Hi,Can any one point out in which Expression jar i can find out getProperty() fu

Mohan, are you by any chance referring to the property() function? If so, it is a built-in Appian function: forum.appian.com/.../Scripting_Functions

If you know (or kind-of-know) the name of the property, you can simply open up the expression editor and start typing it to get the detail and documentation. The categories are pretty-much self-explanatory. In case you are stuck, work on eliminating those categories where it can't be there thus leaving you with a smaller set to find out where it is.
As always, Appian Documentation is a great place to look as well.