Mailing List Digest


  1. Reagan mentioning types of collections: Digital Collection, Data series, Sensor-based data series, Data set: discrete set, Data stream
  2. PIDs are not substrate
  3. need ontology/concepts/mereology
  4. PID != collection/resource
  5. PIDs important for RDA
  6. identifiers are usually digital identifiers in RDA context
  7. identifiers are bitstrings that can uniquely identify a resource
  8. identifiers are a property of the resource
  9. in RDA identifiers might be related to registries and repositories


  1. Collection: PID referencing a digital object containing a list of PIDs referencing objects and pointers to metadata
  2. Collection defined by explicit enumeration or by implicit rules
  3. Collections can be recursive
  4. Collection is finite if the recursively contained PIDs/IDs are finite
  5. Finite Collections solve issues in generative sets
  6. Rules:
  7. sub-collections (filtered)
  8. power collections
  9. flattened collections
  10. sub-trees in recursive collections [my addition: paths in RC]
  11. power collection of all previous versions
  12. Need solid formal foundation for provability
  13. alternatively no proof and use other mechanisms to guarantee consistency
  14. No decision on whether to use PID, ID or both
  15. currently no predicate other than partOf
  16. suggestion to type the partOf relation in collection metadata
  17. 2 collections are not the same if elements same, but relation-type different


  1. Unordered sets can be a benefit over lists computationally (Distributed HashMaps, NoSQL)


  1. Link to HTRC collection framework


  1. Collection != PID: PID points to an object that is the collection
  2. Recursive collections are limited by their hierarchical (DAG) topology: <list of examples>
  3. Let’s not use abstractions that lose semantics
  4. Identifier != Locator


  1. DC Collections definition: just aggregation of items, richer def. would limit applications
  2. Collection!=PID
  3. Choice of identifier type not trivial


  1. PID != Collection => referer != referent
  2. are collections blank nodes? precision imprecise!
  3. set::scalar <=> collection::vector
  4. gatheredInto describes process, ignoring possible actors (river/beach examples)
  5. role of a collection affects modelling needs
  6. use of metadata vs inspection of content - to identify a collection
  7. Identifiers are like labels, names except they’re digital
  8. "Identifier != Locator" is not as clear, identifiers are used to locate
  9. uniqueness and persistence of identifiers are contigent properties, contingent metaproperties of resources


  1. need licensing, policy metadata
  2. and access control