Generally, OOV terms are proper names or newly created
words. For example, a user wants to search the information
about the Influenza A (H1N1) disease in Malaysia by
entering “H1N1 Malaysia” as the query. The H1N1 is a
newly created term and may not be included in a dictionary
which was published only a few years ago. If the term H1N1
is omitted from the query translation, it is most likely that the
user will not get any relevant documents at all.