Search engine. The BioModels Database search engine processes three different types of data in order to provide an accurate result. First, it searches the annotations (by querying the internal database), then the models (using Lucene), and finally, data linked from external resources. Searching for the last is accomplished via direct connection to remote databases and by using remote web services. Ultimately, all the results are collected, processed to remove duplicates, then classified based on which branch the models come from, ordered, and finally, returned to the user.