Adding extension for OPC UA

cloudevents/extensions/README.md

@@ -44,6 +44,7 @@ for more information.
 - [Dataref (Claim Check Pattern)](dataref.md)
 - [Distributed Tracing](distributed-tracing.md)
 - [Expiry Time](expirytime.md)
+- [OPC UA](opcua.md)
 - [Partitioning](partitioning.md)
 - [Recorded Time](recordedtime.md)
 - [Sampling](sampledrate.md)

cloudevents/extensions/opcua.md

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+# OPC UA
+
+This extension defines the mapping of [OPC UA](https://reference.opcfoundation.org/Core/Part1/v105/docs/)
+[PubSub](https://reference.opcfoundation.org/Core/Part14/v105/docs/) dataset to
+CloudEvents to allow seamless routing of OPC UA dataset messages via different
+protocols, it therefore provides a recommendation to map known REQUIRED and
+OPTIONAL attributes using other extensions as well as defines its own extension
+attributes.
+
+## Notational Conventions
+
+As with the main [CloudEvents specification](../spec.md), the key words "MUST",
+"MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
+"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as
+described in [RFC 2119](https://tools.ietf.org/html/rfc2119).
+
+However, the scope of these key words is limited to when this extension is used.
+For example, an attribute being marked as "REQUIRED" does not mean it needs to
+be in all CloudEvents, rather it needs to be included only when this extension
+is being used.
+
+## Mapping of REQUIRED Attributes
+
+### id
+
+MUST map to [Network Message
+Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.3#Table163)
+field `MessageId`.
+
+### source
+
+MUST either map to [Application
+Description](https://reference.opcfoundation.org/Core/Part4/v104/docs/7.1) field
+`applicationUri` of the OPC UA server or to a customer configured identifier
+like a unified namespace path.
+
+### type
+
+MUST map to [Data Set Message Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.4#Table164)
+field `MessageType`.
+
+## Mapping of OPTIONAL Attributes
+
+### datacontenttype
+
+MUST be `application/json` for OPC UA PubSub JSON payload and MAY be appended with
+`+gzip` when the payload is gzip compressed.
+
+### dataschema
+
+OPC UA provides type information as part of PubSub metadata messages, for non
+OPC UA consumers or when different payload encoding like Avro is used, it is
+REQUIRED to provide schema information (based on metadata information) in a
+separate format like [JSON schema](https://json-schema.org/specification) or
+[Avro schema](https://avro.apache.org/docs/1.11.1/specification/) or others. For
+those cases the attribute references the schema and is used for versioning.
+
+### subject
+
+For metadata, event and data messages (type one of `ua-metadata`, `ua-keyframe`,
+`ua-deltaframe`, `ua-event`), `subject` MUST map to either [Data Set Message
+Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.4#Table164)
+field `DataSetWriterId` or `DataSetWriterName`.
+
+For event messages (type equals to `ua-event`) `subject` MUST be appended with 
+"/" and [Base Event Type](https://reference.opcfoundation.org/Core/Part5/v104/docs/6.4.2)
+field `EventId`. 
+
+### time
+
+MUST map to [Data Set Message
+Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.4#Table164)
+field `Timestamp`.
+
+## Mapping for other extensions
+
+The following well-known extensions attributes MUST be used for data messages and
+event messages (type one of `ua-keyframe`, `ua-deltaframe`, `ua-event`).
+
+### sequence
+
+Attribute as defined by [sequence extensions](./sequence.md) MUST map to [Data
+Set Message Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.4#Table164)
+field `SequenceNumber`.
+
+### traceparent
+
+Attribute as defined by [distributed-tracing extension](./distributed-tracing.md)
+to allow tracing from event publisher towards consumer.
+
+### tracestate
+
+Attribute as defined by [distributed-tracing extension](./distributed-tracing.md)
+MAY be used to allow tracing from event publisher towards consumer.
+
+### recordedtime
+
+Attribute as defined by [recordedtime extension](./recordedtime.md) to
