GRAMPS and XML
GRAMPS is capable of importing and exporting an XML file that contains all the information in the database. This file is useful for transferring data from one machine to another or for XML processing.
The easiest way to generate an XML file is to export the data. This can be done from the File->Export menu. This will generate a file with a .gramps extension. This file is usually a gzip'd XML file (depending on some system settings, sometimes this will be an uncompressed XML file).
GRAMPS compresses the file because XML files can become rather large. For large databases, this file could grow to 10s to 100s of megabytes in size. Fortunately, XML files compress nicely, usually producing a fairly small size.
How do I tell if the XML file is compressed?
The easiest way is to run the file command on it.
$ file data.gramps
If the file is compressed, you should see a result similar to:
data.gramps: gzip compressed data, from Unix, last modified: Sun Jun 17 22:36:04 2007
If it is uncompressed, you should see a result similar to:
data.gramps: XML 1.0 document text
How do I uncompress the file?
If the file is compressed, you can uncompress it using the gunzip command.
$ gunzip < data.gramps > data.xml
This example creates an uncompressed data.xml file from the compressed data.gramps file.
You must use the I/O redirection operators (">" and "<"), since gzip expects files to have a .gz extension.
Why doesn't GRAMPS just use a .gz extension?
GRAMPS uses the Shared Mime System defined by Free Desktop project, and used by all major desktops, including KDE and GNOME. GRAMPS relies on the MIME type identified by the Shared Mime System to determine the file type of the file.
The Share Mime System allows you to identify a file's type by either using a file extension or by looking at the contents of a small section of the file. If we looked at the contents, we would not be able to tell the difference between a gzip'd GRAMPS XML file or any other gzip'd file. If we looked at uncompressed data, we would not be able to tell the difference between a GRAMPS XML file an any other XML file. For this reason, we must rely on the .gramps extension.
If the GRAMPS XML file had added .gz extension to the name, the Shared Mime system would tell us that the file's type is application/x-gzip instead of the expected application/x-gramps-xml. Unfortunately, it cannot tell us that it is a gzip'd GRAMPS XML file. So, we would not be able to tell if this was a valid file. Even worse, the mime type of application/x-gzip would be associated with another application (such as File Roller or Ark) instead of GRAMPS.
GRAMPS is not unique in this problem. For example, the OpenDocument format used by OpenOffice, KWord and AbiWord is actually a collection of files in a zip archive. If you run unzip on a OpenDocument file, you will see something like:
$ unzip test.odt Archive: test.odt inflating: mimetype inflating: meta.xml inflating: settings.xml inflating: META-INF/manifest.xml inflating: styles.xml inflating: content.xml