Introduction

The purpose of the BagIt Profiles Specification is to allow creators and consumers of Bags to agree on optional components of the Bags they are exchanging. Details of the Profile are instantiated in a JSON ([[RFC8259]]) file that both the producing and consuming applications interpret using the conventions described below. The Profile file sits at an HTTP URI (e.g., `http://example.com/bagitprofiles/profile-bar-v0.1.json`), and can therefore be read by any number of applications creating or consuming Bags:

                                  BagIt Profile JSON file

                                        /       \
                                       v         v
                        Bag creating app 1  -->  Bag consuming app
                        Bag creating app 2
        

This proposed Specification builds on the sample Profile included in the Library of Congress Bagger tool. However, that Profile was local to LC and not intended to be implemented widely. The proposed Specification is intended to be an optional extension to the cannonical BagIt spec, and in no way modifies that specification. Like [[RFC8493]], this specification is agnostic to the payload stored in a Bag's data directory.

Use cases for BagIt Profiles include distributed mass production of Bags, repository or application-specific content ingestion via Bags (e.g. SWORD, Archivematica), and Preservation-as-a-Service.

Workflow

The intended workflow for using a BagIt Profile is:

1. The creator of the Bags ensures that Bags it produces meet all of the constraints expressed in the agreed-upon and published BagIt Profile file. The creator declares the `BagIt-Profile-Identifier` in the `bag-info.txt` file of the Bags.
2. The consumer of the Bags identifies the Profile(s) from the `BagIt-Profile-Identifier` field in their `bag-info.txt`. The consumer then retrieves the Profile file from its URI and validates incoming Bags against it; specifically, it must complete the Bag if `fetch.txt` is present, validate the complete Bag against the Profile, and then validate the Bag against the cannonical BagIt spec.

Each of these steps may be performed by a separate tool or microservice; in fact, implementers may integrate validation functionality in tools that perform other Bag-processing functions. For example, the completion of a holey Bag might be performed by a more general Bag-processing tool and need not be delegated to a separate validation tool.

Some Profile constraints are fatal: for example, failure to validate 'Accept-Serialization' or 'Accept-BagIt-Version' implies that the rest of the bag is unverifiable and processing should stop. Therefore, the task that checks these two constraints should be performed as early as possible in the workflow. Processing may continue after non-fatal errors in order to generate a comprehensive error report.

Implementation Details

Bags complying to a BagIt Profile MUST contain the tag `BagIt-Profile-Identifier` in their `bag-info.txt`, which value is the URI of the JSON file containing the BagIt Profile it conforms to. This tag MAY be repeated if the Bag conforms to multiple BagIt Profiles. The URI that identifies the BagIt Profile SHOULD be versioned, e.g. `http://example.com/bagitprofiles/profile-bar-v0.1.json`.

Resolving the URI with `Accept: application/json` SHOULD provide a BagIt Profile as JSON according to this specification.

1. `BagIt-Profile-Info`:

   A list of tags that describes the Profile itself. The following tags are required in this section: `Source-Organization`, `External-Description`, `Version`, and `BagIt-Profile-Identifier`. Starting with version [`v1.2.0`], `BagIt-Profile-Version` is also required.

   The `Source-Organization` and `External-Description` tags are taken from the reserved tags defined in [[!RFC8493]] section 2.2.2.

   The value of `Version` contains the version of the Profile; the value of `BagIt-Profile-Identifier` is the URI where the Profile file is available, and will have the same value as the `BagIt-Profile-Identifier` tag in `bag-info.txt`.

   The value of `BagIt-Profile-Version` contains the version of this specification that the BagIt Profile conforms to, e.g. `"1.3.0"`. Since the tag was introduced after version `1.1.0`, any profile not explicitly defining `BagIt-Profile-Version` should be treated as conforming to version `1.1.0` of this specification.

   Inclusion of `Contact-Name`, `Contact-Phone` and `Contact-Email` is OPTIONAL as defined in [[RFC8493]] section 2.2.2, but is encouraged.

2. `Bag-Info`:

   Specifies which tags are required, etc. in `bag-info.txt`. Each tag definition takes four optional parameters:

   1. `required` is true or false (default `false`) and indicates whether or not this tag is required.
   2. `values` is a list of acceptable values. If empty or missing, any value is accepted.
   3. `repeatable` is `true` or `false` (default `true`) to indicate whether or not this tag can be repeated in `bag-info.txt`.
   4. `description` is a string providing notes or description related to this tag.

