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Use this page to look up expression syntax in Sift. Expressions are written using Common Expression Language (CEL) and are used in Calculated Channels, Rules, and User-Defined Functions.

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Channel references

Each input Channel selected when configuring a Rule, Calculated Channel, or User-Defined Function is automatically assigned a shorthand variable based on selection order: $1, $2, $3, and so on. Use these variables to reference the corresponding Channel in your expression.

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Operators

The following table lists the CEL operators supported in Sift. Not all CEL operators are supported.

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Functions

The Expression Syntax panel in the expression editor organizes functions into the following sections:

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Stateful functions

Stateful functions compute values using data from preceding rows within a rolling time window of up to 10 minutes. Use them to track trends, detect gradual changes, and compute time-based metrics across telemetry data. The following table lists all available stateful functions with expanded descriptions to help you choose the right function for your use case.

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User-Defined Functions

The User-Defined Functions section of the expression editor lists all named, reusable functions created across your organization. Call any function by name directly in your expression.

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Behavior

The following table describes known constraints and behaviors to be aware of when writing expressions in Sift.