Design Space

Adaptive web sites vary along a number of design axes.

• Types of adaptations. New pages may be created. Links may be added or removed, highlighted or rearranged. Text, link labels, or formatting may be altered.

• Customization vs. Transformation. Customization is modifying a web site to suit the needs of an individual user; customization necessitates creating a large number of versions of the web site -- one for each user. In contrast, transformation involves altering the site to make navigation easier for a large set of users. For example, a university web site may be reorganized to support one ``view'' for faculty members and a distinct view for students. In addition, certain transformations may seek to improve the site for all visitors.

• Content-based vs. Access-based. A site that uses content-based adaptation organizes and presents pages based on their content -- what the pages say and what they are about. Access-based adaptation uses the way past visitors have interacted with the site to guide how information is structured. Naturally, content-based and access-based adaptations are complementary and may be used together.

• Degree of automation. Excite and Yahoo's manually personalized home pages are a simple example of customization; we are interested in more automatic adaptation techniques. However, for feasibility, adaptive web sites are likely to be only partially automated.

We now survey previous work on adaptive web site using the vocabulary and distinctions introduced above.