repositories (such as ehow.com, which
lets users contribute and search how-
to articles), Q&A Web sites (such as Ya-
hoo! Answers2), online customer sup-
port systems (such as QUIQ, 22 which
powered Ask Jeeves’ AnswerPoint, a
Yahoo! Answers-like site). Systems
that share structured knowledge (for
example, relational, XML, RDF data)
include Swivel, Many Eyes, Google
Fusion Tables, Google Base, many e-
science Web sites (such as bmrb.wisc.
edu, galaxyzoo.org), and many peer-to-
peer systems developed in the Seman-
tic Web, database, AI, and IR commu-
nities (such as Orchestra8, 27). Swivel, for
example, bills itself as the “YouTube
of structured data,” which lets users
share, query, and visualize census- and
voting data, among others. In general,
sharing systems can be central (such as
You Tube, ehow, Google Fusion Tables,
Swivel) or distributed, in a peer-to-peer
fashion (such as Napster, Orchestra).

A key distinguishing aspect of systems that evaluate, share, or network is that they do not merge user inputs, or do so automatically in relatively simple fashions. For example, evaluation systems typically do not merge textual user reviews. They often merge user inputs such as movie ratings, but do so automatically using some formulas. Similarly, networking systems automatically merge user inputs by adding them as nodes and edges to a social network graph. As a result, users of such systems do not need (and, in fact, often are not allowed) to edit other users’ input.

Building Artifacts: In contrast, systems that let users build artifacts such