Advanced Suggest-As-You-Type With Solr by John Berryman.
From the post:
In my previous post, I talked about implementing Search-As-You-Type using Solr. In this post I’ll cover a closely related functionality called Suggest-As-You-Type.
Here’s the use case: A user comes to your search-driven website to find something. And it is your goal to be as helpful as possible. Part of this is by making term suggestions as they type. When you make these suggestions, it is critical to make sure that your suggestion leads to search results. If you make a suggestion of a word just because it is somewhere in your index, but it is inconsistent with the other terms that the user has typed, then the user is going to get a results page full of white space and you’re going to get another dissatisfied customer!
A lot of search teams jump at the Solr suggester component because, after all, this is what it was built for. However I haven’t found a way to configure the suggester so that it suggests only completions that that correspond to search results. Rather, it is based upon a dictionary lookup that is agnostic of what the user is currently searching for. (Please someone tell me if I’m wrong!) In any case, getting the suggester working takes a bit of configuration. — Why not use a solution that is based upon the normal, out-of-the-box Solr setup. Here’s how:
Topic map authoring is what jumps to my mind as a use case for suggest-as-you-type. Particularly if you use fields for particular types of topics, making the suggestions more focused and manageable.
Good for search as well, for the same reasons.
John offers several cautions near the end of his post, but the final one is quite amusing:
Inappropriate Content: Be very cautious about content of the fields being used for suggestions. For instance, if the content has misspellings, so will the suggestions. And don’t include user comments unless you want to endorse their opinions and choice of language as your search suggestions!
I don’t think of auto-suggestions as “endorsing” anything. Purely mechanical assistance to assist the user.
If some term or opinion offends a user, they don’t have to choose it to follow.
At least in my view, technology should not be used to build intellectual tombs for users. Intellectual tombs that protect them from thoughts or expressions different from their own.