In addition to the ”why”, it is important to define the “what” in an architecture. This is the third element of the architecture vision statement. By defining what is meant by architecture, the organization has a clear understanding of what architecture is; which aspects are included and what form the architecture should take.
There are a number of definitions of architecture, for instance IEEE 1471, IAF and of course DYA. It is not important which one is used, as long as it is the most appropriate for a specific organization.  In every instance, the objectives should be reviewed and the most fitting definition applied.

IEEE 1471
The definition of IEEE 1471-2000 is broadly accepted as the starting point for architecture: “the fundamental organization of a system embodied in its components, their relationships to each other, to the environment and the principles guiding its design and evolution” .

IAF
Rijsenbrij et al define architecture as “a coherent, consistent collection of principles and models, specialized to precepts, rules, guidelines and standards – sometimes documented in patterns – that describe how a business, the data supply, an information system or an infrastructure is defined and how it is presented in operation”.

DYA
Wagter et al use the following definition of architecture: “a consistent compilation of principles and models that define the direction of a design and implementation of the processes; organizational structure; data distribution and technical infrastructure of an organisation”.

When selecting a definition for a particular organization, it is important to select one that gives the most concrete definition of architectural nature and scope. Should architecture be limited to IT, it is important that this be indicated in the definition. Should architecture be used soley to define principles and standards that define the design direction, then only this should be included in the definition.