File: Subtypes and Use Cases¶

For decades, libraries, archives, and museums have attempted to create a semantic registry for file formats to help institutions preserve and understand digital content. The first and most successful attempt at this historically has been PRONOM. In early 2011, PRONOM released its Linked Data Version, but it was shuttered several years later. Between 2005 and 2015, other efforts were made in this area in the Global Digital Format Registry and Unified Digital Format Registry. Unfortunately, both efforts collapsed and the work of both is no longer available online.

When PCDM started, there was an effort to try and bring UDFR ideas into PCDM via the File Formats Extension. While some context is now lost due to decision making in PCDM, leveraging classes defined here here affords us a straight forward solution for making interoperability with other formats such as IIIF Presentation easier.

In addition to the File Formats Extension, PCDM Use Extension defines classes that are not directly derived from the projects above but instead are common use cases in repositories.

This section defines some subclasses of pcdm:File that may be used in place of or addition to pcdm:File.

Philosophy¶

There are multiple ways to model files. For our purposes, we do not care about capturing every subclass that applies to a single file. Instead, we want to prescribe and select subclasses that apply to our use cases in as few conepts as possible. For this reason, we will attempt to apply only one subclass per File unless additional classes are needed to successully capture semantic meaning.

Canvases¶

A Canvas, as defined by IIIF presentation, acts as a central point for assembling the different content resources that make up the display of a work. In IIIF, files with a motivation="painting" are added to the canvas and displayed directly to users in a viewer, while other Files may be served by the viewer indirectly. In our repository, we need a way to differentiate between these types of files. This section describes the different file types that may be painted on a canvas.

Image¶

Important

Files that are conventionally thought of as images (e.g. TIFs, JPGs, JP2s, etc.) may be stored as a file of a work but not intended for display. For our purposes, these are not considered Images and are not modelled as below.

Any images that are painted on a Canvas should be an instance of pcdmff:Image. Images of pages of books may need to be a part of a pcdmworks:FileSet in order to be understood with OCR. Regardless an image that is painted on a canvas should look something like this and may have more or fewer triples depending on decisions made elsewhere in this document:

@prefix ex: <http://example.org/> .
@prefix fedora: <http://fedora.info/definitions/v4/repository#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix pcdm: <http://pcdm.org/models#> .
@prefix pcdmff: <http://pcdm.org/file-format-types#> .
@prefix pcdmuse: <http://pcdm.org/use#> .
@prefix nepomuk: <http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#> .
@prefix exif: <http://www.w3.org/2003/12/exif/ns#> .
@prefix ebucore: <http://www.ebu.ch/metadata/ontologies/ebucore/ebucore#> .
@prefix premis: <http://www.loc.gov/premis/rdf/v1#> .

ex:Image a pcdmff:Image;
    pcdm:fileOf ex:ImageWork ;
    fedora:hasBinary <https://path/to/preservation%20file.tif> .
    ebucore:width "2106"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:fileSize "17765536"^^<http://www.w3.org/2001/XMLSchema#string> ;
    premis:hasSize "17765536"^^<http://www.w3.org/2001/XMLSchema#long> ;
    exif:orientation "normal*"^^<http://www.w3.org/2001/XMLSchema#string> ;
    exif:colorSpace "RGB"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:hasMimeType "image/tiff"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:height "2808"^^<http://www.w3.org/2001/XMLSchema#string> ;
    nepomuk:hashValue "99d14ee8c28517e10c637e0e0a675b94"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:filename "preservation file.tif"^^<http://www.w3.org/2001/XMLSchema#string> ;
    exif:software "Adobe Photoshop CS2 Windows"^^<http://www.w3.org/2001/XMLSchema#string> .

Audio¶

Important

Files that are conventionally thought of as audio (e.g. WAVs, MP3s, etc.) may be stored as a file of a work but not intended for display on a Canvas. For our purposes, these are not considered Audios and are not modelled as below.

