I am developing an app that makes use of the Google Books API. One of the features is to sort books by title. I am aware of the restrictions on keeping permanent copies of the data retrieved from any APIs as stated here - https://developers.google.com/terms/#e_prohibitions_on_content. However, is it possible to only keep the id as a reference to that object and the title for sorting. Keep in mind that to view any book details, I will still query the Google Books API.
The book ID and the title are obviously Google's content, however meta you may consider them to be, and such storage of content is against the TOS. In addition, you are building a database of IDs and titles, Google's content, which is against the TOS.