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The business of unique identification

What need is there for unique identifiers?

Put in relatively non-technical language, there is an increasing concern in information science in general to uniquely identify different things, organisations or people that could otherwise be confused, whether on the Internet or in the physical world. In technical terms, these are all referred to as resources (even if people might find it vaguely demeaning in normal language to be considered as such). This need, whether real or perceived in any particular context, has grown as the complexity of information available on the Web has grown almost exponentially, increasing the potential for confusing similar resources.

Why aren't names good enough?

1. People

It is not necessarily enough to have a name, since even a relatively unusual combination of names might easily not be entirely unique from a worldwide or even universal perspective: at the basic level, John Steven Smith might be unique in a place called Barton but even if you cross-reference these references, two people with the same name could easily be confused, for example if there are several possible places called Barton.

My own name, Talat Zafar Chaudhri, might appear to be more unique until you realise that these are all fairly common names in the Indian subcontinent and thus in the Indo-Pakistani diaspora, so it is reasonably possible or even fairly likely that another named individual exists with this particular choice of spelling (of which others may exist). I am also Talat Chaudhri, T. Chaudhri, T Chaudhri, T.Z. Chaudhri, TZ Chaudhri and similar variations (with or without spaces and punctuation) that might make it harder to decide which individuals to reconcile as a single individual, especially by machine processing. At least I do not vary the spelling of my surname, but some people may, especially in cases such as my own where other transliterations could be possible: for example, my father previously used the spelling Chaudhry and many others such as Chaudry, Chowdhary  and Chowdhuri are equally possible. I understand when companies misspell it, but a computer might not be sure if these were definitely the same person, even if it went to the lengths of calculating a probability for this.

Moreover, people change personal titles (e.g. I have been both a Mr and a Dr and I am occasionally still referred to as the former by companies that do not allow for the latter option); they have multiple, changing work roles and work places, and may be known in multiple contexts, e.g. work, social, voluntary roles and similar. At work, one may have additional roles in various professional bodies, so it may not be apparent who is who. Two people might have the same name in a large professional group, e.g. physicists, and may even produce outputs related to the same subject. Who owns which ones? This is a particular issue for electronically available outputs on the Internet, e.g. publications, educational resources, audio, visual or audiovisual resources and so on.

2. Organisations

The same issue arises for organisations. Can we be sure that a Board of Licencing Control is unique? No. Perhaps it is merely another spelling for the Board of Licensing Control but using a different spelling? What if one, but not all, of these were re-named as Burundian Licencing Control? What if the Board of Licencing Control merged with the Department for Regulatory Affairs under either of these names, a combination, or an entirely new name, yet continued their association with the assets of the originals. De-mergers are likewise possible, and may present issues of uncertain ownership of resources.

Perhaps there are organisations with this name in several countries but serving utterly different purposes, and perhaps one is merely one possible translation of a term into English but used natively in another language. Historical names have been used in multiple contexts that may still be valid, e.g. the Irish Volunteers, and these might need to be kept clearly separate from each other. Conversely, there are also organisations that have multiple names or forms of names, whether in one language or in multiple languages or during their history, e.g. Óglaigh na hÉireann is Irish for both the terrorist Irish Republican Army (IRA) and most of its subsequent splinter groups but is also, however, an acceptable name, for historical reasons, for the Defence Forces of the Republic of Ireland, and previously just the Irish Army (an tArm) that now forms a part of it. These are clearly not the same and must be distinguished. It must be also noted that typographical constraints and character encodings will lead to yet more duplicate forms.

Isn't this bigger than the question of unique identification?

Yes, the need for complex metadata to express these things can go far beyond merely identifying resources in a unique manner. However, before one can even start thinking about complex descriptive and relational metadata, one first has to be clear which resource is mentioned: hence the first step must be unique identification of what it is we are talking about. Only once we have done that can we feel reasonably confident about talking about how resources relate to one another and how they may have changed over time.

Overall, there is an ever increasing need to make clear what is meant, as more and more things and agents have on-line identities that need to be distinguished, whether this is as an owner of resources or as a referrant within a resource, e.g. the subject of the resource in a particular context, and even of the role played and the relationship to other resources or agents, perhaps in a specific time period. Information models can quickly become extremely complex, and this is certainly true where identity is concerned.

