A frontmatter (note: Frontmatter) id does not follow the identifier (note: Identifier) pattern, lowercase (3 passages, no note) letters (17 passages, no note), digits (4 passages, no note) and hyphens (4 passages, no note) in a first segment (11 passages, no note), then at least one more segment after a slash. The declared value (35 passages, no note) is ignored and the identifier derives from the source (note: Source) name and the file path, as if no id had been written, so that the page still exists at a predictable address (56 passages, no note); the finding (note: Finding) says which value was refused (3 passages, no note).
Check (note: Check) E-ID-INVALID, severity (note: Severity) error (29 passages, no note) by default, documented with a before and after example in the check pages. The severity can be overridden per project (note: Project) or per repository (note: Knowledge repository).