+determine the latency between event publisher towards consumer.
+
+## Attributes
+
+### opcuametadatamajorversion
+
+- Type: `Integer`
+- Description: Links dataset message to the current version of the metadata.
+Contains value from `MajorVersion` of [Data Set Message Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.4#Table164) field `MetaDataVersion`. 
+- Constraints
+  - OPTIONAL but MUST NOT be present if `dataschema` is used
+
+### opcuametadataminorversion
+
+- Type: `Integer`
+- Description: Links dataset message to the current version of the metadata.
+Contains value from `MinorVersion` of [Data Set Message
+Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.4#Table164)
+field `MetaDataVersion`.
+- Constraints
+  - OPTIONAL but MUST NOT be present if `dataschema` is used
+
+### opcuastatus
+
+- Type: `Integer`
+- Description: Defines the overall status of the data set message, maps to 
+[Data Set Message Header](https://reference.opcfoundation.org/Core/Part14/v105/docs/7.2.5.4#Table164) field `Status`.
+- Constraints
+  - OPTIONAL
+  - REQUIRED if status is not _Good_
+  - MAY be omitted if status is _Good_
+
+## General Constraints
+
+- OPC UA messages MUST use `binary-mode` of CloudEvents.
+- OPC UA PubSub JSON messages MUST be encoded using non-reversible encoding as
+the decoding information is contained in metadata messages or by schema
+referenced via `dataschema` attribute.
+- Payload of OPC UA PubSub JSON messages MUST NOT contain Network Message Header
+and Data Set Header as that information is mapped into CloudEvents attributes.
+- OPC UA PubSub JSON messages MUST contain exactly one dataset message.
+
+## Examples
+
+### Metadata message
+
+The metadata message helps Cloud applications to understand the semantics and 
+structure of dataset messages.
+
+```text
+------------------ PUBLISH -------------------
+
+Topic Name: opcua/json/DataSetMetaData/publisher-on-ot-edge
+Content Type: application/json; charset=utf-8
+
+------------- User Properties ----------------
+
+specversion: 1.0
+type: ua-metadata
+time: 2024-03-28T21:56:24Z
+id: 1234-1234-1234
+source: urn:factory:aggregationserver:opcua
+datacontenttype: application/json; charset=utf-8
+subject: energy-consumption-asset
+       .... further attributes ...
+
+------------------ payload -------------------
+
+{
+    ... application data (OPC UA PubSub metadata) ...
+    "ConfigurationVersion": {
+      "MajorVersion": 672338910,
+      "MinorVersion": 672341762
+    }
+    ...
+}
+
+-----------------------------------------------
+```
+
+### Telemetry message 
+
+The telemetry or data messages contain values of all OPC UA nodes that had 
+changed in a given period of time (`ua-deltaframe`) or contain values for all 
+OPC UA nodes that were monitored (`ua-keyframe`). 
+The complete list of monitored OPC UA nodes as well as the related type 
+information are defined in the metadata message. The attributes 
+`opcuametadatamajorversion` and `opcuametadataminorversion` are used to
+reference the correct metadata message. The `ua-deltaframe` messages will be 
+used for hot and/or cold path processing and `ua-keyframe` messages can 
+additional be used to update last-known-value tables.
+
+
+```text
+------------------ PUBLISH -------------------
+
+Topic Name: opcua/json/DataSetMessage/publisher-on-ot-edge
+Content Type: application/json; charset=utf-8
+
+------------- User Properties ----------------
+
+specversion: 1.0
+type: ua-deltaframe
+time: 2024-03-28T21:56:42Z
+id: 1235-1235-1235
+source: urn:factory:aggregationserver:opcua
+datacontenttype: application/json; charset=utf-8
+subject: energy-consumption-asset
+sequence: 7
+traceparent: 4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00000011
+recordedtime: 2024-03-28T21:56:43Z
+opcuametadatamajorversion: 672338910
+opcuametadataminorversion: 672341762
+       .... further attributes ...
+
+------------------ payload -------------------
+
+{
+    ... application data 
+        (OPC UA PubSub JSON single dataset Message)...
+}
+
