[1] [CITE@en-US[[[Data Resource]] | Frictionless Standards]], [TIME[2023-09-28T10:34:45.000Z]], [TIME[2023-11-25T09:20:43.722Z]] <https://specs.frictionlessdata.io/data-resource/#url-or-path>

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- [MUST[MUST]] either be a URL or a POSIX path
-URLs MUST be fully qualified. MUST be using either http or https scheme. (Absence of a scheme indicates [MUST[MUST]] be a POSIX path)
-POSIX paths (unix-style with [CODE[/]] as separator) are supported for referencing local files, with the security restraint that they [MUST[MUST]] be relative siblings or children of the descriptor. Absolute paths (/) and relative parent paths (…/) MUST NOT be used, and implementations SHOULD NOT support these path types.

[2] >>1 のサイトの他のいくつもの仕様書から参照されています。