Tracing drivers with smart results in the Editor

Like any software modelling tool, STEM is great when it does what you want: it saves time, enforces consistency, and avoids stupid errors. However, it can be frustrating if it doesn’t behave as expected/required. Not only should you trace routinely through the relevant results for each element to verify that all is as intended, sometimes you have to do this if you can’t figure out why the results are the way that they are!

It doesn’t help that you have to switch to the separate Results program, and then locate the relevant elements all over again in the graph-drawing interface (however nice the new interface is). You even have to think about which results are most relevant. While both aspects of this process become second nature to an experienced modeller, we should not overlook the number of mental leaps required here, especially for the uninitiated.

Fast track to results in the Editor

We are now developing the capability to display results directly in the Editor. Rather than switching to a separate window and then re-locating the relevant elements in a list, you will be able to draw results charts directly from the context menu for an icon, or for a multiple selection of elements, in the Editor.

1. Right-click one of the icons to select the context menu, and then look for a new cascading sub-menu called Results. The sub-menu offers all of the Essential results which are available for the selected elements (even with a variety of element types).
2. Select one of these results. A single new graph is drawn immediately below showing the selected result for each of the selected elements.

Figure 1: Graphing an essential result directly from an element in the Editor

The graph is created as an entity within the current view which can be moved around or resized, just like a textbox. It will be selected when first drawn so that it can be readily discarded (by pressing <Del>) if you only want to review the results temporarily.

A graph drawn this way will show the most recently-run scenarios by default, or possibly the same scenarios as selected most recently for another chart. We may make it so that these scenarios are sliced (from a dropdown on the chart) if more than one element is selected and thus represented on the chart.

You can then modify the graph format in situ by right-clicking the graph as you do in the current Results program, or change the selection of elements, results or scenarios by right-clicking the title or legend items as appropriate. The Editor will prompt to re-run any extra scenarios which are currently out-of-date.

The more familiar Draw commands will also be available from a new Results dropdown on the main menu-bar if you prefer to specify everything in advance. We might also add a Select Results option to the context menu which would jump from the iconic selection of elements to the next tab in the regular graph Draw dialog.

Results graphs and tables can be placed alongside the relevant icons, or in separate views if you prefer, and they will scale together with the icons when you change the Zoom level. As a selectable item in its own right, a graph can be readily copied. This offers a potentially more intuitive alternative to the current Draw Similar command (for cloning a graph) and also makes it easy to duplicate a whole selection of graphs in another view.

Note: we could add a Cut command to make it easier just to move a selection from one view to another by automatically removing the original items after they are pasted.

All of these actions, from drawing a graph to modifying it in situ, or moving or sizing it within or between views, will be reversible with the general Undo system in the Editor.

Figure 2: Specimen hybrid input and results view

The Editor will load an existing results workspace, and it will still be possible to include the results of other models if so desired. All the usual results options will be accessed from the existing Options menu in the Editor. The long-term aim is to retire the separate Results program altogether, though it is likely that we will retain it at least long enough for people to become familiar with the new interface and embrace it rather than being forced to adopt it involuntarily!

This integration of functionality from the current two separate programs will be a defining feature of the forthcoming STEM version 8.0.

Graphs that you might like to draw

The most important results graphs are now just a few clicks from the relevant model elements in the Editor. It’s a bit like the immediacy of shopping on Amazon or surfing on YouTube… except that they make it even easier by anticipating what you might want to buy or watch next.

Suppose that STEM could also guess which results would be of the most immediate interest? Considering the usual advice from training about tracing routinely through the relevant results for each element, it is easy enough to determine which results are most pertinent to the flow of calculation in terms of the underlying drivers. Experienced modellers have checked these results, laboriously, for years; and now we are going to make it so much easier with a simple command that must be seen to be believed!

So far we have been focused on accessing results for individual elements, whereas most of the significant calculations in STEM arise from the connections between elements. Imagine (as follows) that you could also look for results on the menu for a connection between two elements, or on the icon menu for a selection of connected elements, or even for two distant elements where an indirect connection exists or is suspected.

1. Right-click a connection between two icons and then select Trace Results from the context menu. STEM automatically draws the most pertinent graph for each element based on the nature of the connection between them (e.g., service Connections and resource Capacities for a requirement link). The two graphs thus created appear side-by-side below the elements.
2. Right-click a multiple-selection of icons (at least two) and then select Trace from the Results cascading context submenu mentioned above. STEM more generally graphs the ‘input and output’ of each direct connection within the selection, skipping the input for intermediate elements where this is the same result as already graphed as the output for a preceding connection.
3. Select exactly two icons and then select Trace from the Results cascading submenu. STEM more extensively and helpfully identifies any direct or indirect connection between the two elements (which could be obscured across multiple views), and again charts all of the intermediate drivers as well as the initial assumption and final result.

Figure 3: Tracing the flow of calculation for a single connection or between multiple elements

Which results would you check when a service has a requirement for [capacity from] a resource? Which results would you check when a location controls the deployment of a resource? And which results would you check when a resource is an input to a transformation?

One always checks more or less the same charts, depending on the exact relationship between the various connected elements. Usually one pertinent result ‘from each side’ will be sufficient to illustrate the calculation flow as detailed in Figure 4 below.

Figure 4: Connections between elements and the corresponding results to graph when tracing

If more than two graphs are created, then they are cascaded for compactness, and can be easily stepped through by clicking the corners. At first the newly-created graphs will all be selected and therefore easy to delete. Stepping through the individual graphs will lose the selection, but it will still be possible to press <Del> repeatedly to discard them, one at a time, as the focus is always passed to the most recently-selected item when the current item in a view is deleted.

Making STEM more immediate and intuitive to use

Now we can literally trace the flow of calculations in a model. You no longer need to switch to a different window and re-locate the relevant elements in a list, and now STEM will even do all of the routine checking for you! Removing mental leaps such as these is a central design objective for the forthcoming STEM version 8.0.

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