Federated search

Federated search is an information retrieval technology that allows the simultaneous search of multiple searchable resources. A user makes a single query request which is distributed to the search engines, databases or other query engines participating in the federation. The federated search then aggregates the results that are received from the search engines for presentation to the user.

This is often a technique to integrate disparate information resources on the web. It can also be a technique to integrate multiple data sources within a large organization or "enterprise."

Federated search came about to meet the need of searching multiple disparate content sources with one query. This allows a user to search multiple databases at once in real time, arrange the results from the various databases into a useful form and then present the results to the user.

As such, it is an information aggregation, or integration approach - it provides single point access to many information resources, and typically returns the data in a standard or partially homogenized form. Other approaches include constructing an Enterprise data warehouse, Data lake, or Data hub. Federated Search queries many times in many ways (each source is queried separately) where other approaches import and transform data many times, typically in overnight batch processes. Federated search provides a real-time view of all sources (to the extent they are all online and available).

In industrial search engines, such as LinkedIn, federated search is used to personalize vertical preference for ambiguous queries. For instance, when a user issues a query like "machine learning" on LinkedIn, he or she could mean to search for people with machine learning skill, jobs requiring machine learning skill or content about the topic. In such cases, federated search could exploit user intent (e.g., hiring, job seeking or content consuming) to personalize the vertical order for each individual user.

As described by Peter Jacso (2004), federated searching consists of (1) transforming a query and broadcasting it to a group of disparate databases or other web resources, with the appropriate syntax, (2) merging the results collected from the databases, (3) presenting them in a succinct and unified format with minimal duplication, and (4) providing a means, performed either automatically or by the portal user, to sort the merged result set.

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