Referring to segments of a file - Recommendation

This recommendation is for referring to segments within a File using the following selectors appended to URIs.  SoaF Use Cases outline most significant formats for Samvera/Fedora applications. Use cases are listed below with reference to the fragment selector spec, when available, and examples. Open Annotation Fragment Selectors covers many but not all formats to refer to segments.
 

Time-based media [spatial or temporal]

• Temporal - Avalon Media System uses W3C Media Fragments for referring to segments of a file (example with Track 2 being called up using https://pawpaw.dlib.indiana.edu/media_objects/avalon:9651/section/avalon:9652?t=131.0,332.0). 
• Spatial - For visual time-based media only. Refer to a static portion of the screen view of a video file during playback.

XML-encoded texts

• Refer to a specific region of an XML document:
  • Restrict a search to all instances of an element
  • Retrieve content from a specific instance of an element for display
• Refer a PCDM page object to a region within an XML-encoded text and vice versa

PDF

• Refer to a specific page of a PDF
• Within a single page of PDF file:
  • Refer to a predefined anchor point ("destination" in Adobe parlance) in a PDF
    •  Requires that destination is already defined in the PDF
  • Refer to an arbitrary region of a PDF

Image

SVG

• Draw vector as mask on region of other image file to show portion
  •  4 points (rectangular)
  •  more or less than 4 points (non-rectangular)

<svg height="100" width="100">
  <circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" /> 
</svg>

Other image formats

• Refer to size of image to show
• Refer to region of image to show portion