Multiple document interface or MDI is a programming strategy that is commonly part of the Windows experience. Essentially, this type of interface makes it possible for users to work with several different documents simultaneously. For example, an end user may have both two spreadsheets and two word processing documents open and resized to appear side by side on the computer monitor screen. This allows the user to easily move back and forth between the two different documents.
Multiple document interface is much like the Windows desktop interface that allows the user to line up multiple application windows on the desktop. With the desktop interface, the user may have a mailbox, a word processing document, and a spreadsheet all open at the same time. Multiple document interface allows the same type of functionality, just within the confines of a given application that is referred to as a client area.
The actual process of multiple document interface involves what is known as a parent and child environment. Essentially, the document application proper functions as the parent, and provides the viewing space for the individual documents. Each document that is open is viewable in what is known as a child window. The child windows may be reduced in size so that several can be viewed at the same time. This allows the user to cut and paste data from one document to the next with very little effort.
The ability to view multiple documents can be effective in carrying out tasks associated with work. Multiple document interface can also be helpful in environments where a web conferencing tool is utilized to share a desktop. The moderator of the web meeting can make use of this function to share multiple documents with attendees of the conference, effectively allowing everyone to see the open window of the common application.
Another example of an MDI application is the ability to view two versions of the same presentation side by side. This ability can be very helpful when drafting a response to a Request for Proposal. By having the RFP open in one window and the response document open in a second window, it is much easier to follow the format preferred by the request and thus increase the chances of providing specific answers in the order and structure requested.