Works Extension

The Hydra implementation of PCDM added a few subclasses of PCDM Object to refine the relationships between a work and its constituent parts:

• Work: A work or intellectual entity, such as a book, film, dissertation, etc. Works have member FileSets representing their physical structure (e.g., pages in a book), and related TopRanges representing their logical structure or structures (e.g., sections and chapters in a book).

• FileSet: A group of related Files, typically a single master File and its derivatives.

• TopRange: A logical ordering of the component parts of a Work, corresponding to a IIIF Range with the "top" viewing hint. Has member Ranges that represent the logical structure, such as chapters within a book, scenes in a film, etc.

• Range: A section of a Work, corresponding to a IIIF Range. Has member FileSets representing the physical parts of the Work are part of the section (e.g., which pages are in a chapter).

Physical and Logical Structure

FileSets are used to encode the physical structure of the resource. They correspond to pages in a book, tracks in an audio recording, or original born-digital files. There is typically a single, flat list of FileSets in a Work.

TopRange and Range are used to encode one or more logical structures that can be applied to the resource. These might follow the hierarchy expressed in a table of contents. Or they might reflect other groupings of content that can be presented to a user. Each TopRange represents a single structure, and has a hierarchy of member Ranges to represent the individual sections, chapters, etc.