Version: 2.0

UNS (Unified Namespace) Nodes

Overview

The Unified Namespace (UNS) is MaestroHub's central data fabric that organizes all operational data into a hierarchical topic tree following the ISA-95 model (enterprise / site / area / line / cell). UNS nodes allow pipelines to interact with this namespace — publishing live data, retrieving historical records, discovering topics, and triggering workflows when new data arrives.

Unlike industrial or database connector nodes, UNS nodes do not require an external connection profile. They communicate directly with the built-in UNS Manager service, making them zero-configuration from a connectivity standpoint.

Topic Structure

Every UNS topic path is prefixed with a version string that scopes the namespace schema. The current default version is mHv1.0.

mHv1.0/enterprise/site/area/machine/temperature
└─────┘ └──────────────────────────────────────┘
version              topic path

The system automatically prepends the version prefix if it is not already present in the configured topic. In the UI, a version selector dropdown lets you choose the active version while you type the topic path.

Available Nodes

Node	Type ID	Category	Purpose
UNS Subscribe Trigger	`trigger.uns.subscribe`	Trigger	Starts a pipeline when data is published to matching UNS topics
UNS Publish	`system.uns.publish`	UNS	Publishes data to a UNS topic
UNS Fetch Data	`system.uns.fetchdata`	UNS	Retrieves recent data from a UNS topic
UNS Search Nodes	`system.uns.searchnodes`	UNS	Searches the namespace for topics by keyword

UNS Topic Selector

The UNS Publish and UNS Fetch Data nodes share a specialized UNS Topic Selector control for configuring the target topic. Understanding this component helps you work with any UNS node that requires a topic.

How It Works

Version Selector — a dropdown on the left side of the field displays the available namespace versions (fetched from the backend). The default version (mHv1.0) is pre-selected.
Topic Path Input — a text input where you type the topic path. As you type (minimum 2 characters), the system searches existing topics and shows autocomplete suggestions in a dropdown.
Expression Support — the field accepts pipeline expressions ({{ }} syntax). When an expression is detected, autocomplete is disabled and a live preview evaluates the expression against available upstream data.
Full Topic Preview — below the input, a preview badge shows the complete resolved path including the version prefix (e.g., mHv1.0/enterprise/site/area/machine/temperature).

Expression Preview States

State	Indicator	Meaning
Evaluating	Spinner	Expression is being evaluated.
Success	Green checkmark	Expression resolved successfully; shows the resolved value.
Missing data	Info icon (muted)	Upstream node data not yet available — run upstream nodes first.
Error	Red alert	Syntax error or evaluation failure in the expression.

UNS Publish

UNS Publish Node

Overview

The UNS Publish node writes data to a UNS topic. It is the primary way pipelines push processed results, enriched telemetry, calculated KPIs, or control signals back into the Unified Namespace for other systems and pipelines to consume.

Publishing is synchronous — the node waits for confirmation from the UNS Manager before completing, ensuring reliable delivery.

Node Handles

Handle	Position	Description
Input (`in`)	Left	Receives data from the upstream node.
Output (`out`)	Right	Sends the publish confirmation and metadata to downstream nodes.

Parameters

Field	UI Control	Data Type	Required	Default	Validation	Description
UNS Topic	UNS Topic Selector (version dropdown + path input with autocomplete)	string	Yes	`""`	Must not be empty after expression resolution	Full UNS topic path. The version prefix is auto-prepended if missing. Supports expressions.
Value	Expression Field (multiline textarea with preview)	any	Yes	`""`	Must not be empty or null	Data to publish. Accepts literal values, JSON objects, or expressions that resolve to any type.
Data Source	Expression Field (single-line input with preview)	string	No	`""` (auto-generated)	—	Identifier for the data source. If left empty, defaults to `pipeline:{pipelineName}:{pipelineId}`. Supports expressions.

Settings

Description

A free-text area for documenting the node's purpose.

