Connectivity Framework Annex B : Assessment Template : OPC-UA
B . 6.4 Functional Viewpoint B . 6.4.1 Core Framework Layer Functions
Data Resource Model
( Section 4.1.1 )
ID & Addressing ( Section 4.1.2 )
Data Type System ( Section 4.1.3 )
Data Resource Lifecycle ( CRUD ) ( Section 4.1.4 )
State Management ( Section 4.1.5 )
Publish-Subscribe ( Section 4.1.6 )
Request-Reply ( Section 4.1.7 )
Discovery ( Section 4.1.8 )
Exception Handling ( Section 4.1.9 )
Data Quality of Service ( QoS ) ( Section 4.1.10 )
Does it provide a data resource model ? Summarize the salient aspects .
OPC-UA resources are called nodes . They can be individually addressed using a NodeId . Nodes contain data-elements , operations and references to other nodes .
Does it provide a way to identifying and addressing data objects ? Summarize the identification and addressing scheme .
OPC-UA nodes have a unique identifier within a server , called the NodeId .
Addressing a node also requires addressing the OPC-UA server using its network IP address and port , plus the NodeId . Does it provide a data type system ? Summarize the salient aspects .
OPC-UA defines a full data type system . Data-variables within nodes can be of simple or complex ( structured ) data types .
Does it provide a means of managing a data object ’ s lifecycle ? Summarize the salient aspects .
There is no pre-defined resource lifecycle in OPC-UA . However , applications can define their own lifecycles and operations to control the resources .
Does it provide a means to manage the recent history of data objects ? Summarize the salient aspects .
The variables within each node constitute the state of the Node .
Each OPC-UA server manages its own state that is accessible via Query and Browsing services . They cache the last value of every variable they contain . Those can be queried using the Query service .
There is also a full set of historical data access services defined .
Does it provide a means to publish and subscribe the state of data objects ? Summarize the salient aspects .
Plans are underway to include publish-subscribe data exchange . Prototypes are already in field-test .
Does it provide a means to request the state of data objects ? Summarize the salient aspects .
Yes , this is the core primary communication pattern in OPC-UA . Does it provide a means to discover the data objects ? Summarize the salient aspects .
OPC-UA servers can implement a discovery service allowing client applications to discover the nodes they contain .
An OPC-UA server may provide a global registration and discovery service , allowing discovery of all the OPC-UA servers in a system .
Does it provide a means to handle exceptions when quality of service or connectivity violations happen ? Summarize the salient aspects .
Exceptions are supported and communicated via events and alarms .
Does it support data QoS ? Summarize the scope and coverage . Highlight the salient aspects .
OPC-UA offers limited quality of service options beyond the ability to specify an update frequency for the monitored data . There are many QoS features built into the services of OPC-UA . The services are purpose built to provide appropriate QoS .
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