When most commerce was transacted face to face, the question of identity was simple. Our brains, hardwired to process the evidence of our senses, made the judgment. Our appearance, voice, the way we shake hands, even the way we smell, all served to identify us to others. Our identity was a combination of these characteristics, or attributes.

Computer systems don't have our senses, but our attributes still define us. A user identity is a collection of data that describes us to the systems we use every day, including attributes such as names, addresses, employee ID numbers, and social security numbers.

However, as the number of servers, databases, and applications ("services") multiply in a company, the problem is not whether we have an identity, it's that we have too many of them.

Multiple user identities are creating problems in organizations. A rapidly growing category of software, Identity Management (also known as IdM), is designed to solve these issues.