BeOS The initial developer preview of the operating system, released in October 1995, included database-like functionality to make it easier for users to manage their files. To do this the filesystem indexes certain file attributes to allow for fast searching. By default the filesystem indexes the filename, size and last modified timestamp automatically, but could also create indexes for other attributes when told to by either an application or by the user. 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 In April 2005, Apple released
Mac OS X v10.4, with their implementation of virtual folders called
Smart Folders. These folders are dynamically updated by the
Spotlight engine to contain content that match certain criteria. For example, this could be used to give you a folder containing all the
Word documents containing the word "shpadoinkle" that have been edited within the last 7 days. Smart Folders are created by saving a Spotlight search, which records the search criteria in a
Property list file with a
.savedSearch extension and, by default, saves them in the "/Users/username/Library/Saved Searches" folder.
Dominic Giampaolo, one of the lead developers of the BeOS filesystem, was also involved in adding a virtual folder system in
Apple Inc.'s
Mac OS X 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 Windows Vista released in November 2006 introduced virtual folders to the Windows platform with the introduction of
Saved Searches, which present items based on their properties rather than folder hierarchies on disk. Saved Searches are not folders — they do not store items — they instead are
XML files that retain a query for utilization by
Windows Search. When a Saved Search is created, the query retains the presentation layout that appeared when the search was first performed such that subsequent searches will present identical arrangements of items. 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
user profile folders.
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). the objective was for Saved Searches to become the primary way users interact with data.
Libraries Windows 7 introduces
Libraries to display and organize content. Similar to Saved Searches, a Library is an XML file with a unique extension — .library-ms extension — and it is a collection of files organized by specified locations. Unlike Saved Searches, however, users must specify folder locations, and Libraries can display content that does not match the type of the Library (e.g., the Pictures Library may display a document if any subfolders include documents). Libraries have a shell namespace extension in Explorer and their XML files can be reused across Windows installations or the network.
GNOME 2.14In GNOME 2.14, a saved search is a virtual folder whose contents are the result of a
Nautilus search, which has multiple backends. The contents of these folders are determined dynamically when the folder is opened, and updated automatically when files are created or modified.
Other implementations Email clients Virtual folders are also a well-established construct in
email clients. In early 1991, the Emacs-based mail reader
VM provided a virtual folder facility in its version 5.09. VM allows the users to define virtual folders using rules, taking their mail content from one or more physical folders and based on selection criteria dealing with dates, authors, recipient, subject, message body etc. Virtual folders can also be created interactively and take content from previously defined virtual folders, thereby cascading the selection criteria. The
Evolution email client created by
Helix Code in 2000, also incorporated virtual folders. Folders can be created that automatically list e-mails matching user-defined rules, for example all e-mail from a particular address or all e-mail that includes a specific keyword. The
Opera web browser released a new mail client (beta in November 2002, final version in Jan 2003), M2, in which virtual folders (called access points) were used for all email management. Virtual folders were automatically made for active contacts, for attachments and for assigned labels. Virtual folders were also automatically generated whenever a search was performed, and manual virtual folders could use multiple logical mail header rules for their construction (including using
regular expressions).
Microsoft Outlook 2003 added a similar feature called
Search Folders.
Gmail, first released in 2004, bases all of its mail management on virtual folders accessed via labels.
Mozilla Thunderbird also has the ability to create search folders and from version 1.5 allowed the search to be done over more than one email account.
Music clients In July 2002, Apple announced version 3 of
iTunes which includes
Smart Playlists which can be considered a variant of a virtual folder. The only difference is that the search executed on accessing them is not on the file system's folder hierarchy, but on their internal data-store. Microsoft also added a similar feature to version 9 of
Windows Media Player in Windows XP called
Auto Playlists in 2003. == See also ==