On August 18, Summon will be releasing an update to its relevance ranking algorithm. Only the ranking of search results will be affected; the number of search results returned for any given query will not be change. The new algorithm is expected to improve mainly the relevance of exploratory search cases, complementing the known item search improvements released earlier this year.

Summary of the improvements:

Two primary improvements in the new ranking algorithm are:

* Improved balance between dynamic and static rank: Summon’s relevance ranking algorithm uses two types of relevance factors: the dynamic rank and the static rank. The dynamic rank factors describe how well a given query matches each record. The static rank factors represent the importance or value of each record. One common type of relevance issues we have observed in the past involve cases where the influence of the dynamic rank is too strong, such that records with low static ranks, such as old publications and less important content types, appear among the top search results. The new algorithm has a better balance of the dynamic rank and the static rank, and it should reduce the number of such issues.

* Improved balance of short titles and long titles in the top results: Previously, Summon’s ranking algorithm tended to emphasize records with short titles, especially those that closely match the query string. The new algorithm reduces the influence of the field length normalization and the exact match boost, and as a result, top search results include a better mix of short and long titles that are relevant to the query.

One noteworthy property of the new algorithm is that short and general topical queries (e.g., linguistics, global warming) tend to return more books, eBooks, references and journals among the top results. And long and specific topical queries (e.g., linguistics universal grammar, global warming Kyoto protocol) tend to return more journal articles among the top results.

Examples
Here are a few examples that demonstrate the improvements. Please note that the search results depend on the content, so these examples may not apply to our instance of Summon.

• dog law => The top results returned by the old algorithm are mostly items titled “Dog Law” and included very old journal and magazine articles. The top results returned by the new algorithm are more balanced, and include more recent titles than the original algorithm, such as “Dangerous dogs law updated” (Journal Article, 2007) and “Animal law and dog behavior” (Book, 1999).
• autism aba therapy for young children => The top results returned by the old algorithm contained many books and other items titled just “Autism”. The top results returned by the new algorithm include longer titles, such as “A step-by-step ABA curriculum for young learners with autism spectrum disorders (age 3-10)” (eBook, 2013).

If you have any questions, concerns or feedback, please send them to the Discovery and Access Working Team (ul-dawt@lists.psu.edu).— Binky Lush