Preservation planning¶

Formats¶

In the FPR, a “format” is a record representing one or more related format versions, which are records representing a specific file format. For example, the format record for “Graphics Interchange Format” (GIF) is comprised of format versions for both GIF 1987a and 1989a.

When creating a new format version, the following fields are available:

• Description (required) - Text describing the format. This will be saved in METS files.
• Version (required) - The version number for this specific format version (not the FPR record). For example, for Adobe Illustrator 14 .ai files, you might choose “14”.
• PRONOM ID - The specific format version’s unique identifier in PRONOM, the UK National Archives’s format registry. This is optional, but highly recommended. Many identification and characterization tools, use PRONOM ID’s to recognize formats.
• Access format and Preservation format - Indicates whether this format is suitable as an access format for end users, and for preservation.

When a new version of Archivematica is released, typically new formats are added from recent releases of PRONOM.

Groups¶

A format group is a convenient grouping of related file formats which share common properties. For instance, the FPR includes an “Image (raster)” group which contains format records for GIF, JPEG, and PNG. Each format can belong to one (and only one) format group.

The following format groups come pre-populated in the FPR:

• Audio
• Binary (Data)
• Binary (Executable)
• CAD
• Data Visualization
• Database
• Dataset
• Desktop Publishing
• Disk Image
• Email
• Flash
• Font
• GIS
• Image (Raster)
• Image (Vector)
• Package
• Portable Document Format
• Presentation
• Spreadsheet
• Statistics
• Text (Markup)
• Text (Plain)
• Text (Source Code)
• Test (Structured)
• Unknown
• Video
• Word Processing

The groups as determined by Artefactual should be perceived as arbritrary and are simply meant to make the Format Policy Registry easier to read and navigate. If an institution so desired, they could change the names and population of the groups in their local Preservation planning tab.

Format policy rules and commands¶

Throughout the FPR, Format policy rules allow commands to be associated with specific file types. For example, in the case of Normalization rules, this allows you to configure the command that uses ImageMagick to create thumbnails to be run on .gif and .jpeg files, while selecting a different command to be run on .png files.

When creating a format policy rule, the following mandatory fields must be filled out:

• Purpose - Allows Archivematica to distinguish rules that should be used to normalize for preservation, normalize for access, to extract information, etc.
• Format - The file format the associated command should be selected for.
• Command - The specific command to call when this rule is used.

Identification¶

Tools

The identification tool properties in Archivematica control the ways in which Archivematica identifies files and associates them with the FPR’s version records. The current version of the FPR server contains three tools: the Open Preservation Foundation’s Fido tool, which identifies based on the IDs in PRONOM; a simple script which identifies files by their file extension; and Siegfried which like Fido, is based on PRONOM ID and provides detailed information on the basis for format matches in its output. You can use the identification tools portion of FPR to customize the behaviour of the existing tools, or to write your own.

Rules

Identification rules allow you to define the relationship between the output created by an identification tool, and one of the formats which exists in the FPR.

Identification rules are necessary only if identifying files by extension- if using either Fido or Siegfried, the tool will do the identification based on PUID.

Commands

Identification commands contain the actual code that a tool will run when identifying a file. This command will be run on every file in a transfer.

Format policy registry tools¶

This is a list of the tools in use by Archivematica for the various preservation tasks being managed by the FPR. To add a new tool, see Altering rules and commands below.

Characterization¶

Characterization is the process of producing technical metadata for an object. Archivematica’s characterization aims both to document the object’s significant properties and to extract technical metadata contained within the object.

Rules

This lists the characterization commands associated with various formats. Note that formats that are not listed will be characterized by FITS by default.

Commands

Output from characterization commands is expected to be valid XML, and will be included in the AIP’s METS document within the file’s <objectCharacteristicsExtension> element. Tools supported by default are:

Default

The default characterization tool is FITS; it will be used if no specific characterization rule exists for the file being scanned.

It is possible to create new default characterization commands, which can either replace FITS or run alongside it on every file.

Multimedia

If using Archivematica’s default commands, all three of these tools are run on multimedia files:

• FFprobe, a characterization tool built on top of the

  same core as FFmpeg, the normalization software used by Archivematica

• MediaInfo, a characterization tool

  oriented towards audio and video data

• ExifTool, a

  characterization tool oriented towards still image data and extraction of embedded metadata

Disk images

The fiwalk command from Sleuthkit is used for characterization of disk image formats.

Event Detail¶

Event detail ensures that information about the software running a command is written to the METS file as the “event detail” property.

Rules

Rules are not required for Event detail, only commands.

Commands

The commands describe the event detail output written to the METS file when using various FPR commands; typically, the name and version of the tool being used.

