MDS stand for Mobile Data System (BlackBerry MDS). It’s a method of Internet connectivity for a BlackBerry. that is provided by a BlackBerry Enterprise Server. In the past, BlackBerry devices required MDS to run most kinds of third-party Internet software.

BlackBerry MDS v4.1 is an optimised application development framework for the BlackBerry® Enterprise Solution. It dramatically reduces the amount of time and resources required to develop and deploy wireless applications for mobile workers. BlackBerry MDS allows organisations to deliver corporate data wirelessly, leveraging the same proven push delivery model and advanced security features used for BlackBerry email.

BlackBerry MDS components and architecture
BlackBerry MDS provides the essentials for creating, deploying and managing applications for the BlackBerry Enterprise Solution. Its three main components are:

1. BlackBerry MDS Services
   BlackBerry MDS Services are the next generation of the BlackBerry® Mobile Data Service. As part of the BlackBerry® Enterprise Server, they are responsible for managing interactions and requests between BlackBerry smartphones and enterprise applications that sit behind the corporate firewall.
2. 2. BlackBerry MDS Developer Tools
   Use BlackBerry MDS Developer Tools to create wireless applications for BlackBerry smartphones.
3. BlackBerry MDS Device Software
   BlackBerry MDS Device Software allows applications built with BlackBerry MDS Developer Tools to run on BlackBerry devices.