   Implementers may define in the `Bag-Info` section of their BagIt Profile whatever tags their application requires, i.e., tags defined here are not limited to the 'reserved metadata element names' identified in [[!RFC8493]] section 2.2.2.

   The tag `BagIt-Profile-Identifier` is always required, but SHOULD NOT be listed under `Bag-Info` in the Profile.

3. `Manifests-Required`: LIST

   Each manifest type in LIST is required. The list contains the type of manifest (not the complete filename), e.g. `["sha1", "md5"]`.

4. `Manifests-Allowed`: LIST

   If specified, only the manifest types in LIST are permitted. The list contains the type of manifest (not the complete filename), e.g. `["sha1", "md5"]`.

   When specified along with `Manifests-Required`, `Manifests-Allowed` must include at least all of the manifest types listed in `Manifests-Required`.

   If not specified, all manifest types are permitted.

5. `Allow-Fetch.txt`: `true`|`false`

   A fetch.txt file is allowed within the bag. Default: `true`

6. `Fetch.txt-Required`: `true`|`false`

   Only specify when `Allow-Fetch.txt` is `true`. Default is `false`.

7. `Data-Empty`: `true`|`false`

   If `true` then the `/data` directory must contain either no files or a single zero byte length file. If `false`, no constraints are placed on the `/data` directory. Default is `false`.

8. `Serialization`: `forbidden`|`required`|`optional`

   Allow, forbid or require serialization of Bags. Default is `optional`.

9. `Accept-Serialization`: LIST

   A list of MIME types acceptable as serialized formats. E.g. "application/zip". If serialization has a value of required or optional, at least one value is needed. If serialization is forbidden, this has no meaning.

10. `Accept-BagIt-Version`: LIST

    A list of BagIt version numbers that will be accepted, e.g. "1.0". At least one version is required.

11. `Tag-Manifests-Required`: LIST

    Each tag manifest type in LIST is required. The list contains the type of manifest (not the complete filename), e.g. `["sha1", "md5"]`.

12. `Tag-Manifests-Allowed`: LIST

    If specified, only the tag manifest types in LIST are permitted. The list contains the type of manifest (not the complete filename), e.g. `["sha1", "md5"]`.

    When specified along with `Tag-Manifests-Required`, `Tag-Manifests-Allowed` must include at least all of the tag manifest types listed in `Tag-Manifests-Required`.

    If not specified, all tag manifest types are permitted.

13. `Tag-Files-Required`: LIST

    A list of a tag files that MUST be included in a conformant Bag. Entries are full path names relative to the Bag base directory. As per [[RFC8493]] section 2.2.4, these tag files need not be listed in tag manifiest files. `Tag-Files-Required` SHOULD NOT include `bag-info.txt` (which is always required), nor any required manifest files, which instead are required by `Manifests-Required` and `Tag-Manifests-Required`.

    Every file in `Tag-Files-Required` MUST also be covered by the path patterns in `Tag-Files-Allowed`.

14. `Tag-Files-Allowed`: LIST

    A list of tag files that MAY be included in a conformant Bag. Entries are either full path names relative to the bag base directory or path name patterns in which asterisks can represent zero or more characters (c.f. glob(7)).

    Conformants bags MUST NOT contain any payload that does not match the specified `Tag-Files-Allowed`. If `Tag-Files-Allowed` is not provided, its value is assumed to be `['*']`, i.e. all tag files are allowed.

    As per [[RFC8493]] section 2, these tag files need not be listed in tag manifest files. `Tag-Files-Required` SHOULD NOT include `bag-info.txt` (which is always required), nor any required manifest files, which instead are required by `Manifests-Required` and `Tag-Manifests-Required`.

    At least all the tag files listed in `Tag-Files-Required` MUST be in included in `Tag-Files-Allowed`.

15. `Payload-Files-Required`: LIST

    A list of a payload files and/or directories that MUST be included in a conformant Bag. Entries are full path names relative to the Bag base directory, e.g. `data/LICENSE.txt` or `data/src/`. Paths requiring directory existence MUST end with `/`, indicating that in conformant Bags, the directory MUST be present with at least one file or subdirectory (which may have a placeholder file to indicate an empty directory, see [[RFC8493]] section 2.1.3).

