Rules Tools was written by David J Parker to surface the validation rules within Microsoft Visio 2010 Premium edition. There is an accompanying book, Microsoft Visio 2010 Business Process Diagramming and Validation (see https://www.packtpub.com/microsoft-visio-2010-business-process-diagramming/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://bvisual.spaces.live.com
David J Parker has been a Visio MVP for many years.
Visit https://mvp.support.microsoft.com/profile/David.John.Parker for more information.