In computing, a virtual folder generally denotes an organizing principle for files that is not dependent on location in a hierarchical directory tree. Instead, it consists of software that coalesces results from a data store, which may be a database or a custom index, and presents them visually in the format in which folder views are presented. A virtual folder can be thought of as a view that lists all files tagged with a certain tag, and thus a simulation of a folder whose dynamic contents can be assembled on the fly, when requested. It is related in concept to several other topics in computer science, with names including saved search, saved query, and filtering.
Technology
Documents cannot be "stored" in a virtual folder, since physically a virtual folder is just a file storing a search query. Any attempt to store a file in a virtual folder, depending on the implementation, is redirected to some physical store.
Most implementations speed up searching by pre-indexing the hard drive, or the locations where the search has to be performed. So when searching is to be done, the index, which is a representation of the entire data suitable for fast searching, is used. Since the entire folder hierarchy is not accessed, the search is completed much faster.
Implementations
History
BeOS
When a user performs a file search, a file is created in the folder "/boot/home/queries" with a name derived from the content of the query and the date and time of the search, such as "Name = Western Infirmary - Mar 21, 11:59:40 PM". The query criteria of the search is stored in an attribute of the file called "qrystr". When the file is opened, the filesystem indexes were queried and a Tracker window is opened with an up-to-date list of files that match the criteria.
Additional features were added to search with subsequent releases. Release 2 introduced the ability to edit saved queries, and Release 3 gave the users the chance to define their own names for saved queries. Before Release 4 in 1998, all queries were stored indefinitely. However, with R4, the BeOS developers introduced a seven-day limit on all queries. If a user wanted a query to stay around longer, they could uncheck a "Temporary" flag in the Find dialog.
macOS
Dominic Giampaolo, one of the lead developers of the BeOS filesystem, was also involved in adding a virtual folder system in Apple Inc.'s macOS operating system.
There are many variants of the Smart Folder concept that can be seen in applications that use the Spotlight engine, usually identified by a gear symbol on a purple-hued icon. Examples include: Smart Mailboxes in Mail and Smart Groups in Address Book.
Before Spotlight earlier versions of macOS had a similar concept in the iApps (iTunes and iPhoto), but these did not use the system-wide Spotlight engine.
Microsoft Windows
Saved Searches
By default, Windows Vista references the disk partition and user profile of a created Saved Search as part of its scope, which inhibits their ability to return content from different machines or partitions when transferred to other machines. Microsoft released a SearchMelt Creator utility that changes the scope of Saved Searches to reference the %USERPROFILE% environment variable, which allows them to operate on other machines or profiles; users can also edit Saved Searches manually to reference %USERPROFILE% to facilitate sharing.
Saved Searches additionally allow users to create stacks of data, which are collections of items assembled by properties such as document authors. The same content can appear in more than one stack. Users can, by way of example, first navigate to a specific author stack then to a keyword stack, or to the same keyword stack and to the same author stack without creating new folders or changing the underlying location on disk, which frees users from the limitation of a hierarchical folder structure where one item can only be stored in one location — this liberation from folder hierarchies was a primary benefit and differentiator of WinFS.
Pre-release builds of Windows Vista offered significantly different metadata and namespace functionality in contrast to the functionality of the build of Windows Vista released to manufacturing. Microsoft constructed several Saved Searches as part of its goals for a new user profile namespace, which replaced traditional Special Folders. My Documents, My Music, and My Pictures on the Start menu were replaced by Saved Searches — All Documents, All Music, and All Pictures and Videos — that searched for documents, music, and photos and videos, respectively, with several other Saved Searches for specific content (e.g., authors for documents) also displayed in the navigation pane of Windows Explorer. When viewing All Music or traditional folders with music, for example, the navigation pane would include Saved Searches for all music, albums, artists, genres, favorite music, and ratings. Stacks in Saved Searches in pre-release builds of Windows Vista could also be created by users, or write properties to data by drag-and-drop — in a feature known as metadata painting, dragging a document onto an author stack, for example, would assign that author to the document. In later builds, Microsoft replaced these Saved Searches with a single Library Saved Search that aggregated content from all locations with subqueries for individual types (e.g., the Music Library searched Library for all music). Microsoft had sought to include metadata painting and user profile namespace virtual folders since the development of WinFS; the objective was for Saved Searches to become the primary way users interact with data. Microsoft reportedly received extensive feedback that these changes were confusing — having Saved Searches in the new user profile namespace caused users to believe there were several folders with similar names.
Accordingly, Microsoft removed the Library Saved Search and its associated subqueries; however, Windows Vista still includes Recent Documents, Recent E-mail, Recent Music, Recent Pictures and Videos, and Recently Changed Saved Searches, all of which use a single Indexed Locations Saved Search in accordance with the previous Library concept. These Saved Searches were previously known as Last 30 Days Documents, Last 7 Days Email, Fresh Tracks, and Last 30 Days Pictures and Videos.
Libraries
GNOME
Other implementations
Email clients
Music clients
See also
- Features new to Windows Vista
- WinFS
Notes
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