1. Fast Conflict Detection for
Remote Collaborative Software Modeling
Jae young Bang March 8th, 2011

2. Outline Phase 1: year 2010 Phase 2: year 2011 Motivation
CoDesign Project Goals
Results
Phase 2: year 2011
Research questions
Status update
Fast conflict detection

3. CoDesign Phase I Report
Year 2010

4. Motivation Global software engineering
Outsourcing and off-shoring
Software designers are distributed
Communication challenge
Existing technology
SCM tools: CVS, SubVersion
Collaborative IDEs
Modeling tools w/ model merging

5. CoDesign Project Goals
Realtime collaboration from different locations
Modeling-oriented
Extensibility: legacy/domain-specific tools (Infosys)

6. Obstacles of Realtime Collaboration
Latency between designers
“What I see now may not be what you see”
Conflicts occur by unawareness
Synchronization conflicts
Syntactic conflicts
Semantic conflicts
Detection is tricky and expensive

7. Synchronization Conflict
Simple conflicts caused by latency
Can be resolved with little or no human intervention !
Delete Doctorate
Change name to PostDoc 7

8. Conflicts & Inconsistencies
Most researches focus on
Conflicts
Inconsistencies
Conflicts are huge obstacles

9. CoDesign Phase 1 A framework that provides … Delivered
Realtime sync & conflict/inconsistency detection
Extensible collaborative software modeling
Scalability of the size of a model and the number of users
Delivered
High-level categorization and definitions of conflicts
Prototype implementation
Realtime model synchronization
Basic level conflict detection using third party extensions
Publication
Jae young Bang, Daniel Popescu, George Edwards, Nenad Medvidovic, Naveen Kulkarni, Girish M. Rama, and Srinivas Padmanabhuni, “CoDesign – a Highly Extensible Collaborative Software Modeling Framework” at ICSE 2010

10. Generic Modeling Environment
From Vanderbilt University
Software Modeling Tool
Drools
From JBoss Community
Business Logic Integration Platform
Prism-MW
From SoftArch, USC
Lightweight Middleware

11. CoDesign Phase II Progress
Year 2011

12. Research Question (1)
Why is it hard to manage realtime concurrent editing of software models?
Low level of isolation of design decisions
No locking involved
Even locking does not prevent conflicts
Techniques to keep model consistent

13. Research Question (2)
Why do conflicts occur? Any way to prevent them?

14. Life of a Design Decision
Made by a designer
Captured
Encapsulated to be passed
Sent to server
Checked whether it makes conflicts
Broadcasted to designers except the original sender
Decapsulated and applied to the local models
Perceived by designers

15. Research Question (2) Why do conflicts occur? Any way to prevent them?
Latency
No conflict if 0 latency assumed
0 Latency is impossible
Conflict detection is inevitable
Conflict detection increases latency
Parallelization

16. Research Question (3) How frequently should conflict detection be run?
Two cases
Wait for a set of design decisions, run it for all
Run it for every design decision
The later a conflict is found, the higher cost to resolve it
Too intrusive?
Too expensive?

17. Research Question (4)
What is a good granularity of encapsulation of design decisions?
Two extreme cases
Very coarse – group of design decisions
Very fine-grained – atomic design decisions
Event
A design decision made by a designer, encapsulated as a message to be passed between components
Non-atomic events aggravate conflicts

18. CoDesign Phase II Goals
Concurrent collaborative modeling
Parallelized conflict detection
Conflict detection for each atomic event, yet still scalable of the number of designers

19. Definitions (1) Inconsistency Conflict
A contradiction between software design decisions
Conflict
A type of inconsistency
Caused by unawareness between multiple designers
Originated from latency between them

20. Definitions (2) Stable model Consistent model
A model that has been synchronized to every designer so no instance of the model differs from the others
Everyone sees the same on the screens
Consistent model
A model that is stable and has all of its components consistent with each other
A model without any inconsistency

21. Intuition Incoming event queue
Conflict detection does not have to be done in sequence
Can be parallelized
For lowest latency >> less conflicts

22. Fast Conflict Detection: Snapshot Technique
Designers refer to the latest “snapshot”
Run conflict detection against all states that had not been checked until the state was created
It is acceptable the order is reversed – the later events will catch conflicts
* at the stage of formal proof

23. Thank you Please refer to the CoDesign paper: Questions?
Jae young Bang, Daniel Popescu, George Edwards, Nenad Medvidovic, Naveen Kulkarni, Girish M. Rama, and Srinivas Padmanabhuni. CoDesign – A Highly Extensible Collaborative Software Modeling Framework, Proceedings of the 32nd International Conference of Software Engineering (ICSE 2010)
Questions?