Any audio files that should be painted on a Canvas should be an instance of pcdmff:Audio. Audio files may be part of a pcdmworks:FileSet in order to be understood with a transcript fo the audio. Regardless any audio file that is painted on a canvas should look something like this and may have more or fewer triples depending on decisions made elsewhere in this document:

@prefix ex: <http://example.org/> .
@prefix fedora: <http://fedora.info/definitions/v4/repository#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix pcdm: <http://pcdm.org/models#> .
@prefix pcdmff: <http://pcdm.org/file-format-types#> .
@prefix nepomuk: <http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#> .
@prefix ebucore: <http://www.ebu.ch/metadata/ontologies/ebucore/ebucore#> .
@prefix premis: <http://www.loc.gov/premis/rdf/v1#> .

ex:Audio a pcdmff:Audio;
    pcdm:fileOf ex:OralHistory ;
    fedora:hasBinary <https://path/to/audio%20file.wav> .
    premis:hasSize "17765536"^^<http://www.w3.org/2001/XMLSchema#long> ;
    ebucore:hasMimeType "audio/wav"^^<http://www.w3.org/2001/XMLSchema#string> ;
    nepomuk:hashValue "99d14ee8c28517e10c637e0e0a675b94"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:filename "audio file.tif"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:duration "6542"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:hasLanguage "en" .

Video¶

Important

Files that are conventionally thought of as video (e.g. MP4s, MOVs, MKVs, etc.) may be stored as a file of a work but not intended for display on a Canvas. For our purposes, these are not considered Videos and are not modelled as below.

Any video files that should be painted on a Canvas should be an instance of pcdmff:Video. Video files may be part of a pcdmworks:FileSet in order to be understood with a closed captioning or subtitle file of the video. Regardless any video file that is painted on a canvas should look something like this and may have more or fewer triples depending on decisions made elsewhere in this document:

@prefix ex: <http://example.org/> .
@prefix fedora: <http://fedora.info/definitions/v4/repository#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix pcdm: <http://pcdm.org/models#> .
@prefix pcdmff: <http://pcdm.org/file-format-types#> .
@prefix nepomuk: <http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#> .
@prefix ebucore: <http://www.ebu.ch/metadata/ontologies/ebucore/ebucore#> .
@prefix premis: <http://www.loc.gov/premis/rdf/v1#> .

ex:Video a pcdmff:Video;
    pcdm:fileOf ex:OralHistory ;
    fedora:hasBinary <https://path/to/video%20file.mkv> .
    premis:hasSize "17765536"^^<http://www.w3.org/2001/XMLSchema#long> ;
    ebucore:hasMimeType "video/mkv"^^<http://www.w3.org/2001/XMLSchema#string> ;
    nepomuk:hashValue "99d14ee8c28517e10c637e0e0a675b94"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:filename "video file.tif"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:duration "4443"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:hasLanguage "es" .

Other Files¶

Not all files in our repository are intended to be served by a viewer by being painted on a canvas. This section covers any known or common use cases

Closed Captioning of Subtitle File¶

A video work may have many closed captioning or subtitle files. In a IIIF context, these target canvases directly (not files) so it’s important to not that this might be the case in our repository too.

OCR Text¶

Structured ALTO XML or HOCR¶

Dataset¶

Generic Files¶

Any file that is generic is important to a work, but only needs to be served indirectly. Generic files can be of any mime type but are intended to be downloaded from a viewer rather than served in another way. Those files should be modelled as follows:

@prefix ex: <http://example.org/> .
@prefix fedora: <http://fedora.info/definitions/v4/repository#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix pcdm: <http://pcdm.org/models#> .
@prefix nepomuk: <http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#> .
@prefix ebucore: <http://www.ebu.ch/metadata/ontologies/ebucore/ebucore#> .
@prefix premis: <http://www.loc.gov/premis/rdf/v1#> .

ex:GenericFile a pcdm:File;
    pcdm:fileOf ex:Work ;
    fedora:hasBinary <https://path/to/generic%20file.jpg> .
    premis:hasSize "17765536"^^<http://www.w3.org/2001/XMLSchema#long> ;
    ebucore:hasMimeType "image/jpeg"^^<http://www.w3.org/2001/XMLSchema#string> ;
    nepomuk:hashValue "99d14ee8c28517e10c637e0e0a675b94"^^<http://www.w3.org/2001/XMLSchema#string> ;
    ebucore:filename "generic file.tif"^^<http://www.w3.org/2001/XMLSchema#string> .