Peter Brusilovsky

Index What is adaptive navigation support? History behind adaptive navigation support Adaptation technologies that provide adaptive navigation support Adaptation mechanisms for adaptive navigation support Adaptive navigation support beyond hypermedia

What is Adaptive Navigation Support? Specific group of technologies that help the user navigate through the hyperspace by adapting to his goals, preferences and knowledge The motivation is to Help the user achieve the goals faster Reduce navigation overhead Increase user’s satisfaction with the system Used in application areas ranging from e-commerce to e-learning and in virtual museums

History behind adaptive navigation support Research started in early 1990’s Problems related to inefficient navigation and the problem of being lost in the hypermedia Early navigation support technologies used manual indexing and provided navigation support within a closed corpus of documents The Web provided an attractive platform for adaptive hypermedia applications Research got divided into two parts: Using the known adaptive hypermedia technologies in the new web context Developing new technologies and new mechanisms Focus on exploring real world systems rather than lab level systems

Adaptation Technologies Direct guidance Link Ordering Link Hiding Link Annotation Link Generation

Direct Guidance Suggests the next best page for the user to visit according to the user’s goal, knowledge or preference Needs the user model to know the user’s goals, knowledge and preferences Direct guidance can be presented to the user in two ways If the link is already on the page, it can be outlined or emphasized. Examples WebWatcher and Personal WebWatcher System can create a dynamic “Next” link which is connected to the next best page

Direct Guidance Direct guidance provides no support for users who do not wish to follow the system’s suggestions Popular in adaptive educational hypermedia systems

Link Ordering (Adaptive Sorting) Prioritize all the links of a page according to some user valuable criteria from the user model The closer to the top, the more relevant the link is The links can be manually reordered by dragging Manual link reordering is considered by the system as a means of relevance feedback and is used to update the user model.

Link Ordering Cannot be used for contextual links or maps (index page or table of contents) This technology makes the order of links unstable (it may change each time the user enters the page) Appropriate where all or some of the pages have an unstable set of links like adaptive news systems

Link Hiding Restricts the navigation space by hiding, removing or disabling links to irrelevant pages Protects users from the complexity of the whole hyperspace and reduces cognitive overload Based on the separation of three features of a link, the following variants of link hiding are possible Link removal-removes the link as well as the anchor Link hiding- preserves the anchor but removes all visual indications that it is a link Link disabling-removes the functionality

Link Hiding Used is educational hypermedia systems Link hiding is a unidirectional technology Hiding can distinguish between only two states for related pages – relevant or non relevant

Link Annotation Augment links with some visual cues to let the user know more about the page behind the annotated link Icon based annotations and mouseovers are the most popular techniques Preserves a stable order with the links Annotation can distinguish up to six states for related pages

Link Generation Newest adaptive navigation support technology Creates new, non-authored links on a page Three kinds of link generation Discovering new links and adding them permanently to the set of existing links Generating links for similarity based navigation between items Dynamic recommendation of links that are useful within the current context to the current user

Link Generation vs. Web Recommender Recommender systems suggest a list of items that are relevant to the user’s short or long terms needs Navigation systems focus on helping users to find their way through hyperspace by adapting links on a page

Comparison of the technologies Direct Guidance SortingHidingAnnotationGeneration Contextual links OKDisablingOK Non- contextual links OK Table of Contents OK IndexOK Hyperspace maps OK

Adaptation Mechanisms for Adaptive Navigation Support Simple Adaptation Mechanisms Content-Based Mechanisms Social Mechanisms Indexing-Based Mechanisms

Simple Adaptation Mechanisms Do not require advanced adaptation algorithms History-Based Mechanisms Count how many times each node in the hyperspace has been visited and attempt to represent this information visually Trigger-Based Mechanisms State of a link is connected with an event Once the event happens, the link appearance changes Used by learning management systems Progress-Based Mechanisms Tracks the user visit to a page on a deeper level like time spent reading a page or amount of page exploration

Content-Based Mechanisms Make a decision whether to suggest the user a path to a specific page by analyzing page content If the links is followed, the user profile is updated accordingly

Syskill & Webert

ScentTrails

Social Mechanisms Based on the idea of social navigation Offered in two forms Direct-direct interaction of users with each other in information space For direct social navigation, annotate links to pages that are currently visited by other users with special icons Indirect-traces the activities of the community of users History enriched environments – footprint based approach Collaborative filtering systems

CourseAgent system

Indexing-Based Mechanisms Use manually-produced concept-level document representation and concept-overlay models Content of each page is expressed in terms of external concept level models The same external model is used for building an overlay user model and page indexing The external model used is generally a concept level domain model

Classification of Indexing Approaches Cardinality Single-concept indexing- each page is related to only one external model concept Multi-concept indexing-each page can be related to many concepts Navigation-is the link between concept and a page on a conceptual level or does it define a navigational path? Expressive Power-amount of information associated with every link between a concept and a page Role Weight

Basic Approaches to Indexing Concept Based Hyperspace-used in systems that use single concept indexing Simple concept based hyperspace Used in systems that have exactly one page in every system Hyperspace is the exact replica of the external model Each concept of external model is represented exactly by one node of the hyperspace Enhanced concept based hyperspace Each concept has a corresponding hub page in the hyperspace Used in adaptive e-learning systems Page Indexing Used in systems that use multi concept indexing Each hypermedia page is indexed with several external model concepts Concept based Navigation Combination of the above two approaches

Adaptive Navigation Support for Virtual Environments Text based virtual environments MUDs MOOs Web Virtual Reality