9. A system of ranking candidate curation items, the system comprising: a processor implemented at least partially by hardware; and a non-transitory computer-readable medium communicatively coupled to the processor and having computer-executable instructions stored thereon that are executable by the processor to perform operations comprising: receiving a query; extracting a plurality of items from a plurality of curations; calculating, based on the query, a content similarity measurement for each of the extracted plurality of items; extracting, from each of the extracted plurality of items, a plurality of curation-specific features; calculating one or more curation-specific measurements for each of the extracted plurality of items based on the extracted plurality of curation-specific features, the one or more curation-specific measurements being different than the content similarity measurement; ranking each of the extracted plurality of items based on both the content similarity measurement and the one or more curation-specific measurements to generate a plurality of curation item results; searching a plurality of web resources based on the query to generate a plurality of web results; searching a plurality of open education resources based on the query and learning-specific features to generate a plurality of open education resource results; unifying the plurality of web results, the plurality of open education resource results and the plurality of curation item results to generate a plurality of unified results including a plurality of items; receiving a selection of an item from the unified results; and adding the selected item to a curation; wherein the unifying the plurality of web results, the plurality of open education resource results and the plurality of curation item results to generate the plurality of unified results including the plurality of items comprises: extracting N top results from the plurality of open education resource results, and N top results from the plurality of curation item results, where N is a constant; adjusting an open education resource score of each of the N top results from the plurality of open education resource results based on an importance factor of the plurality of open education resource results; adjusting a curation item score of each of the N top results from the plurality of curation item results based on an importance factor of the plurality of curation item results; and merging the N top results from the plurality of open education results with the N top results from the plurality of curation item results to generate merged results, each item in the merged results having a merged score, the merged scores of the items in the merged results being based on the corresponding adjusted open education resource scores and the corresponding adjusted curation item scores, wherein the plurality of unified results include N results from the merged results.
11. The system of claim 9 , the operations further comprising: extracting N top results from the plurality of web results; and boosting the merged score for each item in the merged results that overlaps an item in the N top results of the plurality of web results, wherein the plurality of unified results include N top results of the merged results, the N top results determined based on at least one of the merged and boosted scores of the merged results.