4. PIDINST metadata schema
The metadata that is to be registered with an instrument PID needs to contain enough information to unambiguously identify the instrument across networks and infrastructures. It should also allow linking related resources to the instrument, thus providing a means to aggregate information about the instrument. The PIDINST working group defined a schema of metadata that can be registered alongside instrument PIDs at PID providers to help meet these criteria. Version 1.0 has been endorsed as an RDA recommendation.[1]
Currently, two variants of the metadata schema exist. The original PIDINST schema, based on the evaluation of use cases collected by the working group, is used for prototypical implementation of metadata properties in the ePIC infrastructure. A second variant provides a mapping between PIDINST metadata properties and DataCite Metadata Schema 4.3. In the following, we describe the properties in the original PIDINST schema and discuss their semantics:
- Identifier
The PID of the instrument. The subproperty identifierType contains the type of the PID, e.g. Handle or DOI in the case of an ePIC Handle or a DataCite DOI respectively.
- SchemaVersion
The version number of the PIDINST schema used to create a record.
- LandingPage
The URL of the landing page that the PID resolves to.
- Name
The name by which this instrument is known. It should preferably be meaningful and unique within the organization that manages it.
- Owner
The organization or individual that manages the instrument. This may or may not be the legal owner. It could also be an organization that hosts or operates the instrument, manages its deployment, or provides access to it. In case of doubt, it would be the instance that a potential user would reach out to in order to get access. There may be more then one owner registered in the metadata.
Owner is a complex property having at least the subproperty ownerName and optionally a contact address in ownerContact and a common identifier of the owner in ownerIdentifier and its type in ownerIdentifierType.
- Manufacturer
The organization or individual that built the instrument. In the case of an off the shelf product, this will probably be a commercial company that put the instrument on the market. In the case of an custom built instrument, the manufacturer may be the same as the owner. In the latter case, they would be registered as both, owner and manufacturer. In case of doubt, the manufacturer would be the instance that defined the technical specification of the instrument. Again, there may be more then one manufacturer registered in the metadata.
In the same way as Owner, Manufacturer is a complex property with subproperties manufacturerName, manufacturerIdentifier and manufacturerIdentifierType.
- Model
The name of the model or type of the instrument. In the case of an off the shelf product, this may be a brand name attributed by the manufacturer. In the case of a custom built instrument, it may not have a model name. Hence this property is not mandatory, but recommended if the value can be obtained. Model has optional subproperties modelIdentifier and modelIdentifierType to be used if an identifier for the model is known.
- Description
A textual description of the device and its capabilities. This is mostly targeted to a human reader and should provide a notion of what this instrument is and what it can do.
- InstrumentType
A classification of the type of the instrument. Hierarchical classification enables grouping of instrument records.
In the same way as Owner, Manufacturer and Model, InstrumentType is a complex property with subproperties instrumentTypeName, instrumentTypeIdentifier and instrumentTypeIdentifierType.
- MeasuredVariable
The variables or physical properties that the instrument measures or observes. Some communities have established terminologies to identify measured variables that are specific to their respective domain (see Using common terminologies). If such a standard is applicable, it should be used for for MeasuredVariable. Otherwise, a textual description may be used.
- Date
Relevant events pertaining to this instrument instance, such as when it has started and ended to be in operation. Each Date need to have a dateType subproperty to specify the nature of the event.
- RelatedIdentifier
This can be used to establish links to related resources, such as documents describing the instrument or external metadata records, possibly using other metadata standards to provide more details about the instrument.
Another application might be, if an instrument has been substantially modified, it would make sense to issue a new PID for the modified instrument with a new metadata record. In this case both PIDs should relate to each other to indicate that one is a new version of the other.
Furthermore, in the case of a complex instrument, it can make sense to issue PIDs for individual components, such as an individual detector in a larger experimental station. In this case, the relation between the complex instrument and its components should be established by creating links between the respective PIDs.
The links established using this property are particuarly useful as they allow the automatic aggregation of a rich set of information about the instrument. Each RelatedIdentifier needs to have subproperties relatedIdentifierType and relationType to specify the type of the related identifier and the type of the relation respectively.
- AlternateIdentifier
If the instrument instance is also registered elsewhere, aside from the persistent identifier, AlternateIdentifier is the place to store a reference to these register entries. Common use cases are the serial number attributed by the manufacturer or inventory number used by the owner. But also other instrument databases or access portals may hold an entry for the instrument that should be referenced from the PIDINST metadata.
The subproperty alternateIdentifierType needs to specify the kind of the alternate identifier. Standardized values should be used where applicable. For serial and inventory numbers, the suggested values are serialNumber and inventoryNumber respectively.