Digital Identity is the representation of Identity in terms of digital information.

Digital identity is the ubiquitous existence of an Entity.

Digital identity = Virtual Entity (Spanish language audio resource)

A digital identity can be understood as the set of digital information that is attributable to any given Entity. This entity may be human (an individual or a community), a physical object, or even digital information itself.

Not having or having a digital identity could become a new Human Right (see Human Rights).

A Digital identity could also become a new Legal entity in the future. Justicia Social por medio de la Entidad Virtual.pdf (Spanish language PDF).

A digital identity is composed of Presence/Omnipresence, Attributes/Content/Information and Projection. (Spanish language PDF)

Identity through relationship

An observer's perception of the digital identity of an entity is inevitably mediated by the subjective viewpoint of that observer (just as it is with physical identity). This becomes clear when one considers the implications of the concept of "Attribution" within the definition: in order to attribute information to an entity, the attributing party (the observer) must trust that the information does indeed pertain to the entity (see Authentication below). Conversely, the entity may only grant the observer selective access to its informational attributes (according to the identity of the observer from the perspective of the entity). In this way, digital identity is better understood as as a particular viewpoint within a mutually-agreed relationship than as an objective property.

Authentication

Authentication is a key aspect of trust-based identity attribution, providing a codified assurance of the identity of one entity to another. Authentication methodologies include the presentation of a unique object such as a bank card, the provision of confidential information such as a password or the answer to a pre-arranged question, the confirmation of ownership of an email address, and more robust but relatively costly solutions utilising Encryption methodologies. In general, business to business authentication prioritises security while user to business authentication tends towards simplicity. New physical authentication techniques such as iris scanning, hand-printing and voice-printing are currently being developed and in the hope of providing improved protection against Identity theft.

Ontologies of identity

Digital identity attributes—or data—exist within the context of ontologies (see Ontology (computer science)). A simple example of an ontology is "a cat is a kind of animal". An entity represented in this ontology as a "cat" is therefore invariably also considered an "animal". In establishing the contextual relationship of identity attributes to one another, ontologies are able to represent identity in terms of pre-defined structures. This in turn allows computer applications to process identity attributes in a reliable and useful manner. XML (eXstensible Markup Language) has become a de-facto standard for the abstract description of structured data.

Ontologies inevitably reflect culturally and personality relative world views (see Cultural relativism). Consider two possible elaborations of the above example:

1) "A cat is a kind of animal. A domestic cat is a kind of cat and is a pet" 2) "A cat is a kind of animal. A domestic cat is a kind of cat and is edible by humans"

Someone searching ontology 1 for pets would find "domestic cat", whereas a search of ontology 2 for foodstuffs would yield the same result! We can see that while each ontology is useful within a particular cultural context or set of contexts, neither represents a universally valid point of view on domestic cats.

The development of digital identity network solutions that can inter-operate ontologically-diverse representations of digital identity is a contemporary challenge. Free-tagging has emerged recently as an effective way of circumventing this challenge (to date, primarily with application to the identity of digital entities such as bookmarks and photos) by effectively flattening identity attributes into a single, unstructured layer. However, the organic integration of the benefits of both structured and fluid approaches to identity attribute management remains elusive.

Networked identity

Identity relationships within a digital network may include multiple identity entities. However, in a decentralised network like the Internet, such extended identity relationships effectively require both (a) the existence of independent trust relationships between each pair of entities in the relationship and (b) a means of reliably integrating the paired relationships into larger relational units. And if identity relationships are to reach beyond the context of a single, federated ontology of identity (see Ontologies of identity above), identity attributes must somehow be matched across diverse ontologies. The development of network approaches that can embody such integrated "compound" trust relationships is currently a topic of much debate in the blogosphere.

Integrated compound trust relationships allow, for example, entity A to accept an assertion or claim about entity B by entity C. C thus vouches for an aspect of B's identity to A.

A key feature of "compound" trust relationships is the possibility of selective disclosure from one entity to another of locally relevant information. As an illustration of the potential application of selective disclosure, let us suppose a certain Diana wished to book a hire car without disclosing irrelevant personal information (utilising a notional digital identity network that supports compound trust relationships). As an adult, UK resident with a current driving license, Diana might have the UK's DVLA vouch for her driving qualification, age and nationality to a car-rental company without having her name or contact details disclosed. Similarly, Diana's bank might assert just her banking details to the rental company. Selective disclosure allows for appropriate Privacy of Information within a network of identity relationships.

See also: Pseudonimity