Responds to a GET request to /estimate/[userID]/[itemID] . The results are opaque values which estimate the strength of interaction between a user and item. Higher values mean stronger interaction. This REST endpoint can also compute several estimates at once. Send a GET request to /estimate/[userID]/[itemID1](/[itemID2]/...) . If the user is not known to the model, a javax.ws.rs.core.Response.Status#NOT_FOUND response is generated. If any item is not known, then that entry in the response will be 0. The output are estimates, in the same order as the item IDs. For default CSV output, each line contains one estimate. For JSON output, the result is an array of estimates.