tracking-ISSUE-81: Do we need a response at all from server?

We think the topic of a response to the DNT header will require a fair amount of further discussion.  We think that a number of other issues should be resolved first before we can reach a consensus on whether it should be sent and what it means. Here are some specific concerns:

COST OF IMPLEMENTATION

While most web server environments do make it simple to return a HTTP header as part of the response, integrating a way to return such a header into existing systems isn't necessarily straightforward. Some systems used today to combine web requests with information known about the user to form targeted responses and do not allow for an easy way to derive what opt-ins are in place and why the response is the way it is. A response header that indicates what the service saw in the DNT request AND how it was processed is not always a trivial engineering exercise.

VALUE OF IMPLEMENTATION

Today browsers are consistently moving in the direction of less and less user interface, reducing the number of choices users must make to experience the web, and trying to make smart choices on behalf of the user. It's not immediately obvious that all browser vendors will want to process a DNT response and take any action. Before we can truly evaluate the benefit of a response, we should have a clearer idea of what browser vendors want to do with this information. There is little benefit to the community in requiring online services to invest in being able to return a response if the value is then ignored.

WHEN TO RETURN A RESPONSE

To fully understand the benefit of a response, we need to understand when a response would be required. If we conclude too early that a response is required we run the risk of creating reasons to have some kind of value and potentially making the response more and more complex. Perhaps a good resolution at this point is to agree that nobody believes having a response is detrimental but until we address some of the other questions before us (e.g. first party vs. third party) it will be hard to demonstrate that the cost is worth the benefit.

INCREASED LOAD ON WEB SERVERS

We share Roy's concerns [1] about additional load on servers and content caches.

[1] http://lists.w3.org/Archives/Public/public-tracking/2011Oct/0047.html

JC
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