The Attributes of an IOD describe the properties of a Real-World Object Instance. Related Attributes are grouped into Modules that represents a higher level of semantics documented in the Module Specifications found in PS3.3.

Attributes are encoded as Data Elements using the rules, the Value Representation and the Value Multiplicity concepts specified in PS3.5. For specific Data Elements, the Value Representation and Value Multiplicity of Data Elements are specified in the Data Dictionary in PS3.6.