Advanced Function Presentation has been developped by IBM over many years. From 2006 AFP has been "opened" to a multivendor consortium. See the details at: http://www.afpcinc.org

AFP is actually more than a file format. IBM called it an architecture, that specifies, among other, a set of file formats. See http://en.wikipedia.org/wiki/Advanced_Function_Presentation The main specification concerns MO:DCA.

It takes some time to get used to the jargon. To make things worst, the specification uses the expression "AFP environment" to design a set of former IBM products (software, spooler and printers).

AFP is made of "Structured Fields" (SF), organised in objects. For example, a page is made of a "Begin Page" SF, followed by some SF's, followed by a "End Page" SF.

Inside the Structured Field, there are fixed parameters (fixed: with a fixed length), and/or triplets. Fixed parameters and triplets can be grouped in Repeating Groups.

afppowertools is essentialy a "push" parser that loops over the structured fields. You must register some handlers (callbacks) before you start the parser.