There are 2 file types use the .VSL file extension:
1. Visio Add-on
Addon, or library, file used by Microsoft Visio, a business diagramming application; saves software components that extend the functionality of the program; typically created and distributed by third-party developers.
NOTE: VSL files are actually .DLL files that are specifically configured to run with Visio.
Updated: July 30, 2012
2. Velocity Template File
Developer file used by Velocity, a Java template engine used to auto-generate text and source code; contains text as well as statements written in the Velocity Template Language (VTL); often used for generating Web page source code.
Velocity enables data from a Java program to be merged with a Velocity template to produce an output text file. For example, an HTML file that is a Velocity template may have an unpopulated table that is populated with data when run with a Java program using Velocity.
NOTE: Velocity templates more commonly use the .VM extension.
Updated: January 3, 2011