2.6 Repeatable properties and classes

The standard allows for a degree of repeatability at both the class and property level: this should be understood as situations where a single class or property can be used, multiple instances of the class or property can also validly be used.

Over time different standards have handled repeatability by pipe-delimiting multiple values in a single field, versus nested or related tables or classes. Latimer Core aims to take a pragmatic approach, given the variety of possible relationships among classes.

Repeatable Properties

How repeatability is handled in a Latimer Core implementation depends largely on which data serialisation is used. Taking the period property of the ObjectGroup class as an example, the appropriate methods might be:

• an array, if using JSON or RDF

  "ltc:period": ["Neolithic Period", "McCarthy Era"]

• a normalised table, if using a relational database

  auto_id	ltc:period
  1	Neolithic Period
  2	McCarthy Era

• a repeated set of numbered columns for the same property, if using a spreadsheet or csv file (e.g. period.1, period.2)

  ltc:period.1	ltc:period.2
  Neolithic Period	McCarthy Era

• multiple pipe-delimited values, if using a flat text format

  ltc:period
  Neolithic Period | McCarthy Era

Repeatable Classes

How can classes be repeated?

As it stands, repeatable classes are repeatable in any context, i.e., regardless of the class to which they are attached. Some classes may seem to warrant different repeatability allowances in different situations. We leave the choice to the user.

Taking the Identifier class as an example, the appropriate methods for representing multiple identifiers for an ObjectGroup might be:

• an array of objects, if using JSON or RDF

  "Identifier": [
      {
          "ltc:identifierSource": "GrSciColl",
          "ltc:identifierValue": "urn:uuid:ea4f0640-ef20-40aa-b359-166f07c7492a",
          "ltc:identifierType": "UUID"
      },
      {
          "ltc:identifierSource": "GrBio",
          "ltc:identifierValue": "http://grbio.org/cool/zdsi-36ka",
          "ltc:identifierType": "LSID"
      }
  ]

• a normalised table, if using a relational database

  auto_id	ltc:identifierSource	ltc:identifierValue	ltc:identifierType
  1	GrSciColl	urn:uuid:ea4f0640-ef20-40aa-b359-166f07c7492a	UUID
  2	GrBio	http://grbio.org/cool/zdsi-36ka	LSID

• a repeated set of numbered columns for the same property, if using a spreadsheet or csv file

  ltc:identifierSource.1	ltc:identifierValue.1	ltc:identifierType.1	ltc:identifierSource.2	ltc:identifierValue.2	ltc:identifierType.2
  GrSciColl	urn:uuid:ea4f0640-ef20-40aa-b359-166f07c7492a	UUID	GrBio	http://grbio.org/cool/zdsi-36ka	LSID

• multiple pipe-delimited values, if using a flat text format

  • In Latimer Core, it is not recommended to repeat properties within repeatable classes. For example, if an identifierSource corresponded to two ltc:identifierValue values, repeat each identifier’s source, value, and type in parallel:

    ltc:identifierSource	ltc:identifierValue	ltc:identifierType
    GrSciColl | GrBio	urn:uuid:ea4f0640-ef20-40aa-b359-166f07c7492a | http://grbio.org/cool/zdsi-36ka	UUID | LSID

  • Do not nest comma-delimited values within pipe-delimited values:

    ltc:identifierSource	ltc:identifierValue	ltc:identifierType
    Ouch | Yikes	urn:uuid:ea4f0640-ef20-40aa-b359-166f07c7492a | http://grbio.org/cool/zdsi-36ka, http://grbio.org/cool/zdsi-36kb	UUID | LSID, LSID