AIP pointer file

Pointer files have been used to help provide sustainable access to compressed AIPs since Archivematica 1.0. [1]. The documentation about them, below, is currently in progress.

Purpose

Pointer files can help users ascertain information about their AIPs without needing to consult the Storage Service API or database.

As an example, pointer files include:

• Information about compression, currently used internally by Archivematica itself for Re-ingest or unpacking for delivery via the API
• Information about encryption so that AIPs can be recovered if encrypted.
• Information about where the AIP is stored relative to the storage service. NB. there are some variations, see below.

Describing the location of the AIP

Information about the location of an AIP is stored in a

mets:filesec

inside the pointer file:

  <mets:fileSec>
    <mets:fileGrp USE="Archival Information Package">
      <mets:file ID="rs_s3-cc53bf2e-0eb9-4d00-a752-8f07c2886fe9" 
                 GROUPID="Group-cc53bf2e-0eb9-4d00-a752-8f07c2886fe9" 
                 ADMID="amdSec_698926">
        <mets:FLocat xlink:href="/var/archivematica/storage_service/aipstore/cc53/.../ex1-cc53bf2e-0eb9-4d00-a752-8f07c2886fe9.7z" 
                     LOCTYPE="OTHER" OTHERLOCTYPE="SYSTEM"/>
        <mets:transformFile TRANSFORMTYPE="decompression" TRANSFORMORDER="1" TRANSFORMALGORITHM="bzip2"/>
      </mets:file>
    </mets:fileGrp>
  </mets:fileSec>

In some storage options that can be configured via the storage service, such as LOCKSS you will see information about the remote location of the AIP:

 <mets:fileSec>
    <mets:fileGrp USE="Archival Information Package">
      <mets:file ID="FLocatTest-e0ff9a0e-a7f5-4bee-b9c2-7e2321dde7a6">
        <mets:FLocat LOCTYPE="URL" xlink:href="http://lockss1.example.org:8083/ServeContent?url=http://archivematicastorage.example.com/lockssomatic/FLocatTest-e0ff9a0e-a7f5-4bee-b9c2-7e2321dde7a6.7z"/>
        <mets:transformFile TRANSFORMALGORITHM="bzip2" TRANSFORMORDER="1" TRANSFORMTYPE="decompression"/>
      </mets:file>
    </mets:fileGrp>
  </mets:fileSec>

Note: Not all storage options will show the information about the remote location. Either this information isn't as easy to replay to the user, or it is functionality that was beyond the scope of development of a storage adapter at the time. S3 is a current example where the user would see the path as it is shown above:

/var/archivematica/storage_service/aipstore/cc53/.../ex1-cc53bf2e-0eb9-4d00-a752-8f07c2886fe9.7z

and they would need to ascertain for themselves that the location was relative to the S3 location created for use as an package store online.

Accessing a pointer file

Accessing pointer files inside Archivematica can be done by navigating the Dashboard to Archival storage finding a suitable AIP, e.g. at time of writing a compressed AIP, and under Pointer file clicking View. Archivematica will make a call to the Storage Service API to return the file for that AIP. More information can be found about this in the Archivematica documentation under Storing an AIP.

• Storage Service API reference to return a Pointer File

Developer notes

Location of the pointer file inside Storage Service

Pointer files are stored in the Storage Service directories, for example:

 /var/archivematica/storage_service/d5c3/3360/7b92/4a2f/9002/32f5/a143/daaf/pointer.d5c33360-7b92-4a2f-9002-32f5a143daaf.xml

You can see where they are stored looking up the Storage Service database:

select locations_location.uuid, 
       locations_location.relative_path, 
	   locations_location.description, 
       locations_location.purpose
from locations_location
inner join locations_package 
on locations_location.uuid = 
   locations_package.pointer_file_location_id

Additional references

• LOCKSS integration

Sample Pointer Files

• Sample XML Pointer File
• LOCKSS Integration Pointer File

External Links

• Justin Simpson on the structure and purpose of pointer files at Google Groups
• Feature #5159 The original tranche of work resulting in the implementation of pointer files