Rules Tools was written by David J Parker to surface the validation rules within Microsoft Visio 2013 Professional edition. There is an accompanying book, Microsoft Visio 2013 Business Process Diagramming and Validation (see http://www.packtpub.com/microsoft-visio-2013-business-process-diagramming-and-validation/book , which explains the how to analyse existing validation rules and how to write custom validation rules.
Access to the relevant websites is available on the About button drop-down menu.
About button drop-down menu
Visio Rules website - http://www.visiorules.com/
bVisual website - http://www.bvisual.net/
bVisual blog - http://blog.bvisual.net
David J Parker has been a Visio MVP for many years.
Visit http://mvp.microsoft.com/en-us/mvp/David%20John%20Parker-21090 for more information.