While the set of out-of-the-box ranking models might be sufficient for most users, they may not be sufficient in some scenarios. E.g. new search verticals in specific domains. Poor relevance experience in these cases could potentially be addressed by utilizing additional managed properties as inputs into our search ranking function. Doing so currently requires editing and uploading an abstruse XML file, which is a high barrier to entry.
The Ranking Model Tuning app facilitates this by providing UI to select a seed ranking model, add/remove ranking features to/from it, and nominate those features whose contribution to the ranking score needs to be set.
The operations involved in producing this ranking model are unfortunately quite complex. This is partly alleviated by the fact that the target audience (search admins) will be more sophisticated than typical end-users, or even typical admins. We also expect that they will be up for a reasonable investment, such as judging a reasonable number of queries.
Note that some aspects of the functionality provided by this app are known to be incompatible with Internet Explorer 8.