Instead of adding resources into a folder by specifying a list of identifiers, client applications add resources to a folder by specifying a search query that matches the resources to be added. The virtual folder is, therefore, a collection of search queries rather than a collection of resource identifiers. This allows the data archive systems to easily store folder information in a database. A client application can then search by specifying the folder as its search criteria to list all content associated with the folder. Additionally, to ensure that the list of results associated with a particular query does not change after the query is added into a folder, the data archive system also captures generation information associated with the particular query (i.e., the iteration of the search indexes at the time the query is received) and stores the generation information with the query as part of the folder.