Achieving Coordination Through Dynamic Construction of Open - - PowerPoint PPT Presentation

Achieving Coordination Through Dynamic Construction of Open Workflows

Louis Thomas, Justin Wilson, Gruia-Catalin Roman, and Christopher Gill Mobilab Department of Computer Science and Engineering

Workflows

• Workflows are an established technology



Coordination mechanism for integration of services

• A workflow is a graph of tasks that are executed to

accomplish a goal

• Example: Printing a photo album on line



Upload – Print – Bind – Deliver

• Goal: Use workflows for coordination in mobile ad hoc

communities

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

A more flexible approach is required

New Idea: Open Workflow

• Specify, construct, and execute a custom, context-specific

workflow in response to expressed needs

• Respond to unpredictable and evolving circumstances



Evolving community of participants



Decouple task knowledge from service capability



Space and time constraints



Ad hoc wireless connectivity

• Goes beyond traditional workflow approaches

3

Open Workflow Life Cycle

4

Construction Allocation Execution

Open Workflow Example

5

Idea For Course

⋁

Create Course Course Name Syllabus Book List

Professor

Book List

⋁

Order Book Book On Reserve

Department Librarian

• Knowhow within a Community of Participants

Department Chair

Course Name

⋀

Register Course Course Approved Course Registered Syllabus

⋁

Approve Course Course Approved

Open Workflow Example

6

• A workflow is constructed in response to expressed need,

stated as a specification

Professor

Idea For Course

ι

Course Registered

ω

Idea For Course

⋁

Create Course Course Name Syllabus Book List Book List

⋁

Order Book Book On Reserve Syllabus

⋁

Approve Course Course Approved Course Name

⋀

Register Course Course Approved Course Registered

Open Workflow Construction Algorithm

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• Create a supergraph

Idea For Course Course Registered

ι ω

Professor

• Dept. Librarian

Department Chair

Idea For Course

⋁

Create Course Course Name Syllabus Book List Book List

⋁

Order Book Book On Reserve Syllabus

⋁

Approve Course Course Approved Course Name

⋀

Register Course Course Approved Course Registered

Open Workflow Construction Algorithm

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• Identify reachable nodes

Idea For Course Create Course Course Name Syllabus Book List Approve Course Register Course Course Approved Course Registered Order Book Book On Reserve

⋁ 1 2 2 ⋁ 3 ι ω 4 ⋀ 5 6 2 ⋁ 3 4

Book List Order Book Book On Reserve

⋁ 1 2 2 ⋁ 3 4 ⋀ 5 6 2 ⋁ 3 4

Open Workflow Construction Algorithm

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• Identify valid workflow

Idea For Course Create Course Course Name Syllabus Approve Course Register Course Course Approved Course Registered

ι ω

Idea For Course

⋁

Create Course Course Name Syllabus

⋁

Approve Course

⋀

Register Course Course Approved Course Registered

ι ω

Open Workflow Allocation and Execution

• Allocation

 Participants bid to execute tasks, making firm commitments

• Must be have corresponding service
• Must have time in schedule to travel as necessary
• Execution

 Wait for location, time, required inputs  Execute service  Communicate service outputs

• Move freely (so long as commitments are met!)

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Open Workflow Middleware Architecture

11 Location Schedule Service Execution Fragment Auction Participation Service Instances UI UI UI UI UI Workflow Initiator Workflow UI UI Workflow Workspaces Auction

Inter-service Messages

Execution Subsystem Construction Subsystem

Communications Layer

Auction Messages Workflow Fragment Messages Service Feasibility Messages

Open Workflow Application in Action

12

Open Workflow System Performance

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Time taken to construct different sized workflows in a community of four wireless devices

Work in Progress

• Expressiveness
• Dynamics
• Knowledge Management

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Conclusions

• Mobile devices demand new approaches for collaboration
• We proposed the Open Workflow paradigm
• We presented a construction algorithm and an application

built on the open workflow paradigm

• Our source code is available online

http://mobilab.cse.wustl.edu/projects/openworkflow/

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