Doms Data Model

In the following these shorthands will refer to the following namespaces

• rdf - http://www.w3.org/1999/02/22-rdf-syntax-ns#

• rdfs - http://www.w3.org/2000/01/rdf-schema#

• owl - http://www.w3.org/2002/07/owl#

• fedora-model - info:fedora/fedora-system:def/model#

• doms-relations - http://doms.statsbiblioteket.dk/relations/default/0/1/#

• doms - Standard prefix for PIDs. It is not a namespace

A definition: A datamodel describes the content of a collection. A content model describes the content of a data object. So, a data model is a set of content models, that together describe the collection.

ImageLink(http://merkur/viewvc/trunk/docs/datamodel/fig/DOMSBaseCollection.png?root=doms&view=co,alt=DOMS base collection,width=256)

The DOMS datamodel describes how the Type system underlying DOMS is realised in Fedora 3. The figure above will serve as a guide through the following sections.

DOMS Content Models in general

Fedora provides a repository for digital objects. All objects in the repository can, in principle, be unique, but Fedora provides a way of specifying that an object has a given type. Unfortunately, the type-definitions in Fedora, called Content Models, are rather simplistic by default. We use them as the basis of our type system, with certain enhancements.

For our purposes, there are two kinds of digital objects in Fedora

• Data objects
• Content Model objects

The Content Model object, as used in DOMS, describes the compulsary and legal content of an object of this type. It contains the information nessesary to verify if the given object is indeed of this type. For more detail on this, see FedoraOntology and FedoraTypeChecking

A data object can specify the Content Model describing its contents, via a fedora-model:hasModel relation, and in DOMS we require it to be present. A data object will be said to "subcribe" to a Content Model. Content Model inheritance, as specified in FedoraOntology, will be used.

The special Content Model object "doms:ContentModel_DOMS" is the root object. All Content Models must have an "doms-relations:extendsModel" relation to this object, possibly through a number of other Content Models. The complete description of a data object is defined as the set of the descriptions in the Content Model specified with "fedora-model:hasModel" and all Content Models that can be reached from this, by following "doms-relations:extendsModel" relations.

A Content Model can "extend" more than one other Content Model. There is no overriding of Content Models, a subscribing object must be valid in regards to all the Content Models in the inheritance tree.

Schema Objects

XXXXX Many of the schemas used in DOMS need to be referenced many times. To avoid duplication, we have made objects containing only schemas, subcribing to the Content Model "doms:ContentModel_Schema". The describing datastream in a schemabinding might contain the schema directly, or it might contain the URL to the datastream that does. Either way, it should be invisible to programs accessing the datastream through the API.

DOMS Base Collection

Doms come shipped with a base collection of objects, representing the base types. The objects in the base collection will be detailed in the following.

Shorthand:

• myObject.myDatastream means the Datastream myDatastream in the Object myObject.
• $variable introduces a variable.

ContentModel_DOMS

ContentModel_DOMS is the root of the content model inheritance tree. All content models derive from this model. As all data objects in DOMS must have a content model, all data objects must adhere to the restrictions defined in this content model.

The ONTOLOGY datastream.

<rdf:RDF
        xmlns:owl="http://www.w3.org/2002/07/owl#"
        xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
        xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
        xml:base="http://doms.statsbiblioteket.dk/relations/default/0/1/#">

    <owl:Class rdf:about="info:fedora/doms:ContentModel_DOMS">

        <rdfs:subClassOf>
            <owl:Restriction>
                <owl:onProperty rdf:resource="isPartOfCollection"/>
                <owl:minCardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">1</owl:minCardinality>
            </owl:Restriction>
        </rdfs:subClassOf>

        <rdfs:subClassOf>
            <owl:Restriction>
                <owl:onProperty rdf:resource="isPartOfCollection"/>
                <owl:allValuesFrom rdf:resource="info:fedora/doms:ContentModel_Collection"/>
            </owl:Restriction>
        </rdfs:subClassOf>

