The declarative aspects of a resource (identification and naming) and its functional aspects (addressing and technical handling) weren't clearly distinct in the early specifications of the web, and the very definition of the concept has been the subject of long and still open debate involving difficult, and often arcane, technical, social, linguistic and philosophical issues.
The web is designed as a network of more or less static addressable objects, basically files and documents, linked using Uniform Resource Locators (URLs).
Familiar examples include an electronic document, an image, a service (e.g., "today's weather report for Los Angeles"), and a collection of other resources.
In January 2005, RFC 3986 makes this extension of the definition completely explicit: '…abstract concepts can be resources, such as the operators and operands of a mathematical equation, the types of a relationship (e.g., "parent" or "employee"), or numeric values (e.g., zero, one, and infinity).'
But it has been answered that such a distinction is impossible to enforce in practice, and famous standard vocabularies provide counter-examples widely used.
The general question of which kind of resources HTTP URI should or should not identify has been formerly known in W3C as the httpRange-14 issue, following its name on the list defined by the (TAG).
While this compromise seems to have met a consensus in the Semantic Web community, some of its prominent members such as Pat Hayes have expressed concerns both on its technical feasibility and conceptual foundation.
If the content of a web resource in the classical sense (a web page or on-line file) is clearly owned by its publisher, who can claim intellectual property on it, an abstract resource can be defined by an accumulation of RDF descriptions, not necessarily controlled by a unique publisher, and not necessarily consistent with each other.