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The PAIS specifies a standard packaging mechanism for the implementation of PAIS SIPs. It is based on use of the XFDU packaging standard. When this is followed, and the semantics of PAIS section 5 are followed, the resulting implementation is said to be ‘XFDU PAIS SIP Conformant’. However, it is acceptable to use other packaging mechanisms. In this case the resulting SIP implementation can be said to be ‘Abstract PAIS SIP Conformant’ provided it also adheres to the semantics of PAIS section 5.
Relationship between SIP Model and Bag-info.txt
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Use of the BagIt specification does not necessarily result in an a SIP that conforms to the abstract SIP specification defined in PAIS. Further enhancements are required.
The following table illustrates the relationship between metadata elements specified in Section 2.2.2 of the BagIt File Packaging Format and the SIP Model attributes specified in Section 5.2.4 of PAIS. In some cases, the relationship is implicit
Bag-info.txt field | Description | PAIS SIP model attribute | Notes |
|---|---|---|---|
Source-Organization | Organization transferring the content. | Producer source ID | |
Organization-Address | Mailing address of the organization. | N/A | |
Contact-Name | Person at the source organization who is responsible for the content transfer. | N/A | |
Contact-Phone | International format telephone number of person or position responsible. | N/A | |
Contact-Email | Fully qualified email address of person or position responsible. | N/A | |
External-Description | A brief explanation of the contents and provenance. | N/A | This information maps to the "transfer object type description" attribute in a transfer object type descriptor |
Bagging-Date | Date (YYYY-MM-DD) that the content was prepared for transfer. This metadata element SHOULD NOT be repeated. | ||
External-Identifier | A sender-supplied identifier for the bag. | ||
Bag-Size | The size or approximate size of the bag being transferred, followed by an abbreviation such as MB (megabytes), GB (gigabytes), or TB (terabytes): for example, 42600 MB, 42.6 GB, or .043 TB. Compared to Payload-Oxum (described next), Bag-Size is intended for human consumption. This metadata element SHOULD NOT be repeated. | This information maps to the transfer object type size attribute in a transfer object type descriptor | |
Payload-Oxum | The "octetstream sum" of the payload, which is intended for the purpose of quickly detecting incomplete bags before performing checksum validation. This is strictly an optimization, and implementations MUST perform the standard checksum validation process before proclaiming a bag to be valid. This element MUST NOT be present more than once and, if present, MUST be in the form "_OctetCount_._StreamCount_", where _OctetCount_ is the total number of octets (8-bit bytes) across all payload file content and _StreamCount_ is the total number of payload files. This metadata element MUST NOT be repeated. | ||
Bag-Group-Identifier | A sender-supplied identifier for the set, if any, of bags to which it logically belongs. This identifier SHOULD be unique across the sender's content, and if it is recognizable as belonging to a globally unique scheme, the receiver SHOULD make an effort to honor the reference to it. This metadata element SHOULD NOT be repeated. | ||
Bag-Count | Two numbers separated by "of", in particular, "N of T", where T is the total number of bags in a group of bags and N is the ordinal number within the group. If T is not known, specify it as "?" (question mark): for example, 1 of 2, 4 of 4, 3 of ?, 89 of 145. This metadata element SHOULD NOT be repeated. If this metadata element is present, it is RECOMMENDED to also include the Bag-Group-Identifier element. | ||
Internal-Sender-Identifier | An alternate sender-specific identifier for the content and/or bag. | ||
Internal-Sender-Description | A sender-local explanation of the contents and provenance. |