Storage

Annotation is on same machine as original

Everything can be stored on the same machine. This solution has been adopted by:

• WIT
• HyperNews
• Many others...

Storing everything on the same machine tends to require authentication. If everything is on the same machine, latency tends to be better. This solution is easy to deploy using the existing forms and CGI scripts available with WWW.

Annotation is stored at a proxy server.

With this solution, people funnel all of their documentation requests through a proxy server. The proxy server injects the annotations into the documents as it forwards them back to the client. This solution is quite viable for group annotations, but may have some scalability problems for public annotations. Authentication is needed to support the modification of annotations at the proxy server.

Annotation is stored at the author's machine.

With this solution, the annotation is reached via a hypertext link. Authentication is less of an issue, since the author can directly access a file containing their annotation.

The problem remains, where does the hypertext link get inserted. Two possibilities are:

At the original machine.

The following options exist:

• The original document can be modified to contain the annotation hypertext links. There are many problems with this strategy.
• The NCSA HTTPD <INC> technology can be used to insert the annotations. This will not work for in-line annotations.
• A copy of the original can be made that has all of the annotations in it.
• The annotations can be dynamically inserted into the document at HTTP get time.
  At a proxy server
  If a proxy server is being used, the hypertext link information can be stored at the proxy.