An Approach to Task Modelling for User Interface Design

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An Approach to Task Modelling for User Interface
Design

• Costin Pribeanu
• National Institute for Research and Development
  in Informatics, Bucuresti, Romania
• E-mail pribeanu_at_ici.ro

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Content

• Introduction
• Related work
• Model-based design
• Using CTT for task representation
• The application domain model
• Mapping application functions onto user tasks
• Using the task model to filter data model
  elements
• Task modeling
• Layers in task decomposition
• Decomposition at operational level
• Conclusion

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Introduction

• Model-based design of user interfaces
• addressing methodological aspects models,
  methods and tools
• capturing design knowledge
• contributing models user, task, domain,
• interface models presentation and dialog
• task-based design task model is the key model
• Motivation and objectives
• answering the mapping problem relationships
  between models
• presenting a layered approach to task modeling
• exploiting the information contained in the
  domain model
• deriving the presentation from the task model

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The mapping problem

• Key problem in model-based approaches
• model transformation from abstract to concrete
  level
• relationships between different models
• Related work
• Clerck et al. (2004) preserving consistency
  between models
• Florins Vanderdonckt (2004) graceful usability
  degradation
• Limburg Vanderdonckt (2004) description
  language tools
• Aspects to consider
• the model type (e.g. domain, task, platform )
• the hierarchical structure of each model
• the progression level along the development cycle

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Tools for task representation

• Concur Task Tree (CTT) notation
• Graphical task representation
• Abstract Application Interaction User Cooperative
• Temporal operators between sibling tasks
• Choice T1 T2
• Order independency T1 T2
• Interleaving T1 T2
• Synchronization T1 T2
• Enabling T1 gtgt T2
• Enabling with info pass T1 gtgt T2
• Disabling T1 gt T2
• Suspend / resume T1 gt T2
• Optional (unary) T1
• Iteration (unary) T1

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Application functions

• Application domain model
• concepts related to the domain of target
  applications
• application functions and data model
• Application functions
• high level functions corresponding to bussiness
  goals
• carried on by user tasks
• Example data management in a trade company

Functional goal
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Data model

• Data model elements
• Domain objects (entities)
• Attributes
• Relationships between objects (and roles)
• Model representation
• ERA formalism (Entity-Relationship-Attribute)
• DB-MAIN tool
• graphical representation of data model elements
• expressive for roles and cardinalities
• output capabilities (SQL and XML)

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Data model elements
Object
Relationship
Role
Object attribute
Cardinality
Relationship attribute
create table ORDER ( ID_ORD char(10) not
null, Order_Id -- Index attribute not
implemented -- not null, Order_No numeric(6)
not null, Order_Date date not null,
Delivery_Date date not null, Pay_Mode
char(1) not null, Order_Value numeric(9,2)
not null, constraint ID primary key
(ID_ORD))
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Data model representation
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Centrality of elements

• Central domain objects
• Targetted by the user task
• Central relationships
• Relationships of central objects
• Helps the user to understand the information
  displayed
• Relevant roles - cardinality
• Reveals repetitive tasks
• Helps in task decomposition
• The task model is filtering for relevance (UI
  design) data model elements
• Orders 1-N products

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Task modeling

• Task model
• goal hierarchy, tasks, temporal constraints
• Activity theory
• Activity motivation
• Actions (tasks in HCI) goal
• Operations (actions in HCI) operational
  conditions
• Operational conditions
• Variations in using the same interaction object
• actions
• Variations in the platform
• operational goals related to a given context of
  use

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Task decomposition

• Layers in task modeling
• Functional planning
• Operational
• Criteria for task decomposition
• Functional same business goal (functional)
• Semantic targetting same domain object or
  operation onto it (both)
• Object used using same external or interaction
  object (operational)
• User and work same user and role, similar work
  (cooperative)
• Temporal specific temporal constraint (both)

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Functional layer

• Planning (functional) goals
• Specified during early task analysis
• Starting with high level business goals
  (application functions)
• Unit tasks
• what to do

Functional goal
Unit task
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Operational layer

• Operational goals
• Specified during user interface design
• Starting with unit tasks
• Basic tasks
• depend on a given platform
• how to do it
• Basic task types
• Information control
• Function control

Unit task
Basic tasks
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Unit task decomposition

• Hierarchy of unit tasks
• Invoke the execution of another unit task
• Operational task structures
• Suggest AIO grouping in a task-based approach

Unit task
Unit task
Basic tasks
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Conclusion

• Task-based approach
• Starting with the task model
• Decomposition levels
• Functional task level
• resulting from mapping application functions onto
  user tasks
• Unit task level
• leaves in the functional-planning layer
• mapped onto AIO configuration
• Basic task level
• leaves in the operational level
• carried on with AIO