While EDI is a documented standard, the technologies needed to implement it are expensive and require extensive customization and programming. Thus, EDI is used mostly in very large organizations with considerable IT budgets and internal resources. In contrast, XML is far less expensive and cumbersome, opening the door for small, low-tech companies to participate in online data exchange with their partners. Assuming all the trading partners in an industry or vertical market use the same DTDs, these partners can trade data seamlessly, with little need for additional customization or integration. To this end, some industries have formed consortiums to define standard DTDs for documents commonly exchanged in their industries.
Interoperability is one of the biggest bangs for the buck that XML offers.
This includes enabling internal systems to share data with each other, as well as enabling companies to share data with external business partners. Internally, using XML makes it easier for data in multiple disparate systems to be used together or shared in a common application. For example, organizations may have one legacy system for customer information, and another for accounting and billing functions. By generating XML output from a given system, the data can be shared with different systems or custom applications in order to bring the disparate systems together. Thus, XML can save major time and effort in integrating internal systems via traditional programming and custom integration methods.