Execution Settings

Setting	Options	Default	Description
Timeout (seconds)	1–600	Pipeline default	Maximum execution time for this node.
Retry on Timeout	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry if the node times out.
Retry on Fail	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry on failure. When Enabled, reveals Advanced Retry Configuration.
On Error	Pipeline Default / Stop Pipeline / Continue Execution	Pipeline Default	Behavior when the node fails after all retries.

Advanced Retry Configuration (visible when Retry on Fail = Enabled)

Field	Type	Default	Range	Description
Max Attempts	number	3	1–10	Maximum retry attempts.
Initial Delay (ms)	number	1000	100–30,000	Wait before first retry.
Max Delay (ms)	number	120000	1,000–300,000	Upper bound for backoff delay.
Multiplier	number	2.0	1.0–5.0	Exponential backoff multiplier.
Jitter Factor	number	0.1	0–0.5	Random jitter.

Output Data Structure

On successful publish, the node produces:

{
  "published": true,
  "topic": "mHv1.0/enterprise/site/area/machine/temperature",
  "value": { "temperature": 72.5, "unit": "F" },
  "source": "pipeline:Temp-Monitor:abc-123",
  "timestamp": "2026-02-11T14:15:00Z"
}

Field	Type	Description
`published`	boolean	Always `true` on success.
`topic`	string	The full topic path the data was published to (including version prefix).
`value`	any	The value that was published, as resolved from the input expression.
`source`	string	The source identifier used for this publish operation.
`timestamp`	string	ISO 8601 timestamp of when the publish occurred (UTC).

Referencing in Downstream Nodes

{{ $node["UNS Publish"].published }}   → true
{{ $node["UNS Publish"].topic }}       → the full topic path
{{ $node["UNS Publish"].timestamp }}   → when it was published

Validation Rules

Rule	Error Message
Node name is required	"UNS Publish node must have a name"
UNS topic is required	"UNS topic is required"
Value is required	"Value is required"
Topic must resolve to non-empty string	"topic resolved to empty string"

Usage Examples

Publish Transformed Sensor Data

Field	Value
UNS Topic	`mHv1.0/acme-corp/plant-1/assembly/robot-arm/temperature`
Value	`{{ $node["Set"].data }}`
Data Source	(empty — auto-generated)

The pipeline reads a raw sensor value, transforms it with a Set node, and publishes the enriched result back to the UNS.

Publish Aggregated KPIs

Field	Value
UNS Topic	`mHv1.0/acme-corp/plant-1/kpis/oee`
Value	`{"oee": {{ $node["Calculate OEE"].result }}, "shift": "morning", "timestamp": "{{ $execution.startedAt }}"}`
Data Source	`kpi-calculator`

Publishes a calculated OEE metric with context about the shift and execution time.

Dynamic Topic from Trigger Data

Field	Value
UNS Topic	`{{ $trigger._metadata.topic }}/processed`
Value	`{{ $node["Transform"].output }}`
Data Source	(empty)

Appends /processed to the original trigger topic, creating a parallel processed-data topic hierarchy.

UNS Fetch Data

UNS Fetch Data Node

Overview

The UNS Fetch Data node retrieves the most recent data records stored in the UNS for a given topic. It is ideal for building dashboards, performing trend analysis, or feeding historical context into decision-making logic within a pipeline.

Node Handles

Handle	Position	Description
Input (`in`)	Left	Receives data from the upstream node.
Output (`out`)	Right	Sends the fetched records and metadata to downstream nodes.

Parameters

Field	UI Control	Data Type	Required	Default	Validation	Description
UNS Topic	UNS Topic Selector (version dropdown + path input with autocomplete)	string	Yes	`""`	Must not be empty after expression resolution	The topic to fetch data from. Supports expressions.
Limit	Number input	number	No	`10`	1–1,000 (clamped to 1,000 if exceeded)	Number of most recent records to retrieve.

