Overview

The need for identifiers in metadata records was first recognized in the DIF Standard and FGDC Remote Sensing Extensions. These standards introduced identifiers for the metadata records. In ISO 19115 this role is addressed by the fileIdentifier, a character string included in the MD_ or MI_Metadata object. This character string has been replaced with an MD_Identifier in  19115-1.

Including fileIdentifiers in the ISO metadata records gives metadata creators a mechanism for uniquely identifying them. This is becoming more important as metadata records evolve from single files into collections of related objects that can be harvested into repositories like geo.data.gov along multiple paths. There is no reliable way to identify duplicate records without a unique identifier in the actual record.

If the metadata records belongs to a parent metadata collection the parentIdentifier field can be use to identify the collection.

Identifiers are also used to reference resources associated with the data set or service described by the metadata. For example platforms, instruments, software, documentation, reports, partners and products can all be unambiguously referenced in and described with the MD_Identifier object.