We've worked on one key area of abstraction - the form interface.  We see forms as the cornerstone of all applications, the linchpin for getting data into systems (and out of them, via reports, which can be seen as a type of form).  We wanted to be able to have the system generate HTML forms using a specification that was itself defined and controlled in Presto, down to a field-by-field level.  At the very least this is a quality control measure - enabling code for forms to be generalised and improved for all forms across the board in a particular Presto installation, or in the upgrade of all installations. 

Presto's form interface is a central part of our application development toolset, since the forms can be made to do a variety of things, from sending their own content via email, to logging their content to text files, XML, and to database records.