** A Practical Architecture for User Modeling in a Hypermedia-based
Information System

Julita Vassileva
Siemens AG Corporation, Germany

presented by
Nitin Nick Sawhney
October 10, 1994

** Why an AUI for Browsing? **

* Easy to get lost in a complex network of nodes
* Help user understand what links mean in their context
* User Modeling helps support users navigation
; Support Novice users - Ensure a smaller browsing space
; Support Expert users - Large browsing space and direct access
* Combine User Modeling with data protection & access privileges
* Provide adaption at discrete times - after informing the user 
* Support collaborative work?

** User Modeling for HYNECOS Hospital Information System **

* Multimedia Data  
; Patients, Personnel, Hospital stations, & Medical concepts
* Broad group of potential users
; Doctors, Nurses, Students, Hospital Personnel
* Browsing space (amount of information) too big
* Context of users tasks - basis for filtering information
* Several schemas of task hierarchy created reflecting different tasks 
  and Info needs - based on interviews

** Factors in User Modeling **

* The hypermedia system is fixed and can only be viewed
* Clearly identifiable categories of users
* Many factors influencing information needs of users 
; Task, place, profession, and rank - (priorities?)
* Information needed is known based on context of tasks
* Decomposable tasks - hierarchically organized with mutually dependent 
  information
* New tasks considered wrt. other tasks in hierarchy - less knowledge 
  engineering required

** Other User Modeling Issues **

* Direct Access (SQL Query) vs. Browsing - explicitly represent experience 
  to resolve conflict
* Adaptive - infer experience from users browsing
vs.
* Adaptable - allow user to change level of experience
* High Adaption causes loss of coherent mental model
* Quick access & absolute confidence in data important in medical domain
* Maximum Individualization vs. Group User Model
* Data protection from unauthorized access

** Architecture for User Modeling **

Three layer structure added to existing hypermedia system:
I. Task Hierarchies: Representations of user tasks or views
II. User Classes: Access Constraints and form of presentation
III. Individual User Model:  level of experience

Task Hierarchies: 
Every Task - specific information needs (entity)
* Specific Task - lower in hierarchy (limited view of hypermedia)
* High level task- move up in hierarchy (wider view)
* Free Browsing with an Anchor vs. Restricted Browsing

** Creation of User Classes **

* Overlapping user classes 
; Different Info. needs, access rights, forms of presentation
* Inheritance in task hierarchies of classes with same profession
* Higher ranking users have special rights:
; Access large amount of data not part of task hierarchy
; Modify data when not allowed in context of current task
* User class relate many Individual User Model          
; Missing parameters inherited from user class
; Individual UM can be changed by user and by system
; Experience level - access node to hypermedia entities

** Features of HYNECOS **

* Context of interaction based on task hierarchy and navigation space
* Adaption to users needs at discrete points in time after users permission.  
; Continuously looks at users level of experience
; Considers types of representation retrieved most often
; Revises task hierarchies based on non-optimal behavior
* Adaptability of user model:
; Supports modification of individual task hierarchy - 
  library of task aggregates
; Creation of new tasks and add to task library
; Style of viewing - Free vs Restricted
; Changing Level of Experience & Presentation Preferences

** Questions **

* Should the system support ad-hoc queries and how?
* What about novice or expert users that not part of an existing user class?
* How does the Group Model support Cooperative Work?
* Would such an architecture support other domains or Hypermedia aspects.

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