More links: integrate with other content and across sites

The first easily apparent feature which trackback brings is automatic cross-linking with other sites. For instance, if a link to a trackback-compliant site is added to a discussion item, the target site will link back to the discussion. If an offisite blogger writes about a piece of content or discussion on our sites, a link to their entry will appear on our site. This makes it quite easy to carry on discussions and annotations distributed across our own sites, and opens up many potential integrations with other platforms.

Richer branching: non-hierarchical discussion branching and linkage

One of the crucial problems with threaded discussion forums - as our more sophisticated users often point out - is that they branch like simple trees, whereas rich discussions branch in more complex ways. Discusion forums' structure is based on the historical accident of the 'reply' gesture as much as by the dynamic of discussion. For instance, we have repeatedly received the following feature request: user A posts a discussion item which touches on several issues; user B has something to say which is inspired by one of the issues in user A's post, but is not properly a thread from it - user B wants to create a new discussion (raise a new issue etc) which is spawned from user A's post but has a distinct life separate from it.

By offering trackback-enabled methods for spawning new posts which link back to a discussion item (or other piece of content), we can take a large step towards meeting that feature request. For instance, instead of replying to a discussion item, a user might 'blog this' item (spawning a new entry in her blog which is two-way linked with it), or might spawn a new discussion topic (or issue, etc - we will also explore 'typing' of posts), find a suitable location for it to be added in the site, and thus make a new discussion which two-way links to the previous one. As a bonus, this can be made to work across sites as well! (In passing, I note that this approach does not solve another issue we've been eager to be able to branch discussion on - internal structure within a long discussion item. At some point in the future, we'll explore using trackbacks to a specific bit of sub-content rather than an entire post ordocument.)

See figures 1 and 2 for some graphical treatments of non-hierarchical branching.

Multiple contexts: combine the transparency of blog-view with the focus of threaded discussions

By allowing a piece of content to be 'both' a part of a discussion thread 'and' an independent topic or blog post, we can explore having the same content made salient in different contexts for different purposes. In fact, combining this with repository views and possible offsite trackbacks, we can start to explore rich ways of re-using content and widening discussion.

Sharing categories: associate metadata with content in an open manner

By basing the association of metadata with content on trackback, we can enable a cross-site, and even cross-system metadata system. This would be especially useful for maintaining large-scale vocabularies, taxonomies and bibliographic databases.

Relating content: associate content items in an open manner

Trackback can also be used to make explicit 'this is related to that' gestures between two items of content.