Uniform Resource Identifier

RFC 3986 uses URI as a general term and distinguishes uses such as locating a resource through a URL. An identifier can also act as a name; its existence does not establish that a downloadable file is currently available.

A scheme such as https or urn precedes the colon. Generic syntax supplies a shared framework while individual schemes further define permitted forms and interpretation.

References: [1]

A hierarchical form can contain authority, path, query and fragment components, but not every scheme needs all of them. Delimiters carry syntax, so percent-encoded data cannot be indiscriminately treated as literal separators.

Relative references need a base URI. They can preserve relationships within a relocated document collection but do not independently identify the target without that context.

URI normalization cannot apply one transformation to the whole string. RFC 3986 treats scheme and host case-insensitively, without making every other component lowercase. Percent-encoding hex case can be normalized and encoded unreserved characters decoded, but reserved characters can carry delimiter meaning. Decoding %2F to a slash can change path segmentation rather than merely simplify the spelling.

References: [1] [4]

IRIs introduce a broader Unicode character repertoire and mappings to URIs. Displayed characters, transport encodings and comparison rules must be distinguished; visual similarity alone does not establish identity.

Naming also has ownership boundaries. RFC 8820 explains why standards should respect scheme and resource owners rather than invent arbitrary fixed paths or infer universal semantics from incidental prefixes.

References: [2] [3]