        <rdfs:subClassOf>
            <owl:Restriction>
                <owl:onProperty rdf:resource="hasLicense"/>
                <owl:cardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">1</owl:cardinality>
            </owl:Restriction>
        </rdfs:subClassOf>

        <rdfs:subClassOf>
            <owl:Restriction>
                <owl:onProperty rdf:resource="hasLicense"/>
                <owl:allValuesFrom rdf:resource="info:fedora/doms:ContentModel_License"/>
            </owl:Restriction>
        </rdfs:subClassOf>

    </owl:Class>

    <owl:ObjectProperty rdf:about="isPartOfCollection"/>

    <owl:ObjectProperty rdf:about="hasLicense"/>
</rdf:RDF>

In humanreadable format it says that all subscribing objects must have a "doms-relations:hasLicense" relation to a object of "doms:ContentModel_License". Also, it must have one or more "doms-relations:isPartOfCollection" relations to objects of "doms:ContentModel_Collection".

DS-COMPOSITE datastream.

<dsCompositeModel
        xmlns="info:fedora/fedora-system:def/dsCompositeModel#"
        xmlns:schema="http://doms.statsbiblioteket.dk/types/dscompositeschema/0/1/#">

    <dsTypeModel ID="DC">
        <form MIME="text/xml"/>
        <extensions name="DOMS">
            <schema:schema type="xsd" datastream="DC_SCHEMA"/>
        </extensions>
    </dsTypeModel>
    <dsTypeModel ID="POLICY">
        <form MIME="text/xml"/>
    </dsTypeModel>
    <dsTypeModel ID="STATE">
        <form MIME="text/xml"/>
        <extensions name="DOMS">
            <schema:schema type="xsd" datastream="STATE_SCHEMA"/>
        </extensions>
    </dsTypeModel>
    <dsTypeModel ID="RELS-EXT"/>
</dsCompositeModel>

In human readable format, this say that all subscribing objects must have the following datastreams "DC", "POLICY", "STATE" and "RELS-EXT". The "DC" stream must conform to the schema defined in the datastream "DC_SCHEMA", in "doms:ContentModel_DOMS". The "STATE" stream must conform to the schema in datastream "STATE_SCHEMA" in "doms:ContentModel_DOMS". To understand the use of the "STATE" datastream, see the FedoraTransactionsReplacement. The use of the "POLICY" stream is defined in FedoraLicensePolicies. The "AUDIT" stream is detailed in DomsAuditTrail.

The DC_SCHEMA stream is just an xml schema and looks like this -- REF to OAIDUBLINCORE XXXXX Regard this

ContentModel_File

Extends ContentModel_DOMS

In DOMS, we have found it beneficial to separate the abstract concept of "Image" or "Audio" from the concrete implementations such as "jpeg" and "mp3". The metadata about the image will be relevant no matter the manifestation of the image, and as such should not reside along with the technical metadata about the manifestation. To support this separation, we have introduced the concept of File objects.

A File object is an object, that contain a link to the file (in Bitstorage), and the technical metadata about this file. Only File objects are allowed to reference a file in Bitstorage. File objects must all have a Content Model that extends ContentModel_File.

The following variables are used:

• $OrigFile: An object with the Content Model that derives from ContentModel_File;

Requirements for objects described by ContentModel_File

• ObjectProperties

  • External Properties

    • http://doms.statsbiblioteket.dk/extproperties/#pronomID : The pronom ID of the file

• Datastreams
  • RELS-EXT

    • (optional) doms:hasOriginal -> $OrigFile

  • CHARACTERISATION: The output of the characterisation tools. Schema attachment:Characterisation.xsd
  • CONTENTS: Datastream containing the file

    • ContentLocation URL = The file in Bitstorage

  • ORIGIN: Metadata about the creation of the file, in the Premis [http://www.loc.gov/standards/premis/v1/Event-v1-1.xsd schema]

The characterisation datastream could look like this.

