Why is this an important problem ? 
Because we need the ability to manage data across the enterprise
This includes meeting the requirements of new e-commerce applications, such as Corporate Portals. 
In most major enterprises, we have outgrown the data infrastructure. 
That is the major driving force for an Enterprise Data Architecture.
We need a better approach to data integration in order to implement applications quickly and efficiently. 
The demands of e-commerce are really shining a spotlight on the inadequacies of existing approaches to data architecture and integration. 
The Requirement :-
This requirement needs to combine aspects of :-
1) operational systems 
2) decision support systems 
3) legacy systems 
4) new systems, both internal and external
5) data warehouse
It will be very useful when there is a corporate acquisition or merger, and must perform on all hardware platforms, 
operating systems, database systems, and all the other engines of data (such as online analytical processing).
Proposed mergers often have to be aban.d at an advanced stage because of the problems of integrationg IT systems.
The Facilities :-
The Data Architecture should provide the following facilities :-
a) make it easy to identify and source the data needed to support a new packaged application. 
b) make it possible to define a given data element once in the enterprise. 
c) establish the derivation of a given data element from its root sources. 
d) make business rules about data and have them apply across the enterprise. 
Problems of Installing an External System
When a major purchased application is installed, it typically has hundreds or thousands of data element definitions. 
It often must interface to many existing systems, principally to exchange data. 
Managing this in most organizations is a large and expensive nightmare. 
This is frustrating, because we buy applications, rather than build them, so that we can reduce time and cost to implement.