6.1 Static Versus Dynamic Linking

In correspondence with other literature [Fou90] [Hal91], we define static and dynamic links as follows:

static link:

Static links are the common link type in most commercially available hypertext systems. Static links are defined by a hypertext author and are available afterwards to the reader (<A HREF....>-links in HTML). For static links the connections and link-endpoints are hardwired into the document by the author. There is no easy way to accommodate different user groups and to adjust the links in a modified hyperdocument.

dynamic link:

Dynamic links have been implemented only in a few experimental hypertext systems [Irl90][Fou90][Ega91]. Dynamically linked documents do not have any fixed link-endpoints (also called anchors). Instead the links are computed at runtime according to the needs of the user.

Halasz [Hal91] calls this discussion the "literalists vs. the virtualists". For literalists[6], structures and links are created and represented explicitly. Navigation is by following explicit structural connections. Examples of literalist systems are most of the existing hypermedia systems as, e.g., Intermedia [Utt89], NoteCards [Hal86], and KMS [Aks88]. Examples of virtualist systems include MICROCOSM [Fou90], SuperBook [Rem87], and CYBERMAP (described later in this book).

Dynamic links offer two distinct advantages compared to static links:

• Dynamic links propose a more flexible way of navigating in the hyperdocument because they are generated on the fly according to the varying needs of the readers.
• Dynamically linked documents are easy to modify because newly added or deleted nodes are (un)linked automatically to and from the existing nodes. Anyone who has ever tried to add or remove nodes from a complex hypertext document written by somebody else knows how difficult it is to avoid dangling links within the existing body of the hyperdocument.

Similarity links, where links are computed automatically based on similarity between nodes, are a special case of dynamic links. Similarity is discussed later in chapter 10.

As has been mentioned above and has been proven by actual examples [Fur89], it is very difficult to provide a fixed a priori linking structure for huge hyperdocuments. This is true in particular if the links should be able to satisfy the needs of various user groups with different capabilities and requirements. Dynamic linking addresses this problem by trying to figure out the needs of the reader dynamically and to only present the links that are appropriate in a particular situation.