One of the big problems in a strategic or "enterprise architecture" view of IT is how to model the change in an enterprise's IT portfolio over time. Most of the established modeling techniques, such as those in the Unified Modelling Language (UML), deal with an essentially static view of the system landscape, supplemented by some modelling of the dynamics within systems. These are very poor tools if you are trying to understand how the complete set of systems, technologies and capabilities change over time. The challenge is to add some sort of time axis.
I have found two simple techniques which address this problem. The first is to model the system landscape using some sort of simple "box and line" notation, perhaps as UML packages in a class model. I use a tool like PowerPoint, representing the state at different times on different slides. The trick is to represent corresponding items in the same position and colour on successive slides, and then a simple animation is possible by showing the slides in sequence (or using PowerPoint's own animation tools). The human eye is very good at spotting small changes in a mainly static scenario, or areas of stability in a very dynamic one, so the audience rapidly understands where the change is targeted.
The second technique is the "application roadmap". Here, the X-axis represents time, with different systems or technologies at different points on the Y-axis. The "Z-axis" (different pages) can be used to show different views for different audiences, for example an application-centric, data-centric or technology-centric view. A simple example is show below:
Colour can be used to good effect to represent the type of technology, or the target application/process area. "Banding together" related lines, or varying line styles can represent further dimensions, so that this can become an extremely rich model if required.