    Every file in `Payload-Files-Required` MUST also be covered by the path patterns in `Payload-Files-Allowed`.

16. `Payload-Files-Allowed`: LIST

    A list of payload files or directories that MAY be included in a conformant Bag. Each entry MUST be either a full path name relative to the bag base directory, or a path name pattern in which asterisks can represent zero or more characters (c.f. [glob(7)](http://man7.org/linux/man-pages/man7/glob.7.html)). Paths requiring permitted directories MUST end with `/*` (not `/`).
    

    Conformants bags MUST NOT contain any payload that does not match the specified `Payload-Files-Allowed`. If `Payload-Files-Allowed` is not provided, its value is assumed to be ['*'], i.e. all payload files and directories are allowed.

    At least all the payload paths listed in `Payload-Files-Required` MUST be covered by the list of path patterns in `Payload-Files-Allowed`.

Examples

          {
             "BagIt-Profile-Info":{
                "BagIt-Profile-Identifier":"http://www.library.yale.edu/mssa/bagitprofiles/disk_images.json",
                "BagIt-Profile-Version": "1.1.0",
                "Source-Organization":"Yale University",
                "Contact-Name":"Mark Matienzo",
                "External-Description":"BagIt Profile for packaging disk images",
                "Version":"0.3"
             },
             "Bag-Info":{
                "Bagging-Date":{
                   "required":true
                },
                "Source-Organization":{
                   "required":true,
                   "values":[
                      "Simon Fraser University",
                      "York University"
                   ]
                },
                "Contact-Phone":{
                   "required":true
                }
             },
             "Manifests-Required":[
                "md5"
             ],
             "Allow-Fetch.txt":false,
             "Serialization":"required",
             "Accept-Serialization":[
                "application/zip",
                "application/tar"
             ],
             "Accept-BagIt-Version":[
                "0.96",
                "0.97"
             ]
          }
        

          {
             "BagIt-Profile-Info":{
                "BagIt-Profile-Identifier":"http://canadiana.org/standards/bagit/tdr_ingest.json",
                "BagIt-Profile-Version": "1.2.0",
                "Source-Organization":"Candiana.org",
                "Contact-Name":"William Wueppelmann",
                "Contact-Email":"tdr@canadiana.com",
                "External-Description":"BagIt Profile for ingesting content into the C.O. TDR loading dock.",
                "Version":"1.2"
             },
             "Bag-Info":{
                "Source-Organization":{
                   "required":true,
                   "values":[
                      "Simon Fraser University",
                      "York University"
                   ]
                },
                "Organization-Address":{
                   "required":true,
                   "values":[
                      "8888 University Drive Burnaby, B.C. V5A 1S6 Canada",
                      "4700 Keele Street Toronto, Ontario M3J 1P3 Canada"
                   ]
                },
                "Contact-Name":{
                   "required":true,
                   "values":[
                      "Mark Jordan",
                      "Nick Ruest"
                   ]
                },
                "Contact-Phone":{
                   "required":false
                },
                "Contact-Email":{
                   "required":true
                },
                "External-Description":{
                   "required":true
                },
                "External-Identifier":{
                   "required":false
                },
                "Bag-Size":{
                   "required":true
                },
                "Bag-Group-Identifier":{
                   "required":false
                },
                "Bag-Count":{
                   "required":true
                },
                "Internal-Sender-Identifier":{
                   "required":false
                },
                "Internal-Sender-Description":{
                   "required":false
                },
                "Bagging-Date":{
                   "required":true
                },
                "Payload-Oxum":{
                   "required":true
                }
             },
             "Manifests-Required":[
                "md5"
             ],
             "Allow-Fetch.txt":false,
             "Serialization":"optional",
             "Accept-Serialization":[
                "application/zip"
             ],
             "Tag-Manifests-Required":[
               "md5"
             ],
             "Tag-Files-Required":[
                "DPN/dpnFirstNode.txt",
                "DPN/dpnRegistry"
             ],
             "Accept-BagIt-Version":[
                "0.96"
             ]
          }