If you are an HTML guru, you will also know that there is a special element that can appear inside head elements, called link . All these are kinds of links too. Almost anything that includes some kind of electronic address, identifier, location or query is a link.
Topic maps allow external annotation of all sorts of data.
XLinks A link is an explicit relationship between two or more resources or portions of resources. The simple link is similar to HTML's a element type. The extended link contains arc and locator elements, and allows extended links of various kinds. Let us look at simple links and then extended links. A simple link can be expressed in two ways, which acheive the same function.