I've been looking into this and the formal specification of an ORCID identifier is the full resolvable URL:
"The ORCID iD is an https URI with a 16-digit number that is compatible with the ISO Standard (ISO 27729), also known as the International Standard Name Identifier (ISNI), e.g. https://orcid.org/0000-0001-2345-6789"
The ORCID case is actually quite interesting as not using a URL actually seems to break some DataCite commons referencing and you loose some nice functionality
Similarly both Crossref and DataCite recommend in their best practices that DOI's be displayed as full URL's as doi.org URL's are PURLS and therefore can act as identifiers.
https://support.datacite.org/docs/datacite-doi-display-guidelines
I've been looking into this and the formal specification of an ORCID identifier is the full resolvable URL:
"The ORCID iD is an https URI with a 16-digit number that is compatible with the ISO Standard (ISO 27729), also known as the International Standard Name Identifier (ISNI), e.g. https://orcid.org/0000-0001-2345-6789"
The ORCID case is actually quite interesting as not using a URL actually seems to break some DataCite commons referencing and you loose some nice functionality
Similarly both Crossref and DataCite recommend in their best practices that DOI's be displayed as full URL's as doi.org URL's are PURLS and therefore can act as identifiers.
https://support.datacite.org/docs/datacite-doi-display-guidelines