not concerned with system design specifications or parameters. This data dictionary is not concerned with the datatypes or classes in a data model. 

Viewpoint 

In a data model, a class or datatype may own properties. A quantity is a property whose value has a numerical magnitude. For example, the class Aircraft may own the property of airspeed whose basic quantity is velocity. In this example, the measurand specification is Aircraft:: airspeed: Velocity. 

Specific measurands may be defined in extensions to this standard. These extensions are called quantity domains. This core standard defines basic quantities together with their mathematical structures. For example, the basic quantity of velocity may be expressed in different vector spaces and measurement units. This core standard also defines the general definitions and structure of a quantity domain. 

In a cyber physical system, a quantity value may have multiple modalities. A categorical value is the observable state of the measurand. Other modalities can express possible or necessary values, permissible or obligatory values, the uncertainty of a value, and so on. These modalities are defined in this core standard and would be applied in specific data models that reference this data dictionary.