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All glossary terms

Proxy & networking

Common Expression Language (CEL)

Common Expression Language (CEL) is a non-Turing-complete expression language for evaluating predicates and values in host applications. The language defines syntax and semantics, while each application decides which variables, functions, and operations are available.

Also known as CEL.

Why it matters in practice

A CEL expression has meaning only within the data and functions supplied by its host. A policy engine may use expressions to test request attributes, but the language does not itself define a firewall policy or guarantee a safe default. Reviewers should test expressions against representative inputs and host-specific behavior.

Example

A proxy rule evaluates a CEL expression over the request method and destination attributes exposed by that proxy.

Educational note

This definition is general information, not legal advice. It may omit facts that matter to a specific situation and does not establish or guarantee compliance.