What is an identifier?

In concept, an identifier is similar in its basic concept to a name. At its most basic, an identifier in the context of an information system is a token (usually a number or a string of characters) used to refer to an entity (anything which can be referred to). Identifiers are fundamental to most, if not all, information systems. As the global network of information systems evolves, identifiers take on a greater significance. And as the Web becomes more 'machine readable', it becomes vital for all organisations who publish Internet resources to adopt well-managed strategies for creating, maintaining and consistently using identifiers to refer to those assets it cares about.

What are unique identifiers?

The simple answer is that this is the only way to avoid misidentification confidently, and therefore prevent any errors about ownership or rights over resources that might arise, as well as making sure that large bodies of resources contain reliable information generally.

The fundamental question is whether the identifier or token that has been chosen is unique and how best to ensure this. Some identifiers are so complex that mathematical probability makes them effectively unique in the universe, notably UUIDs. In essence, a UUID is no more than a complex numerical token: it is only additional complexity (and thus uniqueness) that it offers compared to, for example, a running number.  Others like names can only be distinguished unambiguously by making a series of statements about which names are considered equivalent, which contexts (e.g. a person's work or town) are valid, and so on, where a number of relationships have to be attached to a particular identifier and checked in order to reach an acceptable level of uniqueness and to eliminate any mistaken connections with resources that might be similar in name or perhaps also in other respects by chance.

The problem with UUIDs is that, while the chances of them failing to be unique are, to all practical purposes, non-existent, it is not very clear from a UUID alone what the nature of that resource is. It may be machine-readable but it says nothing about who generated that identifier and when, or which other identifiers might exist for the same resource in different systems that also generated an identifier for the same resource. Consequently, the need to associate other metadata with any complex number or other similar token remains (including but not limited to UUIDs). Simply, no single token can be sufficient for any complex purpose and, at the very least, an electronic or physical resource must be referenced for the token to have any useful meaning at all.

This is effectively that a URL is: another type of token. While I will not go into the whole discussion about URLs and URNs as sub-types of URIs, it is worth noting that, in many quarters, the term URL is no longer preferred despite it being the most commonly used in practice. In strict terms, there is a clear difference: while a URI is usually resolvable to an electronic resource, which may be either a description of a physical or electronic resource or may be an electronic resource itself, there is technically no requirement that a URI should be resolvable, i.e. that all it needs to be is a token that doesn't necessarily have to represent an address that actually delivers a resource. However, it is usual to use the HTTP scheme, which is designed for delivering such a resource, so it would be somewhat eccentric and misleading if one were deliberately to choose an ostensibly resolvable syntax that does not in fact resolve. In effect, virtually all such URIs are also URLs (unless a resource has become unavailable and link rot has set in), since the latter must locate the resource or representation of it: this is inherently useful. Any URI that resolves, i.e. URL, will be effectively unique within the standard Domain Name System (DNS). As a result, there is no absolute need for UUIDs in many contexts, since a sufficiently unique and practical token already exists in the URI. Any unique but arbitrary token serves the core purpose here.

Aren't identifiers really just names?

Yes and no. Names are intrinsically arbitrary too when they are first given. However, they are identifiable on a number of levels from a human perspective. In addition to a combination of names belonging to one or more particular linguistic and/or ethnic origins and usually identifying gender, they quickly become associated with a particular person, so their use in uniquely identifying that person within a given context become central to maintaining the person's reputation in whatever they do. This is, for example, particularly important to academics in Higher Education. In modern times, this name resolution needs to be done globally wherever the Internet is the context, whereas previously it would have been possible to use fewer additional pieces of information in more restricted contexts (e.g. a village, a country etc), depending on the purpose. These different contexts still co-exist but it is now necessary to provide as many as possible, since one cannot control or predict why the information is being requested in each instance on a global system such as the Internet.

How does this affect Higher and Further Education?

Increasing numbers of professionals and the bodies that they work for and represent need to describe their resources on the Internet, whether those are in themselves electronic resources, whether they are descriptions of electronic or physical resources (metadata), or whether they are other representations of physical resources, perhaps in addition to themselves being electronic resources (e.g. photographs). This is a particularly pressing issue in Higher Education and, to an increasing extent, in Further Education. Academic outputs may include publications, educational resources, visual, audio and audiovisual resources and so on. Perhaps the best known is the issue of scholarly publications, partly through the rise of the Open Access movement to make such resources freely available.

