A Protocol for Scalable Group and Public Annotations

URL for paper:

http://union.ncsa.uiuc.edu/~liberte/www/scalable-annotations.html

URL for slides:

http://union.ncsa.uiuc.edu/~liberte/www/scalable-annotations-slides.html

Overview

• What are Annotations?

• What is Scalability?

• Is the Web Scalable?

• What are the Scalable Annotation Issues?

• What is Our Solution?

• What is the Annotation Protocol?

• Other attempts at Scalable Annotations?

• How do users find out What is New?

What are Annotations?

What is Scalability?

1 Server, N Clients

N/k Server, N Clients

Number of Readers vs Number of Documents

Our Solution

• Document server tells client where the public annotation servers are.

• User tells client where the group annotation servers are.

• For greater scalability, clients should cache:
  • The location of the public annotation server for a document

  • The known annotations for a document

  • The content of annotations

• Must eventually expire or archive annotations.

The Protocol

More clients and servers

Other Attempts and Scalable Annotations

• Usenet News
  • Post annotations to Usenet newsgroups

  • Post just URLs

  • Usenet goes too far - more resources used for less useful info

• Other centralized "bulletin boards" on the WWW:
  • HyperNews
  • WIT
  • HotWired
  • National Performance Review Electronic Open Meeting

How do readers find out What is New?

• Busy readers want just the useful news.

• Polling - clients ask servers for what is new.
  • Filtering by date, on the server.

  • Clients could automatically poll several servers.

  • Not scalable with many readers.

• Notification - servers tell clients what is new.
  • Server only notifies when there is something new.

  • Email list per document, or annotation subtree.

  • Via usenet group, per document or subject.

  • Need hybrid: distribute load onto only those nodes that forward to interested readers.