Path Analysis in Visio
The well-commented VBA code (provided by guest-poster Al Edlund) which accompanies this article will help you make programmatic sense of the elemental stuff of connected Visio diagrams: connectors, connection points, OneD shapes, Connect and FromConnect.
You’ll also see how to produce connected diagrams, find out which shape is connected to which, and more importantly, do some path analysis to find the deeper meaning behind it all!
This guest post was developed and written by Al Edlund. Al is a fellow Microsoft Visio Most Valuable Professional (MVP), and is a networking expert, and a big fan of Visio. He’s also told me that networking is also his hobby, so when he’s working he’s playing, and when he’s playing he’s working!
Thanks Al for a great effort, now take it away!
Connectors, Connections and Paths
I have seen a couple of recent requests that have focused on how to understand what is connected in a Visio drawing. What is sometimes missed is that there is a difference between connected and a path, which is a series of connections. This path deconstruction is sometimes referred to as graph analysis and is the study of how nodes (vertexes) attach to each other via “edges”.
What is sometimes overlooked by the user who wants to analyze the drawing via automation is that there are two levels of domain specific knowledge that are needed. The first is what is being represented by the shapes on the page and the second is how the underlying add-in portrayed that information.
This led me to a put together a two-part project which you can read about in these pages, and download when you’re done with the words. The project focuses on these two items:
- Demonstrates some concepts in analyzing a drawing’s connections
- Analyzes the path information
Using the Path Analysis Application
Once you’ve OK’d the VBA macros in the Visio file and clicked the StartTest button on page one, you’ll be presented with the project’s main form:
Figure 1 Example Menu layout
The path analysis form has two groups. The left one is for demonstrating path analysis and the right one is for drawing (connection) analysis.
The path analysis has three sections: the analysis algorithm, the view layers, and the open Excel button. The analysis algorithms create topology pages to demonstrate search techniques. The edge information and path search information are drawn on different layers which can be turned on/off by the layer buttons. The Open Excel feature is included to allow the user to pull in external data. The description of the workbook/worksheets is included in the code module: modDrawData.
The ConnectionsSearch section has four buttons. Flowchart draws the modified Visio 2007 SDK navigation example. The Drawing button uses the included page connection search to capture the active page connections. The Network button discovers the data from the network page, and the PFD button discovers the data from the pipes/flow/diagram. Lastly, the Save2Excel8 button takes the data from the last analysis and exports it to an Excel2003 format.
The Visio SDK has an example of analyzing a drawing (DemoNavigatingDrawing) which combines both of these concepts (connection analysis and path analysis).
I’ve included a modified version of this flowchart analysis in the drawing.
Figure 2 Flowchart Example used
The modifications include:
- Adding an additional data entry function
- Including a control transfer shape.
I added these to demonstrate that:
- In a drawing that is aware of the ‘directionality’ of dynamic connectors the developer may have to adopt a strategy that verifies that all shapes have been included
- Shape.Type = OneD shapes which are not ‘Dynamic connectors’ may be in the information path.
I’ve included a network detail drawing as well which brings out a couple of other exposures. In this case the points that require attention include (once again) that OneD shapes may not necessarily be part of an information flow and (to make it a little more interesting) we have to track connector end-points based on their component and connection point.
Finally in the network connections the paths are assumed to be capable of ‘full duplex’ communications which removes the directionality aspect.
Figure 3 Network Detail Drawing used
Piping Flow (PFD)
The example of a piping flow drawing (provided by another user) as starting points has three sets of objects we want to track. These are equipment (vertices), piping (edges), and instrumentation (probes). The interesting point here is that a probe attaches to a OneD shape (pipes) in the example drawing.
Figure 4 Piping-Flow diagram used
Both the network detail and PFD drawings also demonstrate that you have to be aware of the underlying add-in that created the drawing. In the case of the PFD drawing shape text is stored in a user field.
The captured data from the connection analysis can be saved to an Excel spreadsheet. Excel in this code is 2007 Excel and doesn’t do a lot of checking or error catching. It is there for convenience.
Figure 5 Excel Output (PFD drawing)
Path Analysis (Depth-first)
The second part of the project was to demonstrate some of the common methods for analyzing path information. The basic flows are excerpts from Data Structures and Algorithms Using Visual Basic.NET, a Michael McMillan book that was written for VB.NET.
I thought it would be fun to convert the concepts to VBA and then use Visio to draw the constructs and use layering to show how the algorithms worked. The data is based on two mandatory arrays (vertex and edge) and an optional array that allowed me to force some of the shapes to specific places on the page. A tutorial on this material goes well beyond what an article can cover. Mr. McMillan’s book is also referenced in the code.
Figure 6 Path Analysis (depth first)
This code should not be considered as anything beyond demo code of some advanced concepts. When you open Visio’s VBA integrated development environment, you’ll see the following forms, modulas and classes:
Figure 7 Application objects
Here’s a quick description of what each code file is about:
- frmPath user interface
- modDrawData the information used to initialize the three main arrays used to create the drawings used in the path analysis section
- modFlowchartNavigator the basic code used in the v2007 sdk that demonstrates an approach to moving through a visio flowchart
- modNavEnhanced an example of how analyzing a drawing might be enhanced using the two examples provided (Network Detail and PFD)
- clsDistOriginal object storage
- clsItemEdge object storage
- clsItemPoint object storage
- clsItempProbe object storage
- clsVertex object storage
- clsShapePos object storage
- clsMyCollection string / array manipulation
- clsMyGraph path analysis code