<?xml version="1.0" encoding="UTF-8"?>
<char:characterisation xsi:schemaLocation="http://doms.statsbiblioteket.dk/types/characterisation/0/1/# http://developer.statsbiblioteket.dk/DOMS/types/characterisation/0/1/characterisation/characterisation-0-1.xsd"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:char="http://developer.statsbiblioteket.dk/DOMS/types/characterisation/0/1/#"
  xmlns:jhove="">
  <char:characterisationRun>
    <char:tool>JHove</char:tool>
    <char:output>
      <jhove:...>
      </jhove:...>
    </char:output>
  </char:characterisationRun>
</char:characterisation>

ContentModel_ImagePreservationFile

Extends ContentModel_File

Requirements for objects described by ContentModel_ImagePreservationFile

• Datastreams
  • PRONOMID: must be "fmt/10" (tiff version 6)

ContentModel_TextPreservationFile

Extends ContentModel_File

Requirements for objects described by ContentModel_TextPreservationFile

• Datastreams
  • PRONOMID: must be "x-fmt/16" (Utf8) or "fmt/95" (pdf-a)

ContentModel_VideoPreservationFile

Extends ContentModel_File

Requirements for objects described by ContentModel_VideoPreservationFile

• Datastreams
  • PRONOMID: must be "x-fmt/385" (mpeg1) or "x-fmt/386" (mpeg2)

ContentModel_AudioPreservationFile

Extends ContentModel_File

Requirements for objects described by ContentModel_AudioPreservationFile

• Datastreams
  • PRONOMID: must be "fmt/2" (Bwf version 1) or "fmt/6" (wav)

ContentModel_Image

Extends ContentModel_DOMS

The following variables are used:

• $ImageFile: An object with the Content Model ContentModel_ImagePreservationFile

Requirements for objects described by ContentModel_Image

• Datastreams
  • RELS-EXT

    • doms:hasPreservationFile -> $ImageFile

ContentModel_Audio

Extends ContentModel_DOMS

The following variables are used:

• $AudioFile: An object with the Content Model ContentModel_AudioPreservationFile;

Requirements for objects described by ContentModel_Audio

• Datastreams
  • RELS-EXT:

    • doms:hasPreservationFile -> $AudioFile

ContentModel_Video

Extends ContentModel_DOMS

The following variables are used:

• $VideoFile: An object with the Content Model ContentModel_VideoPreservationFile;

Requirements for objects described by ContentModel_Video

• Datastreams
  • RELS-EXT:

    • doms:hasPreservationFile -> $VideoFile

ContentModel_Text

Extends ContentModel_DOMS

The following variables are used:

• $TextFile: An object with the Content Model ContentModel_TextPreservationFile;

Requirements for objects described by ContentModel_Text

• Datastreams
  • RELS-EXT:

    • doms:hasPreservationFile -> $TextFile

ContentModel_License

Extends ContentModel_DOMS

Requirements for objects described by ContentModel_License

• Datastreams

  • LICENCE: XACML describing the license. [http://www.oasis-open.org/committees/download.php/915/cs-xacml-schema-policy-01.xsd Schema]

  • DC: The DC datastream (probably the description field) is used to describe the human readable version of the license

ContentModel_Schema

Extends ContentModel_DOMS

Requirements for objects described by ContentModel_Schema

• Datastreams
  • SCHEMA: The xsd schema inlined.

ContentModel_Collection

Extends ContentModel_DOMS

Requirements for objects described by ContentModel_Collection: None

Technical Metadata

A file object should contain technical metadata. In this context it refers

• A datastream with the output of the characterisation tools used on this file upon ingest, called CHARACTERISATION
• A datastream with the metadata about the origins of the file, called Origin

In addition, it must have a relation "hasOriginal" if it was migrated from another file that exists in DOMS.