Query Syntax

Metrics and some actions use a SQL-like query to read data from the platform's runtime database. This page describes the query format and the conventions used throughout XAL files.

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Basic structure

A query follows standard SQL SELECT syntax:

SELECT <column> FROM <table> WHERE groupLabel = 'this.GROUPLABEL'

The most common form reads the global state status of another automaton:

SELECT GLOBALSTATE_STATUS FROM Scenario_Follower_Manager WHERE groupLabel = 'this.GROUPLABEL'

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Table naming convention

The table name encodes the file and automaton being queried, using an underscore separator:

<FilePrefix>_<AutomatonId>

Where <FilePrefix> is derived from the XAL file name (without extension, with hyphens replaced by underscores) and <AutomatonId> is the Id attribute of the target automaton.

Examples:

File	Automaton	Table name
scenario.xal	Follower_Manager	Scenario_Follower_Manager
patcher.xal	Dispatcher	PATCHER_DISPATCHER
drone-leader.xal	C2_Link_Monitor	Scenario_C2_Link_Monitor

Note

The exact casing convention may vary depending on the deployment. Follow the conventions used in existing files within the same project.

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The groupLabel binding

The WHERE groupLabel = 'this.GROUPLABEL' clause is mandatory in all automaton state queries. It binds the query to the specific instance of the target automaton that is running on the same monitored object as the querying automaton.

Without this binding, the query would return results from all running instances of the target automaton, regardless of which object they belong to.

this.GROUPLABEL is a runtime placeholder — the platform substitutes it with the actual group label of the current instance at execution time.

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Querying specific columns

In addition to GLOBALSTATE_STATUS, queries can retrieve other global state variables:

SELECT GLOBALSTATE_STATUS as "status", GLOBALSTATE_RelocatedDBs as "RelocatedDBs"
FROM PATCHER_RelocateDb
WHERE groupLabel = 'this.DbHostName'

The as alias maps the column to the output parameter that receives the value in the automaton's global state.

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Alternative WHERE clauses

Some queries use a specific global state variable in the WHERE clause instead of this.GROUPLABEL:

WHERE groupLabel = 'this.DbHostName'

This targets the instance associated with the value stored in the DbHostName variable of the current automaton's global state.

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Queries in the XAL Designer

In the XAL Designer, the query is entered in the Query field of the Metric configuration section. The designer does not validate the query syntax — correctness is verified by the platform at runtime.

When a state has a query configured on its metric, a grid icon appears in the top-right corner of the state node on the canvas.