Ganesh Prasad:

In the realm of identity management, I realised that any given entity has no inherent properties (attributes) at all! All attributes that an entity may be deemed to have are only by association (just as a particle acquires mass independently of its existence), and therefore the only necessary aspect of an entity is a unique and meaning-free identifier to set it apart from other similar entities. Attributes can then be assigned and de-assigned to it at will through the mechanism of the identifier, and gradually a more sophisticated model can be built up. In creating such sophisticated models, it’s important to remember that nothing is inherent to an entity, - not first name/last name, not primary email address, not social security number, - nothing! Just a unique identifier that is internal to the domain and kept invisible to the world outside the domain.