Overview of content related to 'uri' http://www.ariadne.ac.uk/taxonomy/term/2643/all?article-type=&term=&organisation=&project=&author=kerry%20blinco&issue= RSS feed with Ariadne content related to specified tag en Abstract Modelling of Digital Identifiers http://www.ariadne.ac.uk/issue62/nicholas-et-al <div class="field field-type-text field-field-teaser-article"> <div class="field-items"> <div class="field-item odd"> <p><a href="/issue62/nicholas-et-al#author1">Nick Nicholas</a>, <a href="/issue62/nicholas-et-al#author2">Nigel Ward</a> and <a href="/issue62/nicholas-et-al#author3">Kerry Blinco</a> present an information model of digital identifiers, to help bring clarity to the vocabulary debates from which this field has suffered.</p> </div> </div> </div> <!-- v2, incorporating author review edits inc. lead-ins to bullet lists - 2010-02-12-19-30-rew--><!-- v2, incorporating author review edits inc. lead-ins to bullet lists - 2010-02-12-19-30-rew--><p>Discussion of digital identifiers, and persistent identifiers in particular, has often been confused by differences in underlying assumptions and approaches. To bring more clarity to such discussions, the PILIN Project has devised an abstract model of identifiers and identifier services, which is presented here in summary. Given such an abstract model, it is possible to compare different identifier schemes, despite variations in terminology; and policies and strategies can be formulated for persistence without committing to particular systems. The abstract model is formal and layered; in this article, we give an overview of the distinctions made in the model. This presentation is not exhaustive, but it presents some of the key concepts represented, and some of the insights that result.</p> <p>The main goal of the Persistent Identifier Linking Infrastructure (PILIN) project [<a href="#1">1</a>] has been to scope the infrastructure necessary for a national persistent identifier service. There are a variety of approaches and technologies already on offer for persistent digital identification of objects. But true identity persistence cannot be bound to particular technologies, domain policies, or information models: any formulation of a persistent identifier strategy needs to outlast current technologies, if the identifiers are to remain persistent in the long term.</p> <p>For that reason, PILIN has modelled the digital identifier space in the abstract. It has arrived at an ontology [<a href="#2">2</a>] and a service model [<a href="#3">3</a>] for digital identifiers, and for how they are used and managed, building on previous work in the identifier field [<a href="#4">4</a>] (including the thinking behind URI [<a href="#5">5</a>], DOI [<a href="#6">6</a>], XRI [<a href="#7">7</a>] and ARK [<a href="#8">8</a>]), as well as semiotic theory [<a href="#9">9</a>]. The ontology, as an abstract model, addresses the question 'what is (and isn't) an identifier?' and 'what does an identifier management system do?'. This more abstract view also brings clarity to the ongoing conversation of whether URIs can be (and should be) universal persistent identifiers.</p> <h2 id="Identifier_Model">Identifier Model</h2> <p>For the identifier model to be abstract, it cannot commit to a particular information model. The notion of an identifier depends crucially on the understanding that an identifier only identifies one distinct thing. But different domains will have different understandings of what things are distinct from each other, and what can legitimately count as a single thing. (This includes aggregations of objects, and different versions or snapshots of objects.) In order for the abstract identifier model to be applicable to all those domains, it cannot impose its own definitions of what things are distinct: it must rely on the distinctions specific to the domain.</p> <p>This means that information modelling is a critical prerequisite to introducing identifiers to a domain, as we discuss elsewhere [<a href="#10">10</a>]: identifier users should be able to tell whether any changes in a thing's content, presentation, or location mean it is no longer identified by the same identifier (i.e. whether the identifier is restricted to a particular version, format, or copy).</p> <p>The abstract identifier model also cannot commit to any particular protocols or service models. In fact, the abstract identifier model should not even presume the Internet as a medium. A sufficiently abstract model of identifiers should apply just as much to URLs as it does to ISBNs, or names of sheep; the model should not be inherently digital, in order to avoid restricting our understanding of identifiers to the current state of digital technologies. This means that our model of identifiers comes close to the understanding in semiotics of signs, as our definitions below make clear.</p> <p>There are two important distinctions between digital identifiers and other signs which we needed to capture. First, identifiers are managed through some system, in order to guarantee the stability of certain properties of the identifier. This is different to other signs, whose meaning is constantly renegotiated in a community. Those identifier properties requiring guarantees include the accountability and persistence of various facets of the identifier—most crucially, what is being identified. For digital identifiers, the <strong>identifier management system</strong> involves registries, accessed through defined services. An HTTP server, a PURL [<a href="#11">11</a>] registry, and an XRI registry are all instances of identifier management systems.</p> <p>Second, digital identifiers are straightforwardly <strong>actionable</strong>: actions can be made to happen in connection with the identifier. Those actions involve interacting with computers, rather than other people: the computer consistently does what the system specifies is to be done with the identifier, and has no latitude for subjective interpretation. This is in contrast with human language, which can involve complex processes of interpretation, and where there can be considerable disconnect between what a speaker intends and how a listener reacts. Because the interactions involved are much simpler, the model can concentrate on two actions which are core to digital identifiers, but which are only part of the picture in human communication: working out what is being identified (<em>resolution</em>), and accessing a representation of what is identified (<em>retrieval</em>).</p> <p>So to model managing and acting on digital identifiers, we need a concept of things that can be identified, names for things, and the relations between them. (Semiotics already gives us such concepts.) We also need a model of the systems through which identifiers are managed and acted on; what those systems do, and who requests them to do so; and what aspects of identifiers the systems manage.</p> <p>Our identifier model (as an ontology) thus encompasses:</p> <ul> <li><strong>Entities</strong> - including actors and identifier systems;</li> <li><strong>Relations</strong> between entities;</li> <li><strong>Qualities</strong>, as desirable properties of entities. Actions are typically undertaken in order to make qualities apply to entities.</li> <li><strong>Actions</strong>, as the processes carried out on entities (and corresponding to <strong>services</strong> in implementations);</li> </ul> <p>An individual identifier system can be modelled using concepts from the ontology, with an identifier system model.</p> <p>In the remainder of this article, we go through the various concepts introduced in the model under these classes. We present the concept definitions under each section, before discussing issues that arise out of them. <em>Resolution</em> and <em>Retrieval</em> are crucial actions for identifiers, whose definition involves distinct issues; they are discussed separately from other Actions. We briefly discuss the standing of HTTP URIs in the model at the end.</p> <p></p><p><a href="http://www.ariadne.ac.uk/issue62/nicholas-et-al" target="_blank">read more</a></p> issue62 feature article kerry blinco nick nicholas nigel ward d-lib magazine dest ietf oasis internet archive aggregation archives ark ascii browser cataloguing cool uri cordra curation data database digital object identifier dns document management doi e-learning ftp identifier infrastructure interoperability learning objects metadata mobile mobile phone namespace ontologies openurl persistent identifier purl repositories research rfc search technology semantic web semiotic service usage model uri url vocabularies wayback machine web browser xml xml namespaces Sat, 30 Jan 2010 00:00:00 +0000 editor 1528 at http://www.ariadne.ac.uk