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Addressing and influence

Addressing into a resource

XPath answers “where within a document,” which composes naturally with addressing that answers “which document.” XPointer does exactly this — it uses an XPath expression in a URI fragment to point into a specific part of an XML resource. So a full address layers two languages: a URI to the resource, an XPath into its structure. That two-layer shape — locate the resource, then descend into it — is the form much navigation takes.

From path syntax to query language

XPath grew well beyond selection. With 2.0/3.x and the data model it shares with XQuery, it gained sequences, a type system, and a large function library — a genuine query language for trees, not just a path notation.

Influence

The path-expression idea spread widely. CSS selectors address into the HTML/DOM tree in a related spirit; JSONPath and JMESPath carry the path-and-predicate model to JSON; XQuery builds directly on XPath. Whenever a system needs a compact way to address into structured data, it tends to reinvent something XPath-shaped.

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