rfc-9652

The Link-Template HTTP Header Field

M. Nottingham

date2024-09 streamIETF areawit wghttpapi statusPROPOSED STANDARD pages5 canonicalhttps://www.rfc-editor.org/rfc/rfc9652 doi10.17487/RFC9652

This specification defines the Link-Template HTTP header field, providing a means for describing the structure of a link between two resources so that new links can be generated.

Extracted elements (12)

design-rationale §2.1

The 'var-base' Parameter exists to allow template variables to be globally identified via URIs, enabling dereferencing to discover the syntax or semantics of a variable. The specification intentionally leaves the format of such information out of scope.

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interoperability-note §2

Some target attribute names will not serialize as Structured Field Parameter keys (per Section 3.1.2 of RFC 9651), which implementations must account for when encoding link target attributes.

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interoperability-note §1

The Link-Template header field is complementary to, not a replacement for, the Link header field defined in RFC 8288. The Link header field carries links directly while Link-Template carries URI Templates for constructing links.

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normative-requirement §2 MUST

Implementations MUST support all levels of URI Template defined by RFC 6570 in the link String and the 'anchor' Parameter.

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normative-requirement §2 MUST

Target attribute Parameter values MUST be Strings, unless they contain non-ASCII characters, in which case they MUST be Display Strings.

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normative-requirement §2 MUST

The 'anchor' and 'rel' Parameters on the Link-Template header field MUST be Strings, consistent with their usage in the Link header field.

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normative-requirement §2 MAY

The 'anchor' Parameter MAY contain a URI Template, allowing the link context itself to be templated (e.g., anchor="#{book_id}").

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protocol-element §2

The Link-Template header field is a Structured Field whose value is a List of Strings, where each String contains a URI Template and can have Parameters carrying metadata. It is semantically equivalent to the Link header field except that the link target and link anchor can contain URI Templates.

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protocol-element §2.1

The 'var-base' Parameter on a templated link conveys a URI-reference used as a base URI for variable names in the URI Template, allowing template variables to be globally identified rather than context-specific.

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protocol-element §2.1

To determine the URI for a given variable under 'var-base', the value is used as a base URI in reference resolution (per RFC 3986). If the resulting URI is still relative, the link context is used as a further base URI per the Web Linking specification.

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registry §4

This specification registers 'Link-Template' as a Permanent field name in the IANA Hypertext Transfer Protocol (HTTP) Field Name Registry.

http, registry

security-consideration §3

The security considerations for the Link header field (RFC 8288) and for URI Templates (RFC 6570) both apply to Link-Template. Target attributes conveyed via Display Strings are vulnerable to a wide variety of attacks; implementers should consult Unicode Technical Report #36 for handling guidance.

http, security