Old version of this page: BagIt Specification OLD

This page details the specification of DPN Content Packages.

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DPN requires packaging content for transport, but does not specify how each replicating node incorporates digital objects into their respective repositories.As an example SDR will serialize content in the /data directory in tar format, however, this may not be feasible for some repositories as the size of the serialized bag may be too large. We may want to consider the method of bag grouping, i.e. a bag directory that holds many serialized bags, all with the same profile and a sequence number associated with component bag.

DPN

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DPN Bag Structure

<DPN-Object-ID>/
         |   bagit.txt
         |   manifest-sha256.txt
         |   bag-info.txt
         |   tagmanifest-sha256.txt
         \--- data/
               |   [payload files]
         \--- dpn-tags/
               |   dpn-info.txt
         \--- [optional node tag directories]/
               |   [optional node tag files]

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• Required element from bagit spec. SHA256 is the DPN standard for fixity checksums (secure hash/message digest)
  • See http://csrc.nist.gov/groups/ST/toolkit/secure_hashing.html 
• Contains payload (content under /data) and associated checksums (secure hash(s))Note: As we update our fixity algorithms in the future we should keep old versions of this manifest file for auditing and historic purposes
  • There is some debate on the retention of legacy manifest-<alg>.txt files

bag-info.txt

• bagit spec section 2.2.2
• Using this to add additional information to help with succession
• Fields that may have been redundant with local dpn-info.txt fields are recommended to be kept in dpn-info.txt to avoid confusion
• DPN requires the presence of the following fields, although they may be empty.  Please note that the values of "null" and/or "nil" should not be used.  The colon (:) should still be present. Note, after further discussion, we determined that "empty" fields are consistent with both "human" readability and with current bagit community best practices. 08/20/2014 
  

   Source-Organization
   Organization-Address
   Contact-Name
   Contact-Phone
   Contact-Email
   Bagging-Date
   Bag-Size
   Bag-Group-Identifier
   Bag-Count

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Bag-Count

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• Other fields are optional for use by the First Ingest Node but are ignored by all common DPN processes.

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• bagit spec section 2.2.1
• Contains secure hash of tag files
• This will ensure the metadata we are storing with the bag is preserved
• As with manifest-sha256.txt we can keep old versions as we update our fixity algorithmsAll objects in the bag, including those in the optional tag directories must be represented in the tag manifest.

fetch.txt

• Not supported DPN as we do not support Holey-bags.

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• The naming convention of fields that hold DPN UUIDs have the suffix "Object-ID"
  
  • Alternative naming conventions to also be considered include: "OID", "DPN-ID", "DID", "Reference-ID", "Ref-ID", etc
• Every field must appear.  If a field does not have a value, it should still appear but be left blank.  
• All fields must have a value, except for:
  • PreviousFirst-Version-Object-ID
  • BrighteningInterpretive-Object-ID ("rights" and "brighteninginterpretive" only)*
  • Rights-Object-ID ("rights" and "brighteninginterpretive" only)*
    
  • * Currently, "data" bags also do not require this field.
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• Fields that could contain more than one value should be repeated for each value.  Do not separate with commas
  
  • Currently, the only fields that may be repeated are "BrighteningInterpretive-Object-ID" and "Rights-Object-ID".]
  • Example:

BrighteningInterpretive-Object-ID: UUID #1
BrighteningInterpretive-Object-ID: UUID #2
BrighteningInterpretive-Object-ID: UUID #3

optional node tag directory and files

• Following the bagit specification for optional tag directories and using the convention for DPN optional tags, first nodes MAY choose to include optional tags of their own which will be ignored by the DPN Federation as a whole
• As with the convention used with the DPN optional tags we recommend the directory naming convention of `<node name>-tags` and file naming convention of `<node name>-<filename>.txt` following the bagit specification
• First nodes that use this directory should strongly consider having a node-specific BagIt profile

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• If included, the files must be represented in tagmanifest-sha256.txt.
  
  

DPN Bag Transfer Protocol

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