Branch file
Sidecar files (English sidecar files , buddy files or connected files ) are files that related to another file data store (often metadata ) that the file format is not supported the main file.
One or more branch files can be created for each original file. This is in contrast to metadata databases, in which a database contains metadata about several original files.
In most cases, the relationship between the original and the branch file is established via the file name; Subsidiary files have the same base file name as the original file, with a different ending . One problem with this system is that most operating systems and file managers are unaware of these relationships and let the user rename or move individual files, which breaks the relationship.
Examples
- Amiga hunk metadata
- Under AmigaOS , a file with an
.infoextension contains metadata for an associated executable Amiga Hunk file. - Extensible Metadata Platform (XMP)
- XMP metadata is stored in a branch file if either a file format does not support the embedding of XMP metadata or if the workflow requires it.
- Linked web files and folders
- A filesystem object that associates two or more files. The file system treats linked files as one unit when moving, copying, and deleting. Some versions of Internet Explorer and Microsoft Word can save an HTML file and its associated resources as such a unit.
- THM
- Many digital cameras store a JFIF -coded preview image file next to a recorded video with the file name extension
.thm(from English "thumbnail") and the same main file name as the video. This procedure enables the quick display of a still image preview of the video and the saving of camera data which are not supported by the AVI file format. - JPEG + WAV
- Some digital cameras allow voice / audio annotations on photos. These are saved as WAV audio files with the same basic file name as the JPEG image file.
- Meta Information Encapsulation (MIE)
- The MIE format is an expandable, dedicated metadata format part of ExifTool . MIE branch files can be used to encapsulate metadata from a variety of sources and bundle it together with any other file type.
A variant of this are copies of the original file, which contain largely the same information, but in a different format or from an earlier version:
- Exif
- Since many JPEG editing software used to destroy Exif metadata stored in digital photos, some photo cataloging applications allow the Exif data to be extracted and saved in an .exf file so that the metadata can later be reinserted in the JPEG file.
- Raw data + JPEG
- Many digital cameras allow uncompressed raw data and a JFIF -coded image file to be saved simultaneously when shooting in raw data mode. This allows a faster preview of the photo and support from applications that do not support the (often undocumented) raw data format.
- XMP
- Darktable uses both XMP branch files and a fast database to store metadata and edit settings. On Windows i. d. As a rule, the filename extension of the original file is removed to form the name of the XMP branch file, which leads to conflicts as soon as original files with the same base name but different filename extensions are in the same directory.
Alternatives
Instead of storing data separately, it can be stored as part of the main file. This is especially done with container files, in which several types of data can be stored. Instead of having separate files in the file system, multiple files can be grouped into an archive file that holds them together, but requires software to process the archive file rather than individual files. This is a general solution because archive files can contain any files from the file system.
Alternative data streams
One solution to this problem at the file system level is to use alternative data streams that allow multiple pieces of information to be linked to a single file. Branch files can be seen as alternate data streams for file systems without native support for them.
Alternative data streams can be processed with common file system tools: because the support is built into the operating system, they are not displayed as separate files and all applications inherit support for them. However, alternate data streams cannot be copied to file systems without support for it, or transmitted over a channel that does not support alternate data streams. Instead, alternative data streams are usually stored as a branch file for data exchange.
Mac OS and OS X are major examples of operating systems that support alternative data streams, known as resource forks in the HFS file system. However, this causes problems when exchanging data via CD-ROMs in ISO-9660 format, FAT -formatted MS-DOS disks and via e-mail and requires the use of subsidiary files to store this information.