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

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

 CoDesign Phase I Report Year

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 4

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

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 6

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

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

CoDesign Phase 1  A framework that provides …  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

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

 CoDesign Phase II Progress Year

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 12

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

Life of a Design Decision 1. Made by a designer 2. Captured 3. Encapsulated to be passed 4. Sent to server 5. Checked whether it makes conflicts 6. Broadcasted to designers except the original sender 7. Decapsulated and applied to the local models 8. Perceived by designers 14

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 15

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? 16

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 17

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

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

Definitions (2)  Stable 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 20

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

Fast Conflict Detection: Snapshot Technique 22 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

Thank you  Please refer to the CoDesign paper:  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 32 nd International Conference of Software Engineering (ICSE 2010)  Questions? 23