Settings

Description

A free-text area for documenting the node's purpose.

Execution Settings

Setting	Options	Default	Description
Timeout (seconds)	1–600	Pipeline default	Maximum execution time for this node.
Retry on Timeout	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry if the node times out.
Retry on Fail	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry on failure. When Enabled, reveals Advanced Retry Configuration.
On Error	Pipeline Default / Stop Pipeline / Continue Execution	Pipeline Default	Behavior when the node fails after all retries.

Advanced Retry Configuration (visible when Retry on Fail = Enabled)

Field	Type	Default	Range	Description
Max Attempts	number	3	1–10	Maximum retry attempts.
Initial Delay (ms)	number	1000	100–30,000	Wait before first retry.
Max Delay (ms)	number	120000	1,000–300,000	Upper bound for backoff delay.
Multiplier	number	2.0	1.0–5.0	Exponential backoff multiplier.
Jitter Factor	number	0.1	0–0.5	Random jitter.

Output Data Structure

The node returns an envelope containing the fetched records:

{
  "records": [
    {
      "id": "rec-001",
      "topic": "mHv1.0/enterprise/site/area/machine/temperature",
      "value": { "temperature": 72.5, "unit": "F" },
      "source": "pipeline:Temp-Monitor:abc-123",
      "timestamp": "2026-02-11T14:10:00Z",
      "retain": false
    },
    {
      "id": "rec-002",
      "topic": "mHv1.0/enterprise/site/area/machine/temperature",
      "value": { "temperature": 73.1, "unit": "F" },
      "source": "pipeline:Temp-Monitor:abc-123",
      "timestamp": "2026-02-11T14:05:00Z",
      "retain": false
    }
  ],
  "count": 2,
  "topic": "mHv1.0/enterprise/site/area/machine/temperature",
  "fetchMode": "recent"
}

note

The fetchMode field in the output is always "recent". Time-range based fetching is not currently available.

Field	Type	Description
`records`	array	Array of data records matching the query.
`records[].id`	string	Unique record identifier.
`records[].topic`	string	The topic the record belongs to.
`records[].value`	any	The stored data value.
`records[].source`	string	The source that published the record.
`records[].timestamp`	string	ISO 8601 timestamp of when the record was published.
`records[].retain`	boolean	Whether this was a retained message.
`count`	number	Number of records returned.
`topic`	string	The topic that was queried.
`fetchMode`	string	The fetch mode used (currently always `"recent"`).

Referencing in Downstream Nodes

{{ $node["UNS Fetch Data"].records }}        → the full records array
{{ $node["UNS Fetch Data"].records[0].value }}  → the most recent record's value
{{ $node["UNS Fetch Data"].count }}           → number of records returned
{{ $node["UNS Fetch Data"].fetchMode }}       → "recent"

Validation Rules

Rule	Error Message
Node name is required	"UNS Fetch Data node must have a name"
UNS topic is required	"UNS topic is required"
Limit must be between 1 and 1,000	"Limit must be between 1 and 1000"
Topic must resolve to non-empty string	"topic resolved to empty string"

Usage Examples

Fetch Latest 5 Readings

Field	Value
UNS Topic	`mHv1.0/acme-corp/plant-1/assembly/robot-arm/temperature`
Limit	`5`

Downstream usage: {{ $node["UNS Fetch Data"].records }} to iterate over the readings in a For Each loop, or {{ $node["UNS Fetch Data"].records[0].value }} for the latest.

Fetch Maximum History for Trend Analysis

Field	Value
UNS Topic	`mHv1.0/acme-corp/plant-1/assembly/robot-arm/temperature`
Limit	`1000`

Downstream usage: Feed up to 1,000 recent records into a downstream calculation node for trend analysis or anomaly detection.

