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The Identity Metasystem

We can now count on the laws of identity as guidance and as a powerful tool for evaluating whether a solution is truly fit for the task. The time has finally come to unveil a comprehensive, long-term solution to the problems we have described so far.

Of all the seven laws, many are actually just good architectural common sense. The fact that there was the need for a law to be formulated reflects the fact that the Internet grew like a coral reef, without an architect, and things just happened on their own. The tools for solving many of those problems are available and are successfully used in other areas; it's just a matter of engineering them in the identity space.

One law, however, is problematic: the "Pluralism of Operators and Technologies." We have made clear throughout the entire book that diversity is an important and a noneliminable component of the Internet ecology. How can we convince that all entities in operation, today and tomorrow, would abandon their current systems and adopt a new one? Would we even want to do such a thing?

Fortunately, we don't need to. We can create a system of systems, or Metasystem, that will embrace existing technologies and facilitate the dialog among them.

Managing identity entails manipulating common abstract principles, performing specific actions and covering canonical roles. Those are concepts that exist in complete independence of the specific features of the existing and imaginable authentication schemes. Just think of the descriptions we gave of SAML, Kerberos, Secure Sockets Layer (SSL) client authentication and others in the section "The Babel" in Chapter 1. There are important differences in the way they operate, but you can see that there are analogous concepts (such as the idea of token) and messages with the same semantic (such as obtaining a token from an authority).

We can conceive an Identity Metasystem that defines concepts and operations universally valid in the identity space, without bothering about the implementation details; we can devise an integration layer through which the peculiarities of specific identity systems are abstracted out and mapped to and from those generic constructs. Not having an implementation on its own, the Identity Metasystem does not aim to substitute for existing systems. It actually needs them because they provide the implementation fabric it lacks.

This solution enables applying what we have learned about correct identity management without compromises because we don't have to worry about legacy features we need to maintain for the sake of technology. At the same time, the solution invites present and future technologies to participate. By concentrating on the fundamental principles of identity management and leaving the details to single solutions, it is impervious to technological dependencies that would limit its scope and its expected life.

This simple idea has beautiful implications and defines the very physical laws of the universe in which Windows CardSpace is meant to operate. The remainder of the current section describes in depth the Identity Metasystem, introducing many concepts and ideas that are key to understanding the technology.

The section "Some Definitions" formalizes some of the terms used in the context of the Identity Metasystem.

The section "Roles in the Identity Metasystem" describes the essence of the solution by introducing the entities and the relationships that keep together the ecology defined by the Identity Metasystem. The discussion will still be at the model level, without strong references to the actual reification of the solution in today's technology landscape.

The section "Components of the Identity Metasystem" digs deeper into the requirements that must be satisfied for making one Metasystem possible. It will also lay the foundation for the section "WS-* Implementation of the Identity Metasystem" later in the chapter.

Some Definitions

The content of this section is long overdue. Through the book, we introduce numerous concepts that are peculiar to the identity management space. However, we have tried to avoid as much as possible the usage of many of the loaded terms that you find in the literature. It was not easy, but we hope that this model favors the unbiased understanding of the new ideas we are discussing.

It is now time to define more rigorously some of the terms we have been using loosely and substitute some of the words we used with specific identity-related terminology. We will not give all the definitions here, but we will keep introducing new concepts as appropriate throughout the rest of the book. For example, the definition of subject is delayed until the section "Roles in the Identity Metasystem," where the context is ideal to understand its function and importance.


A claim represents a fact about something or somebody. Better. A claim is a statement that a certain fact applies to something or somebody. As such, it is subject to verification. In other words, you can accept or reject the claim based on your beliefs, knowledge of the situation, and so on. Classical examples of claims about people are "Bob was born in 1956," "Bob is a Belgian citizen," "Bob belongs to the 'Managers' user group at Contoso.com," "Bob has green eyes," "Bob can buy $5000 worth of merchandise," "Bob is really the one who received this ticket from the TGS." Claims about things are no different: "Contoso's public key is Fx0Ex0...," "Contoso has its main office in Las Vegas," and so on.

Those claims may or may not actually apply to Bob or Contoso. The way in which you get to decide one way or the other accounts for a good part of the entire identity management process.

(Digital) Identity

As central as this concept may be to the topic of this book, the definition of (digital) identity is largely unimpressive:

A (digital) identity is a set of claims made by a subject about itself or another subject.

In the section "Roles in the Identity Metasystem" we will see what we mean exactly by subject, abbreviated S. For the time being, you can just substitute the occurrences of the word in the definition with the same "somebody or something" we used in the section "Claim."

Remember the discussion about the difference between credentials and digital identity in section "HTTPS, Authentication, and Digital Identity" from Chapter 1? The airline example should have provided an intuitive idea of what we mean by identity in this context. Now that we have a definition, we can refine the concept a bit further.

One thing you might notice from the definition is that an identity is made up of claims all coming from the same source; given the fact that claims may or may not actually apply, what you know about that source may influence what you believe to be true for the entire identity as opposed to considering claims one by one. There will be more (much more) about this later in the section.

Another interesting thing you may notice from that definition is that an identity can be self-asserted. It is perfectly legitimate for somebody to make claims about himself. This actually happens all the time on today's Internet. When you sign up for an Internet service and you are asked to fill in a profile, you are making claims about yourself. Again, this is an important consideration and will be explored at length later in the book.

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