An Approach to Task Modelling for User Interface Design Costin Pribeanu National Institute for Research and Development in Informatics, Bucureşti, Romania

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

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

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

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 InterleavingT1 ||| T2 SynchronizationT1 |[]| T2 EnablingT1 >> T2 Enabling with info passT1 [ ]>> T2 DisablingT1 [> T2 Suspend / resumeT1 |> T2 Optional (unary)[T1] Iteration (unary)T1*

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

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)

Data model elements Role Object Relationship 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));

Data model representation

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

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

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)

Functional layer Planning (functional) goals Specified during early task analysis Starting with high level business goals (application functions) Unit tasks “what to do” Unit task Functional goal

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 Operational layer Basic tasks

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

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