There are already a range of identifiers for academics and related professional university staff. One of the problems is that these are created for specific purposes that only cover whichever subset of staff is relevant to those purposes. For example, HESA keeps records that contain a HESA number for academic staff, which means that at least those who have published academic outputs will have such a number. Another number called the HUSID number is maintained for students, since tracking academic careers from student to staff is one important concern for HESA. Many academics in relevant fields may have ISNI numbers, which are used widely in the media content industries. Many academics will have one or more professional staff pages, including within repositories and Current Research Information Systems (CRIS), each with a URI, not to mention OpenIDs and URIs associated with Web services which they use professionally and/or privately, e.g. LinkedIn,, Facebook, Twitter and so on.

Here are some examples belonging to Brian Kelly of UKOLN:

The problem is that the coverage of these numbers is not universal within the HE sector, and there is no single recognised authority or other agreement to prevent and resolve conflicts where information is not consistent between two or more information sources.

At present, the JISC are trying to solve this through the Unique Identifiers Task and Finish Group, which also includes representatives of HESA, HEFCE, the various Research Councils in the UK and UKOLN. The preferred solution is currently the ORCID academic identifier, which is being developed internationally with publishers, with a great deal of input from the United States in particular.

In order to succeed, any such identifier will need international penetration of the higher education sector, since academics will not use it unless it delivers the sorts of interoperability benefits that make their work easier and become integrated into the recognised systems required of them by funders and publishers in the course of their work. Since students and academics change roles and institutions, this needs to be recognised and outputs properly allocated to institutions and departments, which may themselves change identities, merge and de-merge over time.

While institutions will need to reduce the workload on academics by bulk loading information about staff, since the main incentive to use the system is that every academic has a record, there is also an issue about control. Should academics have the ability to alter their records at will? Are assertions automatically trusted or does a particular record for an academic's time at an institution need to be verified by that trusted body? Who should maintain a list of trusted bodies who can back up assertions? How will this effort be funded sustainably? It becomes clear that some of these points are central structural concerns whereas others may cover only fringe issues such as avoiding deliberate falsification, which may be rare.

Proprietary academic identifiers

There are also a number of proprietary identifiers associated with different commercial services related to electronic publishing and related academic service industries. Thomson Reuters and Elsevier provide identities for individuals and organisations as part of their bibliographic and academic services; similarly, search services such as Google Scholar (see the study in this blog post) and Microsoft Academic Search have also started to offer identifiers (see this blog post). There may be privacy issues, for example in Google and Microsoft publicly surfacing information about researchers without explicit consent: while this information might have been suitable for the limited purpose of publication, academics may not have intended for it to be synthesised into a single, public description of their personal details available to all.

Some of these services introduce new problems, since their primary purpose is commercial and it is often less of a priority to deal with the internal issues facing academic institutions unless that impacts significantly on the ability to make commercial profit. These may be resolved over time or be reintroduced as services change and compete: the academic has little or no control over the effects of commercial decisions upon their work. For example, Microsoft Academic Search often misrepresents outputs as belonging to similarly named individuals (thus is currently failing at unique identification) and, by default, requires the manual input of researchers to edit out errors and take a proactive approach towards managing the information about themselves. This brings the overall quality of data into question: for large-scale statistical purposes, this could be tolerable, depending on the degree of error; however, for academic citations and reporting purposes such as the Research Excellence Framework (REF), it would not be acceptable to use this data without further refinement, which would most likely remain a long, manual process.

Software and services

Any software application layer, whether operated by commercial companies, higher educational institutions, funders or governmental bodies, needs to be maintained. If information is harvested or processed automatically, it needs to be clear who corrects information where errors are found and what the resources are for academics to contact individuals with the time and effort available to improve the data as part of their work. In the case of commercial organisations, this is usually unclear and may change. There is no guarantee that the commercial reason for providing services will continue over time, unlike in most cases in the public sector within Higher Education. Coverage of such commercial services is often geared towards institutions rather than individuals: for example, Google Scholar requires registration using a valid university email address that it recognises, which would exclude private scholars and perhaps some retired staff who produce research.

