As far as I understood virtual procedures and functions are unbound only in the current implementation in Teiid. Would be nice if there would be a option to have bound (to entities and entity sets) procedures and functions as well.
This would allow for some more syntactic sugar and would allow for a closer integration with libraries such as SAPUI5. See here for an example

https://sapui5.netweaver.ondemand.com/sdk/#/topic/b54f7895b7594c61a83fa7257fa9d13f.html