Dataset granularities: Abstract vs. Versioned vs. Layer

When csv2rdf4lod converts tabular data to RDF, it also asserts metadata about the RDF using the conversion vocabulary. One type of metadata that it asserts is void:Dataset details, which lets us group collections of triples in a hierarchical fashion. csv2rdf4lod groups triples into three specific types of void:Dataset:

• conversion:AbstractDataset (subclass of void:Dataset)
  • conversion:VersionedDataset (subclass of void:Dataset that is a void:subset of conversion:AbstractDataset)
    • conversion:LayerDataset (subclass of void:Dataset that is a void:subset of conversion:VersionsedDataset)

So, the "largest" void:Dataset in the list above is conversion:AbstractDataset, and the "smallest" is conversion:LayerDataset.

As described in the naming phase, three provenance-related aspects are used to organize any third party data that csv2rdf4lod retrieves, converts, and republishes. This allows us to clearly distinguish where our data came from, and which version we actually got. Each aspect is given a short, URI-friendly identifier string:

• source identifier - indicates the person/agent/organization that provided the data. For example, "epa-gov" provides a variety of datasets.
• dataset identifier - indicates the logical group of data. For example, the EPA distinguishes between the datasets "photochemical-assessment-monitoring-stations-pams" and "historical-radnet-air-quality-data".
• version identifier - indicates the version of a particular dataset. For example, you could have retrieved version "r23" (a designation from EPA themselves) three years ago, or I could have retrieved version "2013-Mar-14" today (because the EPA didn't provide a version designation for what they provided). For naming conventions, see naming.

Given the base URI of our Linked Data site (say, http://lod.mine.org), we can create URIs for different groups of triples (void:Datasets):

• http://lod.mine.org/source/epa-gov/dataset/photochemical-assessment-monitoring-stations-pams
  • http://lod.mine.org/source/epa-gov/dataset/photochemical-assessment-monitoring-stations-pams/version/2011-Jan-11
  • http://lod.mine.org/source/epa-gov/dataset/photochemical-assessment-monitoring-stations-pams/version/2013-Mar-14
• http://lod.mine.org/source/epa-gov/dataset/historical-radnet-air-quality-data
  • http://lod.mine.org/source/epa-gov/dataset/historical-radnet-air-quality-data/version/r23
  • http://lod.mine.org/source/epa-gov/dataset/historical-radnet-air-quality-data/version/2013-Mar-14