I've been working on Drupal distributed search for a while now, releasing a beta of the OpenSearch Aggregator as well as a release of the OpenSearch feed module. The aggregator has a friendly UI for setting up any number of sources and the feed contains relevance information from the Drupal search system. Results are also cached on the aggregator for performance reasons.

More information about these modules can be found in my earlier blog posts about OpenSearch.

The ultimate goal however is to set up distributed search for a Bryght client between a network of secure Drupal sites. The searches for logged-in users should include content that is visible to them across all the different Drupal sites.

OpenID is the obvious choice as an identity mechanism for the users, but it does not immediately help us with the authentication. I've written a document after some research that details possible approaches and solutions. Because we're talking about frontier technology here, it seemed best to repost it publicly to sollicit feedback from anyone interested. I could certainly use some extra opinions on this, as it is all very new to me.

I just committed a working version of my new OpenSearch Aggregator module to Drupal Contrib CVS.

OpenSearch is a standard by Amazon which allows you to share search results through RSS. The feeds are valid RSS, they just contain extra meta-data for searching. So, you can use OpenSearch with any RSS reader to set up feeds to track tags or keywords for example.

We also have an OpenSearch client module that provides these feeds, and I just updated it to send search relevance information along. So, you could set up 5 Drupal sites with OpenSearch module, and a sixth site with the OpenSearch aggregator. Now, you can search all 5 sites simultaneously, and get a single, ordered list of global results.

However, because OpenSearch is an open standard, it can be used for anything. Amazon's A9 search already offers media search for example. The possibilities really are endless.

The best part? The OpenSearch Aggregator presents its results through the normal search system. So, if you install the OpenSearch module on top of this, you automatically provide OpenSearch feeds for the aggregated search. In other words, Drupal is now a complete OpenSearch processing suite! There is no other CMS out there that can claim this.

More info is on the Drupal.org project page.

Today I wrote a quick, basic OpenSearch module for Drupal. It implements the Amazon-originating spec for syndication and aggregation of search results.

The interesting part is that OpenSearch builds upon RSS and Atom, which means that the resulting feeds can be used in any news reader. Of course, an OpenSearch-aware reader can interpret the extra information that is present (total number of results, other search pages, search URL syntax, ...).

I've installed the module on Acko.net, so you can give it a try here:
OpenSearch description file (XML)
Search results for the query "Drupal" (RSS)

The module will be available on drupal.org as soon as CVS Contrib is repackaged in a couple of hours, though it will require Drupal CVS HEAD or 4.7-HEAD to work.