Some constrained environments make this question easy to answer, for example, within HTML anchors or Gopher menu items. Less constrained environments, such as within running text, make it more difficult to answer without well-defined assumptions. A resource location standard needs to make any such assumptions explicit. 2.2.2 Resource Locator Producers Resource locators are produced in many ways, often by an agent that also interprets them. The provider of a resource may produce a locator for it, leaving the locator in places where it is intended to be discovered, such as an HTML page, a Gopher menu, or an announcement to an e-mail list.
Users are major producers of resource locators.
A user constructing one to share with others is responsible for conformance with locator standards. Sometimes a user composes a resource locator based on an educated guess and submits it to client software with the intent of establishing access. Such a user is a producer in a sense, but if the locator is purely for personal consumption the user is not bound by the requirements. This document considers the following aspects of uniqueness, but deliberately rejects them as requirements. It is incumbent upon a resource location standard that takes on this topic to be clear about which aspects it addresses.