From an OO viewpoint, there is no concept of data existence, independent of function, within any IT architectural perspective from conceptualization through realization. The notion of a class is the fundamental building block of object orientation. Persistence forms the infrastructure of a business organization's information assets. Persistent data exists independent from processing. Whereas one of the primary objectives of object orientation is reuse of software, data is, without a doubt, one of the most highly-reusable assets of a business organization.
Businesses ignore the benefits of enhanced data reusability at their peril.
Many other established analysis and development approaches do indeed consider the data resource of a business independent of the functions to which it interfaces. A number of side effects result from marginalizing the independent existence of the data resource, mostly to the detriment of precision of specifications. These include ambiguity in specifications for data resources themselves, and ambiguity in defining interfaces among data and between data and functions. Because there is no recognition of data independent from function, there is consequently no recognition of a data-function interface. An interface is a boundary between two independent things, and if data and function are not independent, the notion of a boundary between them has no meaning.