6. Structural Connections

6.1 Class Ranges and Relationships

The range of a LtC class defines the classes to which it can validly be attached. This is intended to provide guidelines for reasonable interconnections between classes that are useful when describing a given aspect of a collection. For example, the TemporalCoverage class can be validly attached to the CollectionStatusHistory, Event, or PersonRole classes in order to document the time spans for those classes.

Class Name	Range (i.e., other classes to which the class in the first column can be attached)
Address	OrganisationalUnit, Person, PersonRole, StorageLocation
ChronometricAge	ObjectGroup
CollectionStatusHistory	ObjectGroup
ContactDetail	OrganisationalUnit, Person, PersonRole
EcologicalContext	Event, ObjectGroup
Event	Event, ObjectGroup
GeographicContext	Event, ObjectGroup
GeologicalContext	ObjectGroup
Identifier	Address, ChronometricAge, CollectionStatusHistory, ContactDetail, EcologicalContext, Event, GeographicContext, GeologicalContext, LatimerCoreScheme, MeasurementOrFact, ObjectClassification, ObjectGroup, OrganisationalUnit, Person, PersonRole, RecordLevel, Reference, ResourceRelationship, Role, SchemeMeasurementOrFact, SchemeTerm, StorageLocation, Taxon
LatimerCoreScheme
MeasurementOrFact	ChronometricAge, CollectionStatusHistory, EcologicalContext, Event, GeographicContext, GeologicalContext, ObjectClassification, ObjectGroup, OrganisationalUnit, Person, PersonRole, StorageLocation, Taxon, TemporalCoverage
ObjectClassification	ObjectClassification, ObjectGroup
ObjectGroup	LatimerCoreScheme, RecordLevel
OrganisationalUnit	ObjectGroup, OrganisationalUnit
Person	PersonRole
PersonRole	Event, ObjectGroup, OrganisationalUnit, RecordLevel
RecordLevel
Reference	ChronometricAge, CollectionStatusHistory, EcologicalContext, Event, GeographicContext, GeologicalContext, Identifier, LatimerCoreScheme, MeasurementOrFact, ObjectClassification, ObjectGroup, OrganisationalUnit, Person, PersonRole, RecordLevel, ResourceRelationship, SchemeMeasurementOrFact, SchemeTerm, StorageLocation, Taxon, TemporalCoverage
ResourceRelationship	ObjectGroup, RecordLevel
Role	PersonRole
SchemeMeasurementOrFact	LatimerCoreScheme
SchemeTerm	LatimerCoreScheme
StorageLocation	ObjectGroup, StorageLocation
Taxon	ObjectGroup
TemporalCoverage	CollectionStatusHistory, Event, PersonRole

Table 9: Ranges for each Latimer Core class

Conversely, the class-level properties define which other classes can be attached to a given LtC class:

Class Name	Class-level Properties
Address	Identifier
ChronometricAge	Identifier, MeasurementOrFact, Reference
CollectionStatusHistory	Identifier, MeasurementOrFact, Reference, TemporalCoverage
ContactDetail	Identifier
EcologicalContext	Identifier, MeasurementOrFact, Reference
Event	EcologicalContext, GeographicContext, Identifier, MeasurementOrFact, Event, PersonRole, Reference, TemporalCoverage
GeographicContext	Identifier, MeasurementOrFact, Reference
GeologicalContext	Identifier, MeasurementOrFact, Reference
Identifier	Reference
LatimerCoreScheme	Identifier, ObjectGroup, Reference, SchemeMeasurementOrFact, SchemeTerm
MeasurementOrFact	Identifier, Reference
ObjectClassification	Identifier, MeasurementOrFact, ObjectClassification, Reference
ObjectGroup	ChronometricAge, CollectionStatusHistory, EcologicalContext, Event, GeographicContext, GeologicalContext, Identifier, MeasurementOrFact, ObjectClassification, OrganisationalUnit, PersonRole, Reference, ResourceRelationship, StorageLocation, Taxon
OrganisationalUnit	Address, ContactDetail, Identifier, MeasurementOrFact, OrganisationalUnit, PersonRole, Reference
Person	Address, ContactDetail, Identifier, MeasurementOrFact, Reference
PersonRole	Address, ContactDetail, Identifier, MeasurementOrFact, Person, Reference, Role, TemporalCoverage
RecordLevel	Identifier, ObjectGroup, PersonRole, Reference, ResourceRelationship
Reference	Identifier
ResourceRelationship	Identifier, Reference
Role	Identifier
SchemeMeasurementOrFact	Identifier, Reference
SchemeTerm	Identifier, Reference
StorageLocation	Address, Identifier, MeasurementOrFact, StorageLocation, Reference
Taxon	Identifier, MeasurementOrFact, Reference
TemporalCoverage	MeasurementOrFact, Reference

Table 10: Class-level properties for each Latimer Core class

6.2 Repeatability

The design decisions for the structure of LtC give rise to the general principle that, with one exception, only classes within the standard can be repeated, not individual properties within classes. For example, if a work phone contact point has two phone numbers, then the ltc:ContactDetail class is repeated for this contact point, resulting in two full sets of phone contact details. Repeating only the ltc:ContactDetail.contactDetailValue property, or changing its stored information from a single string to an array containing several strings, is not allowed. Such an approach would run counter to the spirit of the standard's design, and break its overall structure. In consequence, the contact point, e.g. a ltc:ObjectGroup or ltc:PersonRole that has the two phone contact options will have a "hasContactDetail" term, which represents and collects links to, i.e. stands in for the ltc:ContactDetail class, with a value that is an array storing the two sets of ltc:ContactDetail information as sub-arrays.

One important exception however, exists in the form of the standard's core ltc:ObjectGroup class that rests at the center of the standard's data model. In this class, all properties have as values arrays with zero to many entries. Thus, for an ltc:ObjectGroup that digitally represents a fish collection with objects preserved in alcohol or formaldehyde, ltc:ObjectGroup.preservationMethod validly can be represented as an array of [alcohol, formaldehyde].

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

Repeatable Properties

How repeatability is handled in an LtC implementation depends largely on which data serialisation format 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 LtC, 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