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Comments on "Dublin Core to PROV Mapping" - part 2 of 2

From: Thomas Baker <tom@tombaker.org>
Date: Sat, 30 Mar 2013 14:07:02 -0400
To: public-prov-comments@w3.org
Cc: Provenance Task Group <dc-provenance@jiscmail.ac.uk>
Message-ID: <20130330180702.GA38521@julius>
Daniel, Kai, other contributors,

Here is the second part of my comments on [1].  These comments
address issues in the Introduction re: Dublin Core and "DC Terms".

Tom

[1] http://www.w3.org/TR/2013/WD-prov-dc-20130312/ 

======================================================================
4. Issues in the Introduction re: Dublin Core and "DC Terms"

--  Characterizing the difference between Dublin Core and PROV-O.

    A number of interesting points are made in the text about the difference
    between DC and PROV, but they are scattered around the text.  For example:

    -- "A substantial number of terms in the Dublin Core vocabulary provide
       information about the provenance of the resource. Translating these terms
       to PROV makes the contained provenance information explicit within a
       provenance chain." [from the Abstract]

   -- "If an action is involved... then it is relevant for its provenance."

   -- "While Dublin Core includes provenance information, its focus lies on the
      broader description of resources. PROV models a provenance chain, but it
      provides almost no information about the involved resources themselves."
      [from the Conclusion]

   It would be nice to pull these insights together, for the benefit of the
   readier, in the Introduction.  I suggest a way to do this below.

-- Use of "DC Terms"

   The Introduction currently says:
        The Dublin Core Metadata Initiative (DCMI) [DCMI] provides a core metadata
        vocabulary (commonly referred to as Dublin Core) for simple and generic
        resource descriptions. The original element set (DC elements) was created
        in 1995 and contains 15 broadly-defined elements still in use. The core
        elements have no range specification, and arbitrary values can be used as
        objects. The core elements have been expanded beyond the original fifteen.
        Existing elements have been refined and new elements have been added. This
        expanded vocabulary is referred to as "DCMI Terms" (DC terms) and currently
        consists of 55 properties [DCTERMS].

        The use of DC terms is preferred and the DC elements have been
        depecreated. Both sets have different namespaces. The original element
        set is typically referred with the dc prefix, while dct (or dcterms) is
        used as prefix for the DC Terms.

        This document defines a mapping between the DC Terms and the PROV
        Ontology (PROV-O) [PROV-O], which defines an OWL2 Ontology encoding the
        PROV Data Model [PROV-DM]. 

    The situation is admittedly confusing -- a product of historical choices
    made more than a decade ago -- but basically:

    --  "DCMI Metadata Terms" is the name of a specification [1], periodically updated,
        that includes terms identified using using several namespace URIs, among which
        the ones of interest to us are: 
        
        -- http://purl.org/dc/elements/1.1/: the original namespace URI, with the 
           fifteen properties of "the Dublin Core," which were coined
           before the RDFS notions of domain and range had even been
           standardized, and which thus have no domains or ranges.  While the
           use of properties in the /terms/ vocabulary (below) is "gently
           promoted" by DCMI in the believe that terms with domains and ranges
           are more precise, in a helpful way, than terms which can take either
           an entity or a literal as object, there are people in the Dublin
           Core community who believe that "rangeless" (aka "free-range")
           properties are underspecified in a _helpful_ way.  These properties
           are still very widely used, and DCMI has carefully avoided saying
           they are "deprecated".  Indeed, they are no longer even referred to as 
           "legacy" properties.

        -- http://purl.org/dc/terms/: the namespace URI coined after we realized
           it was a bad idea to put version numbering into a namespace URI.  In 
           order to assign domains and ranges to the fifteen properties of "the Dublin 
           Core," we re-coined equivalents of the fifteen properties in the /terms/
           vocabulary and assigned domains and ranges to those.

    Without going into a long explanation in the prov-dc document, I suggest
    saying, simply:

        The Dublin Core Metadata Initiative (DCMI) [DCMI] provides a core
        metadata vocabulary (commonly referred to as Dublin Core) for simple
        and generic resource descriptions.[DCTERMS] The original Dublin Core Metadata
        Element Set was created in 1995 and contains fifteen broadly defined
        properties that are still in use.  Properties identified using the
        original namespace URI http://purl.org/dc/elements/1.1/ have no
        specified ranges, meaning that arbitrary values can be used as
        objects.  In order to assign ranges, DCMI replicated the fifteen
        properties using the namespace URI http://purl.org/dc/terms/.  Additional
        properties and classes beyond the original fifteen were coined using
        this namespace URI.  In this document, properties and classes using the
        /terms/ namespace URI are referred to, simply, as DC Terms.
        
        This document defines a mapping between the DC Terms and the PROV
        Ontology (PROV-O) [PROV-O], which defines an OWL2 Ontology encoding the
        PROV Data Model [PROV-DM].  [@@@ - see below] This mapping has been
        designed for several purposes:

        1.  Bridge the gap between the DC and PROV communities, in order to
            provide valuable insights into the different characteristics of both
            data models.
        2.  Help developers to derive PROV data from the large amount of Dublin
            Core data available on the web, improving interoperability between DC
            and PROV applications.
        3.  Facilitate PROV adoption. Simple Dublin Core statements can be used
            as a starting point for more complex PROV data generation.

-- To follow up on my point above re: the differences between DC and PROV, 
   I suggest adding a paragraph at the point marked "[@@@]" above that says,
   roughly:
        
        The PROV vocabulary and data model are focused on expressing actions
        and resource states in a provenance chain rather than on describing
        resources in a general sense.  The Dublin Core vocabulary is focused on
        describing resources in a general sense, but a substantial number of
        terms in the vocabulary provide information related to the provenance
        of the resource. Mapping statements using Dublin Core into statements
        using PROV makes the contained provenance information explicit.

[1] http://dublincore.org/documents/dcmi-terms/

-- 
Tom Baker <tom@tombaker.org>
Received on Saturday, 30 March 2013 18:07:36 UTC

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