Antone Roundy write:
If creation time is relevant to the data being searched, then this makes sense. But what if I want to subscribe to the top 10 Google results for some keywords I'm trying to optimize my site for (ignoring the fact that Google doesn't return search results in any feed format right now)?
That kind of search would be best implemented as a non-incremental feed. To me it sounds exactly the same as a "Top 10" movie list.
Or what about alternative sort orders which are available on sites like Feedster, Google News, etc.? (You can sort by relevance rather than date--the date still has some weight, but the results aren't strictly in date order).
Personally I would still implement this as an incremental feed (new results being added to the top of the feed). If you want an alternative order then you can make use of something like the rank extension that James was proposing.
I really don't see any other way that something like this could be implemented unless you included every single search result whenever the feed was refreshed. For example, let say you have a feed with a limit of 10 items. A new search result is discovered that needs to be sorted (for whatever reason) to the bottom of the list (i.e. position 11). How do you go about informing the user of this new result short of growing the feed to include 11 items?
Adding a second page to your search results is not a feasible option. You can't expect an aggregator to retrieve the full list of pages every time it refreshes just on the off chance that something new was inserted way down at the bottom of the list.
How about Amazon.com affiliates who want to use an RSS parser to display affiliates links to "best sellers" search results? There are a lot of search use cases that don't fit the incremental model.
True. I'm not disputing that. I'm just saying that a many (most?) searches can be implemented with the incremental model and those that can't can usually be implemented with a "top 10" non-incremental model.
All that said, search results are often a bit different than "top 10" lists and the like. With search results, you often don't want to view the contents of the feed in order all at once--the first time you do, but after that, you may just want to see new things as they make it up into the top positions.
This still looks like the incremental model to me. The fact that the initial results aren't in date order doesn't matter from a processing point of view. All that matters is that new results are added to the top of the list.
Regards James