Extraction¶

Extraction refers to the extraction of content from package formats, such as disk images and various zip formats.

Rules

This lists the extraction commands associated with various formats.

Commands

Archivematica by default supports three extraction commands- 7zip, for most 7zip compatible formats, unrar-free, for RAR formats, and Sleuthkit, for many disk image formats.

Normalization¶

Normalization rules determine how Archivematica will handle the creation of access and preservation copies during the Ingest of packages.

Rules

This lists the normalization (format conversion) commands associated with various formats. Normalization rules have three purposes: Access, for use in the DIP, Preservation, for use in the AIP, and Thumbnail, for use in both the AIP and DIP. You may only have one normalization rule per format per purpose.

The success rate of each normalization rule is show in the “Success” column.

Commands

Archivematica by default has 15 normalization commands, some of which use Archivematica-specific scripts, the rest of which use tools such as ImageMagick (convert command), Ghostscript, Inkscape, ps2pdf and ffmpeg.

Transcription¶

Transcription runs an OCR tool on image files which contain text.

Rules

This lists the transcription commands associated with various formats.

Commands

By default, Archivematica supports one transcription command, which uses the OCR tool Tesseract.

Validation¶

Format validation ensures that files are well-formed and compliant with any relevant format specifications.

File validation can also be used to create institution-specific policies for multimedia using the MediaConch tool.

Rules

This lists the commands associated with validating various formats.

Commands

Archivematica by default supports two tools for validation: JHOVE, which is used on a wide variety of formats, and MediaConch which is used to validate Matroska (mkv) files. MediaConch can also be used to create custom validation commands which check files against a local policy on a variety of multimedia formats. These policy checks can be performed on originals, preservation derivatives and access derivatives. For more information please see: MediaConch workflow.

Verification¶

Verification is run after normalization commands. Archivematica will run two commands: one checks if a file exists, and the other checks if the file exists and is greater than 0 bytes in size.

Verification is run on the output of normalization, not on the original file.

Identification commands¶

Identification commands are very simple to write, though they require some familiarity with Unix scripting.

An identification command run once for every file in a transfer. It will be passed a single argument (the path to the file to identify), and no switches.

On success, a command should:

• Print the identifier to stdout
• Exit 0

On failure, a command should:

• Print nothing to stdout
• Exit non-zero (Archivematica does not assign special significance to non-zero exit codes)

A command can print anything to stderr on success or error, but this is purely informational - Archivematica won’t do anything special with it. Anything printed to stderr by the command will be shown to the user in the Archivematica dashboard’s detailed tool output page. You should print any useful error output to stderr if identification fails, but you can also print any useful extra information to stderr if identification succeeds.

Here’s a very simple Python script that identifies files by their file extension:

import os.path, sys
(_, extension) = os.path.splitext(sys.argv[1])
if len(extension) == 0:
        exit(1)
else:
        print extension.lower()

Here’s a more complex Python example, which uses Exiftool’s XML output to return the MIME type of a file:

#!/usr/bin/env python

from lxml import etree
import subprocess
import sys

try:
    xml = subprocess.check_output(['exiftool', '-X', sys.argv[1]])
    doc = etree.fromstring(xml)
    print doc.find('.//{http://ns.exiftool.ca/File/1.0/}MIMEType').text
except Exception as e:
    print >> sys.stderr, e
    exit(1)

Once you’ve written an identification command, you can register it in the FPR using the following steps:

1. Navigate to the “Preservation Planning” tab in the Archivematica dashboard.
2. Navigate to the “Identification Tools” page, and click “Create New Tool”.
3. Fill out the name of the tool and the version number of the tool in use. In our example, this would be “exiftool” and “9.37”.
4. Click “Create”.

Next, create a record for the command itself:

1. Click “Create New Command”.
2. Select your tool from the “Tool” dropdown box.
3. Fill out the Identifier with text to describe to a user what this tool does. For instance, we might choose “Identify MIME-type using Exiftool”.
4. Select the appropriate script type - in this case, “Python Script”.
5. Enter the source code for your script in the “Command” box.
6. Click “Create Command”.

Finally, you must create rules which associate the possible outputs of your tool with the FPR’s format records. This needs to be done once for every supported format; we’ll show it with MP3, as an example.

1. Navigate to the “Identification Rules” page, and click “Create New Rule”.
2. Choose the appropriate foramt from the Format dropdown - in our case, “Audio: MPEG Audio: MPEG 1/2 Audio Layer 3”.
3. Choose your command from the Command dropdown.
4. Enter the text your command will output when it identifies this format. For example, when our Exiftool command identifies an MP3 file, it will output “audio/mpeg”.
5. Click “Create”.

Once this is complete, any new transfers you create will be able to use your new tool in the identification step.

