Peter Brusilovsky

IndexWhat is adaptive navigation support?History behind adaptive navigation supportAdaptation technologies that provide

adaptive navigation supportAdaptation mechanisms for adaptive

navigation supportAdaptive 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 toHelp the user achieve the goals fasterReduce navigation overheadIncrease 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 supportResearch started in early 1990’s Problems related to inefficient navigation and the

problem of being lost in the hypermediaEarly 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 contextDeveloping new technologies and new mechanisms

Focus on exploring real world systems rather than lab level systems

Adaptation TechnologiesDirect guidanceLink OrderingLink HidingLink AnnotationLink Generation

Direct GuidanceSuggests 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 waysIf 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 GuidanceDirect 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 OrderingCannot 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 HidingRestricts the navigation space by hiding, removing

or disabling links to irrelevant pagesProtects users from the complexity of the whole

hyperspace and reduces cognitive overloadBased on the separation of three features of a link,

the following variants of link hiding are possibleLink removal-removes the link as well as the anchorLink hiding- preserves the anchor but removes all

visual indications that it is a linkLink disabling-removes the functionality

Link HidingUsed is educational hypermedia systemsLink hiding is a unidirectional technologyHiding can distinguish between only two

states for related pages – relevant or non relevant

Link AnnotationAugment 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 linksAnnotation can distinguish up to six states for

related pages

Link GenerationNewest adaptive navigation support technologyCreates new, non-authored links on a pageThree 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 RecommenderRecommender 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 technologiesDirect Guidance

Sorting Hiding Annotation

Generation

Contextual links

OK Disabling

OK

Non-contextual links

OK OK OK OK OK

Table of Contents

OK OK

Index OK OKHyperspace maps

OK OK OK

Adaptation Mechanisms for Adaptive Navigation SupportSimple Adaptation MechanismsContent-Based MechanismsSocial MechanismsIndexing-Based Mechanisms

Simple Adaptation MechanismsDo not require advanced adaptation algorithmsHistory-Based Mechanisms

Count how many times each node in the hyperspace has been visited and attempt to represent this information visually

Trigger-Based MechanismsState of a link is connected with an event Once the event happens, the link appearance changesUsed by learning management systems

Progress-Based MechanismsTracks the user visit to a page on a deeper level like

time spent reading a page or amount of page exploration

Content-Based MechanismsMake 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 MechanismsBased on the idea of social navigationOffered 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 iconsIndirect-traces the activities of the community of

users History enriched environments – footprint based

approach Collaborative filtering systems

CourseAgent system

Indexing-Based MechanismsUse 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 ApproachesCardinality

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 pageRoleWeight

Basic Approaches to IndexingConcept 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 conceptsConcept based Navigation

Combination of the above two approaches

Adaptive Navigation Support for Virtual Environments

Text based virtual environmentsMUDsMOOs

Web Virtual Reality