datapack, a container for packages of data and associated metadata
Source:R/datapack-package.r
datapack.RdThe datapack R package provides an abstraction for collating
heterogeneous collections of data objects and metadata into a bundle that can
be transported and loaded into a single composite file. The methods in
this package provide a convenient way
to load data from common repositories such as DataONE into the R environment,
and to document, serialize, and save data from R to data repositories worldwide.
A data package is represented as an instance of the S4 class DataPackage, which
consists of one or more instances of the S4 DataObject class, which in turn contains
an instance of the S4 SystemMetadata class. The SystemMetadata
class provides critical metadata about a data object that is needed to transport
it to an external repository, including the identifier for the object, its
format, its checksum and size, and information about which repositories the
data is associated with. DataPackages can be loaded from and saved to the
DataONE federated network of repositories using the dataone package, but they
can also be used as standalone transport containers for other systems.
A DataPackage includes a manifest based on the OAI-ORE specification for describing aggregations of files as a ResourceMap. Resource maps are RDF documents that conform to the Open Archives Initiative Object Reuse and Exchange (OAI-ORE) specification. Resource maps are generated by data providers to define data packages, and have a namespace of http://www.openarchives.org/ore/terms/.
A DataPackage is serialized as a zip file following the BagIt RFC specification, which provides a consistent mechanism for a serialized representation of a group of opaque objects in a predictable structure. BagIt includes a specification for including metadata about each of the objects, the bag itself, and fixity attributes so that any BagIt implementation can validate the components contained within a package. When expanded, a BagIt zipfile will expand to a common directory structure with a predictable set of metadata that describes the structure and content of the bag. Conformance with the BagIt specification is handled by the DataPackage class.
Classes
DataPackage-class: A class representing a data package, which can contain data objectsDataObject-class: DataObject wraps raw data with system-level metadataSystemMetadata-class{SystemMetadata}: A DataONE SystemMetadata object containing basic identification, ownership, access policy, replication policy, and related metadata.ResourceMap-class{ResourceMap}: ResourceMap provides methods to create, serialize and deserialize an OAI ORE resource map.