Normalization Commands¶

The goal of a normalization command is to take an input file and transform it into a new format. For instance, Archivematica provides commands to transform video content into FFV1 for preservation, and into H.264 for access.

Archivematica provides several parameters specifying input and output filenames and other useful information. Several of the most common are shown in the examples below; a more complete list is in a later section of the documentation: Normalization command variables and arguments.

When writing a bash script or a command line, you can reference the variables directly in your code, like this:

inkscape -z "%fileFullName%" --export-pdf="%outputDirectory%%prefix%%fileName%%postfix%.pdf"

When writing a script in Python or other languages, the values will be passed to your script as commandline options, which you will need to parse. The following script provides an example using the argparse module that comes with Python:

import argparse
import subprocess

parser = argparse.ArgumentParser()

parser.add_argument('--file-full-name', dest='filename')
parser.add_argument('--output-file-name', dest='output')
parsed, _ = parser.parse_known_args()
args = [
    'ffmpeg', '-vsync', 'passthrough',
    '-i', parsed.filename,
    '-map', '0:v', '-map', '0:a',
    '-vcodec', 'ffv1', '-g', '1',
    '-acodec', 'pcm_s16le',
    parsed.output+'.mkv'
]

subprocess.call(args)

Once you’ve created a command, the process of registering it is similar to creating a new identification tool. The folling examples will use the Python normalization script above.

First, create a new tool record:

1. Navigate to the “Preservation Planning” tab in the Archivematica dashboard.
2. Navigate to the “Identification Tools” page, and click “Create New Tool”.
3. Fill out the name of the tool and the version number of the tool in use. In our example, this would be “exiftool” and “9.37”.
4. Click “Create”.

Next, create a record for your new command:

1. Click “Create New Tool Command”.
2. Fill out the Description with text to describe to a user what this tool does. For instance, we might choose “Normalize to mkv using ffmpeg”.
3. Enter the source for your command in the Command textbox.
4. Select the appropriate script type - in this case, “Python Script”.
5. Select the appropriate output format from the dropdown. This indicates to Archivematica what kind of file this command will produce. In this case, choose “Video: Matroska: Generic MKV”.
6. Enter the location the video will be saved to, using the script variables. You can usually use the %outputFileName% variable, and add the file extension - in this case %outputFileName%.mkv
7. Select a verification command. Archivematica will try to use this tool to ensure that the file your command created works. Archivematica ships with two simple tools, which test whether the file exists and whether it’s larger than 0 bytes, but you can create new commands that perform more complicated verifications.
8. Finally, choose a command to produce the “Event detail” text that will be written in the section of the METS file covering the normalization event. Archivematica already includes a suitable command for ffmpeg, but you can also create a custom command.
9. Click “Create command”.

Finally, you must create rules which will associate your command with the formats it should run on.

Normalization command variables and arguments¶

The following variables and arguments control the behaviour of format policy command scripts.

Extraction commands¶

An extraction command is passed two arguments: the file to extract, and the path to which the package should be extracted. Similar to normalization commands, these arguments will be interpolated directly into bashScript and command scripts, and passed as positional arguments to pythonScript and asIs scripts.

Here’s a simple example of how to call an existing tool (7-zip) without any extra logic:

7z x -bd -o"%outputDirectory%" "%inputFile%"

This Python script example is more complex, and attempts to determine whether any files were extracted in order to determine whether to exit 0 or 1 (and report success or failure):

from __future__ import print_function
import re
import subprocess
import sys

def extract(package, outdir):
    # -a extracts only allocated files; we're not capturing unallocated files
    try:
        process = subprocess.Popen(['tsk_recover', package, '-a', outdir],
            stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
        stdout, stderr = process.communicate()

        match = re.match(r'Files Recovered: (\d+)', stdout.splitlines()[0])
        if match:
            if match.groups()[0] == '0':
                raise Exception('tsk_recover failed to extract any files with the message: {}'.format(stdout))
            else:
                print(stdout)
    except Exception as e:
        return e

    return 0

def main(package, outdir):
    return extract(package, outdir)

if __name__ == '__main__':
    package = sys.argv[1]
    outdir = sys.argv[2]
    sys.exit(main(package, outdir))

Transcription commands¶

Transcription commands are expected to write their data to disk inside the SIP. For commands which perform OCR, metadata can be placed inside the “metadata/OCRfiles” directory inside the SIP; other kinds of transcription should produce files within “metadata”.

For example, the following bash script is used by Archivematica to transcribe images using the Tesseract software:

ocrfiles="%SIPObjectsDirectory%metadata/OCRfiles"
test -d "$ocrfiles" || mkdir -p "$ocrfiles"

tesseract %fileFullName% "$ocrfiles/%fileName%"

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