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• Non-linear navigation - Hypertext is a non-sequential (non-linear) means of accessing texts. • Virtual structures - Hypertext presents different navigation options to the user ('virtual structures'), which may include some or all of the following: • Associative or lateral structures - Links between text items determined by semantic relationships only. This is the essential type of hypertext link. (eg a link to the meaning of 'convention' in the Racial Discrimination Act 1975) • Hierarchical structures - Tables of contents, menus and the like. • Sequential structures - Where information does have a natural sequential order, it can be represented (eg the [Previous] and [Next] buttons to go back and forward between the sections of a statute). • Overviews - Site maps and other structures to allow users to understand the structure of a whole site. • 'Fisheye views' - Overviews where the current location is represented in most detail, with the detail receding as the context gets further away. • Guided tours - Pre-defined useful paths through a site, for purposes such as teaching its use, or to demonstrate an argument. • User control - Because of the previous features, hypertext allows the user to determine which nodes are accessed, and in which order, at the time of reading. In this way (without getting too post-modern about it) hypertext reduces the authority and control of the author/system designed, and increases that of the reader. But this should not be exaggerated - the user can still only browse within the structures enabled by the system designed (unless user-defined links are supported). • Bearings - Hypertext structures provide various means to stop users getting lost ('bearings'). These may include: • Landmarks - Pre-defined nodes which can be accessed at any time. These may be defined by the system (for example, the Netscape icon) or by the user (bookmarks), or may be particular to certain sets of web pages (eg the [Title] button at the top of this page). • The user's backtrack path or history list - the ability to go back to where you came from (by one step or many), and to see that path represented visually (In Netscape, this is the 'Go' button on the menu bar). • Current node identification - the ability to see the identity of the current node you are browsing (for example, the title at the top of a Netscape screen), and even better an indication of its context (such as where it sits in the hierarchy of nodes being browsed). (eg see the top line in yellow on any of Nielsen's web pages) • User configurations - Hypertexts vary in the facilities they provide to increase user control, including: • Bookmarks are user-created landmarks; creation and saving of bookmarks is now standard. • User-added links between text items and nodes are one of the most powerful forms of user control (and essential to the ideas of Bush and Nelson discussed below). They are not yet standard on the web, but are available in many disk-based hypertext systems. • User annotations to nodes / text (and links to and from them) are not yet standard either. • Saved history lists in order to preserve a valuable path of research are often available.
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