Recap of P: Message Processing Language Presented by Abbie Barbir

August 3, P: Message Processing Language P is a simple configuration language designed for specification of message processing instructions (service) at application proxies –P can be used to instruct an intermediary on how to manipulate the application message that is being processed Original draft work was submitted by –Alex Rousskov ( ) and –Andre Beck ( ) draft-ietf-opes-rules-p-02

August 3, P Design Objectives P language primary objective is to express statements similar to: –If message meets criteria C, –Then apply service S; P programs mostly deal with formulating message- dependent conditions and executing authorized services P design is meant to be applicable for a variety of similar intermediary configuration tasks such as –Access Control List (ACL) specification –Message routing in proxy meshes or –Load-balancing environments

August 3, Characteristics of “P” P is a single-assignment, lazy evaluation, strongly typed functional programming language Centered around the concept of an “object”, similar to objects of object-oriented languages An object is, essentially, a piece of data or information Value of an object is indistinguishable from the object itself Object type is defined by the semantics of applicable operations and manipulations Almost everything in P is an object, even a piece of code General approach is application protocol agnostic –Supports loadable modules for adding support of (existing and new) application protocols

August 3, Open Issues/Problems What (message) information can the P interpreter access, i.e. what information can be part of a rule condition? For example: –Complete message (including message body), –Meta-information only (e.g. HTTP headers only), –Where to draw the line? –Does the WG have to specify this? Should the WG document an HTTP module for P? –If yes, in what document? Should the WG define interfaces between P interpreters and module suppliers and/or callout services? –How do services return results?

August 3, Q&A