In an ideal world, organizations have enough time, resources, and desire to perform proper planning. They consider the business growth and constraints, and can predict what software applications and systems they will buy in the next five years.

In the real world, organizations may grow by doing mergers and acquisitions, change software vendors, and do no proper planning until it's too late. And this is how it has always been.

Originally, business applications did not allow any integration. Accounting packages, HR software, and CRM applications worked independently. But after a while, the need to be able to use data in another application started looking more and more important.

As an example, let's consider a program that is used to send faxes. The program would have an ability to work with different fax modems, potentially perform fax broadcasting, and would certainly need some sort of address book. It may need to process different types of documents and even be able to embed...