Action Scripting Question - Leaving Current Values Alone

Hi,

I'm very new to the land of scripting for Photoshop. I've a ton of experience working with .NET, but not a lot on JavaScript, or the Photoshop object model. I've managed to work out what I need to change from the script listener output and I think I've a handle on what it is doing, but not quite whether I can pick and choose! So, the way I'm reading the script is;

First variable obtains a pointer to the object that is to be manipulated

The action descriptor variables then seems to build the new property values

Am I right in assuming that if you don't "put" a new value into one of the property elements it will retain its original value when it is passed into the execution action?

Thanks,

David