The Web of Things

It has already been mentioned that electronic descriptions or other representations of physical objects may be found on the internet, including written descriptions, pictures, geographical locations, dimensions and so on. It is even possible to describe physical objects that were extant but are now historical, or which have moved or whose location is now unknown, referencing comparable objects and linking these descriptions with other resources that are related. In each case, the nature of the relationship, relevant agents who may have been responsible for it, and when it was valid can be described in metadata.

This opens the way for the Web of Things, a term used to describe that part of the Semantic Web that covers physical resources as opposed to, or as well as, purely electronic ones. Some authorities use the term to mean physical objects with miniaturised electronic devices to enable them to be located, whereas others merely mean any physical object that is described in a record on the Web. It may be argued that all electronic resources have relationships to physical ones, even if that is only with regard to authorship and subject. The Resource Description Framework (RDF) provides a means to describe these relationships and transmit information about them in ways readable to humans and machines. Although these are usually expressed as triples, where two things are described with a relationship between them, metadata structures such as the Common European Research Information Framework (CERIF) can add link tables that give far more detailed information about the relationships themselves. All of this can be made available as Linked Data and surfaced in many software applications on the Web.

The Semantic Web is often seen as a utopian view of a future where no electronic resources will be published without complex information being provided or automatically generated about its origins. The reality is that manual entry of information is generally very limited unless it serves the purposes of the person entering it, and this cannot be relied upon as an approach to ensuring large-scale, consistent metadata on a sufficient scale for the Semantic Web to work. Technology has in some cases improved to the extent that geographical and technical information is now automatically produced, for example in digital cameras and in mobile phones able to record GPS coordinates.

However, the effort and cost required to catalogue the entire physical world and the extent to which this is even possible is highly doubtful. Where the Semantic Web could be useful is within particular large bodies of data, for example experimental scientific data, publications and so on. In the case of the Web of Things, this could include art collections, photography, archaelogical information, the locations of public institutions and many more. For all of these purposes, it will be necessary to provide unique identifiers for increasingly large numbers of resources, including things and agents, in order to provide complex metadata about them.

Education in the wider world

It has perhaps not been sufficiently investigated how unique identifiers for researchers and other staff in Higher Education will fit into the wider question of unique identification on the Web. Relevant purposes might be:

(1) commercial, for example the identification of companies and individuals owning the rights to photos, music, video or publications, particularly legacy resources of ongoing commercial value in terms of royalties and performance licencing.

(2) governmental, for example biometric information about people, used in border controls, crime prevention and citizenship contexts; or about public or private organisations such as charities, political groups of interest to law enforcement etc. Information about individuals, in particular, may be subject to privacy laws, which will vary between jurisdications.

It is clear that there are interfaces between the various agents and outputs of academic institutions and many other purposes, notably those commercial and governmental activities already described. For example, a foreign student or member of staff seeking a work permit will require institutions and governmental bodies to use personal and citizenship information co-operatively, which will be linked to their academic identity in the course of their work at the institution. Some of this information will be private and some public, so there is an issue about who can see which parts of a particular corpus of Linked Data, requiring authentication protocols and systems.

The extent to which consistency of approach between HE institutions and other sectors and contexts can ever be ensured is moot, since there is of course no single international authority and because any single metadata solution that tried to cover so many diverse purposes would be fatally unwieldy. How different, flexible approaches can be understood by machine processing is perhaps the technological key to how well the Semantic Web will answer these questions in future, both within Higher Education and beyond.


Hi Talat Thanks for this

Hi Talat

Thanks for this introduction to the issues of unique identifiers. In this context, I'd like to mention the JISC-funded Names Project in this context. As I'm sure you're aware, this project has been working for the past few years in building a pilot identifier service for UK researchers and research institutions. Building on the work of the JISC Merit project, supplemented with information from UK institutions, we've uniquely identified over 47,000 UK researchers.

Names has built disambiguating algorithms which enable us to match other data sets against our existing information to determine whether an individual already has a Names identifier or can be assigned a new one. APIs give open access to the data we hold in a variety of formats.


Dr. Radut | blog_post_tf