Most applications nowadays are written with menu-driven GUIs (graphical user interfaces). One of the differences of the OPeNDAP Data Connector is that it uses a tab-driven GUI--kind of unusual. The reason for this is that the Data Connector operates in some ways more like a control panel. Menus are fine for document-based systems. In a document-based system there are not a lot complex controls. The user typically just wants to run a simple command like find, replace or execute the spell checker. With the OPeNDAP Data Connector you are not creating a document, you are manipulating a complex system using a series of component-rich control panels. In an ideal world you would present the user with a gigantic control panel with all possible options available, but the limited amount of screen space prevents this. By dividing the control functionality into separate tabs the next best thing to a complete control panel is accomplished.
In the OPeNDAP Data Connector there are actually two levels of tabs: a primary set (Search, Retrieve, View, Help) and a set of dependent tabs underneath that are different for each of the primary tabs. With this kind of system any possible control set is usually one or at most two clicks away. Hot keys for the tabs make it even easier. What this allows the user to do is negotiate the interface much more easily than would be possible with menus.
A disadvantage of a tabbed-driven system is that it takes a little more space because there are two rows of tabs but this disadvantage is outweighted by the one-click convenience the tabs offer.