1. WOSS 04 1 Task-based Self-adaptation David Garlan Bradley Schmerl Joao Sousa Vahe Poladian Carnegie Mellon University WOSS’04

2. WOSS 04 2 Key Argument of Paper There may be many ways to adapt a system. How do you choose which adaptation is best? Example: watching a video, bandwidth drops Adaptation could: 1.reduce frame rate 2.reduce size 3.increase granularity 4.eliminate color Proper decision requires knowledge of user intent

3. WOSS 04 3 Outline Context of problem and problem definition –What does self-management mean to us? –What aspects are we addressing? What is a task? –What applications are we targeting? How do you get tasks into the system? –What are the key ideas/approaches? How can tasks help in adaptation? Research challenges –What are we NOT addressing?

4. WOSS 04 4 Context “Everyday computing” –Use of computing by ordinary users to handle day-to-day activities Increasingly complex array of technologies –Heterogeneous mix of platforms, services –Ubiquitous access to computing and communication Variable resources and mobility –Different qualities of service at different times

5. WOSS 04 5 The Problem Managing technology becomes a full-time headache Can the system automatically adjust itself to maximize utility for a user? –Adjusting for resource variability –Choosing most appropriate configurations –Reconfiguring when necessary

6. WOSS 04 6 Answer No (today) The problem is we don’t know what the user wants or needs –Utilities are based on average/default cases for individual applications Solution: Explicitly represent user tasks

7. WOSS 04 7 Project Aura We have been investigating task-based adaptation in the context of Project Aura –Pervasive computing environments –Resource variability, user mobility –Heterogeneity –Goal: minimize user distraction

8. WOSS 04 8 Tasks Tasks: –Intuitively: encode user goals. E.g., planning a trip, preparing a lecture –A locus for desired quality attributes. E.g., important to maintain resolution of video Once made explicit, tasks can help in adaptation by: –Providing a yardstick against which to measure the behavior of a system –Helping to choose most appropriate adaptations

9. WOSS 04 9 What is a Task? Many possible answers –An application/service –A collection of coordinated services –A workflow –A set of goals and constraints None (task=application) Increasing Cost/Capability Interacting Services Personal Workflow Knowledge- based Service Sets (snapshot) Agents Our Focus

10. WOSS 04 10 Users Physical Devices OS/Network ApplicationsToday Users Physical Devices OS/Network Services TasksTomorrow

11. WOSS 04 11 How to get Tasks into a System Environment Support user tasks available services & resources probes to reflect current QoS Environment Management How to configure environment monitor capabilities & resources map services & state to suppliers continually optimize to maximize utility Task Management What the user needs monitor task, context, preferences map tasks to services manage complex tasks

12. WOSS 04 12 Separation of Adaptation Concerns Task layer specifies what are the appropriate adaptations –Quality of service, knowledge of preferences, knowledge of task steps –An run-time embodiment of requirements Environment layer does adaptation –Map task requirements to available services –Make trade-offs to maximize user utility given available services and resources

13. WOSS 04 13 Mapping between Tasks and Configurations Utility-theoretic approach –Maximize utility based on available services and resources –Allow user preferences for service providers Efficient algorithms to calculate utility –See ICSE’04 paper Reconfigure selectively –To improve utility for user –Task-specific reconfiguration penalty

14. WOSS 04 14 What exists Current implementation –Specify tasks and task-specific utilities –Pause and resume tasks Across time and space –Reconfigure tasks automatically Based on utility calculations –Wrapped legacy applications User studies –Can users recognize variations in utility? –Can they specify utilities that they want?

15. WOSS 04 15 Research Challenges Improved utility evaluation algorithms –Taking into account the future Adding stronger notion of context –Tasks may only make sense in certain logical contexts Multi-level adaptations –Adaptation can happen at several levels Adapting to multi-user tasks –Competing requirements Beyond the “desktop” –For example, smart home tasks