Starting a new thread to answer the question raised in this thread.
Let's start simple and then refine and enhance as our understanding increases.
An aspect is some slice of a project for which you want visibility and communicability. What's mostly talked about are the three main aspects I use which are the PD, UI and the SI. That is, there is a features list and a parking lot chart and a weekly summary report and a trend report and kill sheets and work packages for PD. There is also a features list and a parking lot chart and a weekly summary report and a trend report and kill sheets and work packages for UI. And the same for SI.
Now, you can create other aspects as well or use different ones altogether. The foundation is the features list (FBS) or the list of "trackable items." For each trackable item there is some number of named milestones and a corresponding percentage (FDD happens to enumerate these for PD and SI and it suggests some starting percentages).
From the trackable items and their milestones and from the actual progress (which comes from the work packages) all of the other visibility and communicability items are generated - e.g. the parking lot chart, trend report and so on.
Thus you might also have an aspect for system test or for tech writing and so on (I always do). If you were doing everything by use case, then that would be a aspect (not something I do).
Aspect really is the right word for this. Here's the definition from WordNet © 2003 Princeton University.
aspect n 1: a distinct feature or element in a problem; "he studied every facet of the question" 2: a characteristic to be considered 3: the visual percept of a region; "the most desirable feature of the park are the beautiful views"
All 3 meanings are in play. That we would want the visibility and communicability that the set of FDD artifacts gives, says that this is a characteristic of the project to be considered - a distinct feature of element of the project. And, of course, meaning 3 talks about the visibility and strong visualizations in the FDD artifacts.
Here's a slide from the FDD workshop that makes the point regarding the sets of artifacts produced at each weekly release meeting for each aspect - using only PD, UI and SI for this example. remember, the key point is that you can track anything using the same set of artifacts and whatever that characteristic or distinct part of the project is that you are tracking is what I call a project aspect.