Dr. Elitsa Alexander
• Crowdsourcing system enlists a crowd of humans to help solve a problem
defined by the system owners
• Compared to the physical world, the Web can dramatically improve existing CS
systems and give birth to novel systems types.
• The web is unique in that it can help recruit a large number of users, enable a
high degree of automation, and provide a large set of social software
4 Key Challenges for CS systems
How to recruit
Nine dimensions of CS systems. The middle four refer respectively to how a CS
system solves the four fundamental challenges.
Degree of Manual
How to Recruit
and Retain Users
Role of Human
Nature of Collaboration
Standalone vs Piggyback
How to Combine
Type of Target Problem
Crowdsourcing is expected to grow rapidly in the near future in three major
• More Generic Platforms: the race is now on to move beyond building
individual systems, toward building general CS platforms.
• More Application and Structure: CS to be applied to ever more classes of
• More Users and Complex Contributions: engage ever broader range of users
and to enable them to make increasingly complex contributions.