| Collaboration

Locks, Leases and Lost Updates

See Also:

• Locking and notification in DesignIssues
• HTTP Derived-From/Version mechanism
• WWW4 authoring tools breakout
• LINCKS parallel editing
• Khhare's paper on locking, fairness, etc

The Lost Update Problem

1. Joe GETs version 1.1
2. Bill GETs version 1.1
3. Joe writes version 1.2
4. Bill writes version 1.3, overwriting Joe's edits

Levels of Solution

1. No mechanism
2. Detection: error at step 4
3. Prevention: warning/error at step 2
4. Fairness: guarantee progress