Dynamic Topic from Upstream Node

Field	Value
UNS Topic	`{{ $node["Set"].topic }}`
Limit	`10`

Downstream usage: The topic is dynamically determined by an upstream Set node, enabling reusable fetch logic across different data sources.

UNS Search Nodes

Overview

The UNS Search Nodes node discovers topics in the Unified Namespace by keyword. It returns matching topic metadata with pagination support, making it useful for dynamic topic discovery, namespace exploration, and building guided selection flows.

Node Handles

Handle	Position	Description
Input (`in`)	Left	Receives data from the upstream node.
Output (`out`)	Right	Sends the search results to downstream nodes.

Parameters

Field	UI Control	Data Type	Required	Default	Validation	Description
Search Keyword	Expression Field (single-line input with preview)	string	Yes	`""`	Minimum 3 characters (unless it's an expression). Must not resolve to empty.	Keyword to search for in UNS topic names. Supports expressions.
Offset	Number input	number	No	`0`	Must be ≥ 0	Number of results to skip for pagination.
Limit	Number input	number	No	`10`	1–1,000 (clamped to 1,000 if exceeded)	Maximum number of results to return.

Settings

Execution Settings

Setting	Options	Default	Description
Timeout (seconds)	1–600	Pipeline default	Maximum execution time for this node.
Retry on Timeout	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry if the node times out.
Retry on Fail	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry on failure. When Enabled, reveals Advanced Retry Configuration.
On Error	Pipeline Default / Stop Pipeline / Continue Execution	Pipeline Default	Behavior when the node fails after all retries.

Advanced Retry Configuration (visible when Retry on Fail = Enabled)

Field	Type	Default	Range	Description
Max Attempts	number	3	1–10	Maximum retry attempts.
Initial Delay (ms)	number	1000	100–30,000	Wait before first retry.
Max Delay (ms)	number	120000	1,000–300,000	Upper bound for backoff delay.
Multiplier	number	2.0	1.0–5.0	Exponential backoff multiplier.
Jitter Factor	number	0.1	0–0.5	Random jitter.

Output Data Structure

{
  "topics": [
    {
      "id": "topic-abc-123",
      "name": "temperature",
      "parentId": "node-xyz-789",
      "parentName": "robot-arm",
      "createdAt": "2026-01-15T10:00:00Z",
      "updatedAt": "2026-02-11T14:10:00Z"
    }
  ],
  "total": 42,
  "offset": 0,
  "limit": 10,
  "keyword": "temperature"
}

Field	Type	Description
`topics`	array	Array of matching topic metadata objects.
`topics[].id`	string	Unique topic node identifier.
`topics[].name`	string	Topic node name (the leaf segment of the topic path).
`topics[].parentId`	string	ID of the parent node in the namespace tree.
`topics[].parentName`	string	Name of the parent node.
`topics[].createdAt`	string	ISO 8601 timestamp of when the topic was created.
`topics[].updatedAt`	string	ISO 8601 timestamp of the last update.
`total`	number	Total number of matching results (across all pages).
`offset`	number	The offset used in this query.
`limit`	number	The limit used in this query.
`keyword`	string	The keyword that was searched.

Referencing in Downstream Nodes

{{ $node["UNS Search Nodes"].topics }}          → the full topics array
{{ $node["UNS Search Nodes"].topics[0].name }}  → name of the first match
{{ $node["UNS Search Nodes"].total }}           → total matches found
{{ $node["UNS Search Nodes"].keyword }}         → the search keyword used

Validation Rules

Rule	Error Message
Node name is required	"UNS Search Nodes node must have a name"
Search keyword is required	"Search keyword is required"
Keyword must be at least 3 characters (unless expression)	"Search keyword must be at least 3 characters"
Offset must be non-negative	"Offset must be a non-negative number"
Limit must be between 1 and 1,000	"Limit must be between 1 and 1000"
Keyword must resolve to non-empty string	"keyword resolved to empty string"

Usage Examples

Discover All Temperature Topics

Field	Value
Search Keyword	`temperature`
Offset	`0`
Limit	`50`

Downstream usage: {{ $node["UNS Search Nodes"].topics }} in a For Each loop to process each discovered temperature topic.

