Source: ISO 690, Clause 4.9
ISO 690, Clause 4.9 argues that unique international standard identifiers must be included in the bibliography. In practice, identifiers are included at the discretion of the bibliographer: they are routinely included in bibliographic databases, but seldom in references within documents.
The namespace of an identifier is indicated through its type attribute. The scope of an identifier is introduced to disambiguate the identifier referent, when it is not obvious. So it is introduced where an identifier identifies only a component of the item (e.g. a document included in the item), or a superset of the item (e.g. a series). It can also be used if the identifier identifies a specific instantiation of the document as an entity; in terms of the Functional Requirements for Bibliographic Records, for example, an identifier may identify a work, an expression of the work (e.g. an edition), a manifestation of the work (e.g. a format), or an item of the manifestation (e.g. a single physical copy).
Neither the type nor the scope of the identifier have an associated controlled vocabulary, and one is unlikely to be derived. Identifier type should follow established practice in the domain; most well-known identifiers have a widely used short name or abbreviation.
Invalid or cancelled identifiers should be so identified through the identifier scope: the cancellation of the identifier does not impact its namespace, but its connnection to a referent.
Standards body identifiers for standards (ISO 690, Clause 5.9) may be modelled as series numbers or as identifiers (Series). We recommend that the canonical identifier issued for a standard by a standards body be encoded as an identifier; other identifiers assigned to the same document may be better identified with a series title, as a named and numbered grouping of documents.
Identifiers can be expressed as HTTP URIs may be so expressed, without changing the identifier type. A DOI for example may be expressed as either the DOI proper, or as a doi.org URI.
International Journal of Islamic Thought. e-ISSN 2289-6023. ISSN 2232-1314.
<bibitem type="journal"> <title>International Journal of Islamic Thought</title> <docidentifier scope="digital" type="e-ISSSN">2289-6023</docidentifier> <docidentifier scope="print" type="ISSSN">2232-1314</docidentifier> </bibitem>
Ahmed al-Kindi & Anke Iman Bouzenita. 2018. The notion of Sunna: An eclectic reading in the Ibadhi legacy. International Journal of Islamic Thought 14:1-21. https://doi.org/10.24035/ijit.14.2018.001.
<bibitem type="article"> <title>International Journal of Islamic Thought</title> <docidentifier scope="journal" type="doi">10.24035/ijit</docidentifier> <docidentifier scope="article" type="doi">https://doi.org/10.24035/ijit.14.2018.001</docidentifier> </bibitem>