+-----------------------------------------------
+```
+
+#### OPC UA PubSub JSON single dataset Message
+
+Using CloudEvents and model the OPC UA PubSub header information as CloudEvent 
+attributes enables integration into various system (independent from used 
+protocols) and simplifies the payload structure. 
+
+```text
+{
+    "IsRunning": {
+        "Value": true,
+        "SourceTimestamp": "2024-03-29T07:31:19.555Z"
+    },
+    "EnergyConsumption": {
+        "Value": 31
+        "SourceTimestamp": "2024-03-29T07:31:37.546Z",
+        "StatusCode": {
+            "Code":1073741824,
+            "Symbol":"Uncertain"
+        }
+    },
+    "EnergyPeak": {
+        "Value": 54
+        "SourceTimestamp": "2024-03-29T07:31:06.978Z"
+    },
+    "EnergyLow": {
+        "Value": 22
+        "SourceTimestamp": "2024-03-29T07:31:17.582Z"
+    }
+}
+
+```
+
+### Event message
+
+The event message will contain a single event and the identifier of this event is
+added to the `subject` to allow routing it into different systems without parsing 
+the payload. Events are routed for example in systems like Manufacturing Execution 
+Systems (MES), Supervisory Control and Data Acquisition systems (SCADA), 
+Alerting Systems or Operation Technology Operator Terminals (HMI Clients) and 
+also in hot and/or cold path processing. The attributes 
+`opcuametadatamajorversion` and `opcuametadataminorversion` are used to
+reference the correct metadata message.
+
+```text
+------------------ PUBLISH -------------------
+
+Topic Name: opcua/json/DataSetMessage/publisher-on-ot-edge
+Content Type: application/json; charset=utf-8
+
+------------- User Properties ----------------
+
+specversion: 1.0
+type: ua-event
+time: 2024-03-28T21:57:01Z
+id: 1236-1237-1238
+source: urn:factory:aggregationserver:opcua
+datacontenttype: application/json; charset=utf-8
+subject: energy-consumption-asset/444321
+sequence: 18
+traceparent: caffef3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00000011
+recordedtime: 2024-03-28T21:57:01Z
+opcuametadatamajorversion: 672338910
+opcuametadataminorversion: 672341762
+       .... further attributes ...
+
+------------------ payload -------------------
+
+{
+    ... application data 
+        (OPC UA PubSub JSON Single Event Message)...
+}
+
+-----------------------------------------------
+```
+
+### Telemetry message with different Encoding  
+
+One major benefit of CloudEvents for OPC UA is that it is possible to support 
+other encoding and external schema, while keeping the same OPC UA information for 
+routing.
+
+The example below uses Avro binary encoded payload, with the corresponding schema 
+referenced by `dataschema`. The `source` will be defined by an customer defined 
+hierarchical path.
+
+```text
+------------------ PUBLISH -------------------
+
+Topic Name: bottling-company/amsterdam/FillingArea1/FillingLine9/Cell1/Conveyor
+Content Type: application/avro
+
+------------- User Properties ----------------
+
+specversion: 1.0
+type: ua-keyframe
+time: 2024-03-28T23:59:59Z
+id: 6235-7235-8235
+source: bottling-company/amsterdam/FillingArea1/FillingLine9/Cell1/Conveyor
+datacontenttype: application/avro
+subject: energy-consumption-asset
+dataschema: http://example.com/schemas/energy-consumption-asset/v1.8
+sequence: 3141
+traceparent: 22222f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00000011
+recordedtime: 2024-03-28T23:59:59Z
+       .... further attributes ...
+
+------------------ payload -------------------
+
+    ... application data 
+        (OPC UA PubSub Single DataSet Message as AVRO binary)...
+
+-----------------------------------------------
+```

cloudevents/languages/he/extensions/opcua.md

@@ -0,0 +1,2 @@
+# OPC UA
+מסמך זה טרם תורגם. בבקשה תשתמשו [בגרסה האנגלית של המסמך](../../../extensions/opcua.md) לבינתיים.

cloudevents/languages/zh-CN/extensions/opcua.md

@@ -0,0 +1,6 @@
+# OPC UA
+
+本文档尚未被翻译，请先阅读英文[原版文档](../../../extensions/opcua.md) 。
+
+如果您迫切地需要此文档的中文翻译，请[提交一个issue](https://github.com/cloudevents/spec/issues) ，
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