Comparison of OPC UA complex data models
From OPC Labs Knowledge Base
OPC UA offers two complex data models. They do not have "official" names, but the historically first one is based on the DataTypeDictionary type, and the second one is based on the DataTypeDefinition type. We will therefore usually refer to them as "DataTypeDictionary model" (or "data type dictionary model"), and "DataTypeDefinition model" (or "data type definition model").
The table below summarizes the main difference between the two models.
| DataTypeDictionary Model | DataTypeDefinition Model | ||
|---|---|---|---|
| OPC UA version | 1.00 and later (deprecated in 1.04 and later, but still available) | 1.04 and later | |
| Described in | OPC UA Specification Part 5 (Information Model) | OPC UA Specification Part 3 (Address Space Model) | |
| Compatible with OPC UA Client-Server | yes | yes | |
| Compatible with OPC UA PubSub | no | yes | |
| OPC Binary Data Type System | XML Schema Data Type System | ||
| How are data types described | using a XML document conforming to OPC Binary XML schema defined by OPC Foundation | using XML Schema (commonly referred to as XSD), defined by W3C | |
| Resulting encoding | Binary | XML | any encoding defined in OPC UA (Binary, XML, JSON) |
| Can refer to data types in other servers | yes | yes (details not specified) | no |
| Data type inheritance | no | no | yes |
| Selectable byte order | yes | no | no |
| Simple data types | yes | as per XML Schema capabilities | yes |
| Opaque data types with bit-sized granularity | yes | no | |
| Enumerated data types | yes | yes | |
| Supported in QuickOPC | Version 2018.1 and later | no | Client-Server, Binary encoding: Version 2020.2 and later |
