The BagIt Team of the Beyond the Repository project is recommending changes to the BagIt Profiles specification.

This PR updates the BagIt Profiles specification to:

• Add a new optional description property for free-form textual description related to Bag-Info tags.
• Add support for specifying lists of allowed payload and tag manifest types/algorithms via the Manifests-Allowed and Tag-Manifests-Allowed properties, respectively.
• Bump version number.

These changes are non-breaking for v1.2.0, thus packages built to that specification would not require changes (aside from BagIt-Profile-Identifier tag in bag-info.txt).

• The description property of the Bag-Info object is optional.
• The Manifests-Allowed and Tag-Manifests-Allowed lists are optional and reasonable behaviors are defined for the default values.

Description Property

The description property enables the conveyance of any information that might be helpful to either the producer or the consumer of a bag to understand how to provide or interpret the information associated with a particular tag. There is no restriction on the length of description, so it may be less than ideal to use as a tooltip for its associated tag.

Manifests-Allowed and Tag-Manifests-Allowed Properties

With Manifests-Required and Tag-Manifests-Required, the current BagIt Profiles specification (v1.2.0) supports the enumeration of any algorithms for which a corresponding payload or tag manifest, respectively, MUST be present in a bag. If these lists are specified, though, all listed algorithms must be represented.

We needed an additional mechanism through which to designate the set of algorithms supported (rather than required) by the consumer of a bag, so that producers are able create bags appropriately. Manifests-Allowed and Tag-Manifests-Allowed fulfill this need. If unspecified, these properties impose no constraints on the algorithms available to a producer. If Manifests-Required is specified, then if Manifests-Allowed is specified, it must include at least those algorithms listed in Manifests-Required. The same relationship applies for Tag-Manifests-Required/Tag-Manifests-Allowed.