Using MQTT Modules to map ISA 95 Enterprise Structure in a UNS Architecure

How can we use Cirrus Link's Sparkplug MQTT Transmission and MQTT Engine modules along with the common ISA-95 equipment model of Enterprise > Site > Area > Line > Equipment to map the model data into a Unified NameSpace.

Sparkplug Basics

Sparkplug defines a standard format for MQTT message topic paths of:

spBv1.0/group_id/Message Type/edge_node_id/device_id 

Sparkplug defines a standard format for MQTT message payloads of:

{         
  "timestamp": <timestamp>,         
  "metrics": [{                 
    "name": <metric_name>,                 
    "alias": <alias>,                 
    "timestamp": <timestamp>,                 
    "dataType": <datatype>,                 
    "value": <value>
  }],
  "seq": <sequence_number>
}

where the ‘name’ of a metric can be hierarchical to build out proper folder structures for applications consuming the metric values.

For example, a simple Sparkplug™ B payload with a two metrics can be represented in JSON as follows:

{         
  "timestamp": 1486144502122,         
  "metrics": [{                 
    "name": "Metric1",                 
    "alias": 1,                 
    "timestamp": 1479123452194,                 
    "dataType": "String",                 
    "value": "Test"         
  },
  {                 
    "name": "Metric Level 1/Metric Level 2/Metric2",                 
    "alias": 2,                 
    "timestamp": 1479123452056,                 
    "dataType": "String",                 
    "value": "Test"         
  }],         
  "seq": 2
} 

Let's take a look at a couple of examples using MQTT Transmission and MQTT Engine. 

We have configured an MQTT Transmission Transmitter to use the Ignition tag tree at the edge to construct the group_id, edge_id and device_id starting at the folder level Site_1. With this configuration, the topic and payload for a change to Tag 1 will be:

• Topic: spBv1.0/Site 1/DDATA/Area 1/Line 1
  • Payload: {"timestamp":1643823757750,"metrics":[{"name":"Equipment 1/Tag 1","timestamp":1643823756467,"dataType":"Boolean","value":True}],"seq":23}

At MQTT Engine, this hierarchal metric name is parsed and the edge folder structure recreated