---
id: LANG-20
family: GR-LANG
level: core
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/gr-lang/lang-20
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# LANG-20 — Testing whether a path exists

*GR-LANG (Part I) · level: core · profiles: runtime · added in 1.0*

The test answers for every path, including the two that have no obvious answer: one that cannot be walked, and one with nothing in it.

## The rule

> **Normative.** This is the rule.
>
> 1. Testing a path for existence reports whether that path can be read, and answers for every path.
>
> 2. A path that cannot be read reports absence, a property path applied to a scalar among them, since a scalar has no property to read (LANG-8).
>
> 3. The empty path consumes no segments and therefore denotes the evaluation context itself, which is always present, so the empty path reports presence.

## Related rules

- Names: LANG-8

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.