Paginated Search with Dynamic Keyword

Field	Value
Search Keyword	`{{ $trigger.payload.searchTerm }}`
Offset	`{{ $trigger.payload.page * 20 }}`
Limit	`20`

Downstream usage: Build a searchable topic browser where the keyword and page come from a webhook trigger or manual input.

Namespace Audit

Field	Value
Search Keyword	`alarm`
Offset	`0`
Limit	`1000`

Downstream usage: Discover all alarm-related topics in the namespace for an audit report. {{ $node["UNS Search Nodes"].total }} shows the full count.

Best Practices

Topic Naming Conventions

Follow the ISA-95 hierarchy: enterprise/site/area/line/cell/resource
Use lowercase, hyphen-separated segments: acme-corp/plant-1/assembly/robot-arm
Place measured values as leaf nodes: .../robot-arm/temperature, .../robot-arm/status
Keep topic paths stable — changing paths breaks downstream subscribers

Expression-Driven Topics

Use expressions like {{ $trigger._metadata.topic }} to build dynamic, reusable pipelines that work across multiple topics
Combine static prefixes with dynamic suffixes: mHv1.0/acme-corp/{{ $node["Set"].area }}/temperature
Always validate that expressions resolve to non-empty strings before publishing

Error Handling for UNS Nodes

Enable Retry on Fail for publish operations to handle transient UNS Manager unavailability
Use Continue Execution on error for fetch and search nodes in non-critical data paths
Use Stop Pipeline on error for publish nodes in critical data paths where data loss is unacceptable

Performance Considerations

Keep fetch Limit values as low as practical — fetching 1,000 records when you need 10 wastes resources
When using UNS Search in a loop, add pagination to avoid fetching all results at once

Overview​

Topic Structure​

Available Nodes​

UNS Topic Selector​

How It Works​

Expression Preview States​

UNS Publish​

Overview​

Node Handles​

Parameters​

Settings​

Output Data Structure​

Validation Rules​

Usage Examples​

Publish Transformed Sensor Data​

Publish Aggregated KPIs​

Dynamic Topic from Trigger Data​

UNS Fetch Data​

Overview​

Node Handles​

Parameters​

Settings​

Output Data Structure​

Validation Rules​

Usage Examples​

Fetch Latest 5 Readings​

Fetch Maximum History for Trend Analysis​

Dynamic Topic from Upstream Node​

UNS Search Nodes​

Overview​

Node Handles​

Parameters​

Settings​

Output Data Structure​

Validation Rules​

Usage Examples​

Discover All Temperature Topics​

Paginated Search with Dynamic Keyword​

Namespace Audit​

Best Practices​

Topic Naming Conventions​

Expression-Driven Topics​

Error Handling for UNS Nodes​

Performance Considerations​

Overview

Topic Structure

Available Nodes

UNS Topic Selector

How It Works

Expression Preview States

UNS Publish

Overview

Node Handles

Parameters

Settings

Output Data Structure

Validation Rules

Usage Examples

Publish Transformed Sensor Data

Publish Aggregated KPIs

Dynamic Topic from Trigger Data

UNS Fetch Data

Overview

Node Handles

Parameters

Settings

Output Data Structure

Validation Rules

Usage Examples

Fetch Latest 5 Readings

Fetch Maximum History for Trend Analysis

Dynamic Topic from Upstream Node

UNS Search Nodes

Overview

Node Handles

Parameters

Settings

Output Data Structure

Validation Rules

Usage Examples

Discover All Temperature Topics

Paginated Search with Dynamic Keyword

Namespace Audit

Best Practices

Topic Naming Conventions

Expression-Driven Topics

Error Handling for UNS Nodes

Performance Considerations