An Overview of the K Framework. Grigore Rosu University of Illinois at Urbana Champaign (joint work with Traian Florin Serbanuta)

Transcription

1 An Overview of the K Framework Grigore Rosu University of Illinois at Urbana Champaign (joint work with Traian Florin Serbanuta)

2 Challenges in Programming Language Design / SemanIcs / Analysis Programming languages are coninuously born, updated and extended C#, CIL; Java memory model, Scheme R6RS, C1X Concurrency is the norm, not the excepion Executable specificaions could help Design and maintain mathemaical definiions Easily test/analyze language updates/extensions Explore/Abstract non determinisic execuions

3 K Project Started in 2003, moivated mainly by teaching programming languages and noicing that the exising semanic frameworks have limitaions Project thesis: RewriIng gives an appropriate environment to formally define the semanics of real life programming languages and to test and analyze programs wri[en in those languages.

4 Overview RewriIng logic semanics project How it all started... K framework K definiional style K concurrent rewriing Example Challenge language

5 RewriIng Logic SemanIcs Project RewriIng Logic (RWL) Meseguer 1992 RewriIng Logic SemanIcs (RLS) Project Advance the use of rewriing logic for defining programming languages, and for execuing and analyzing programs wri[en in them ParIcipants (probably incomplete list): Wolfgang Ahrendt, Musab Al Turki, Marcelo d Amorim, Irina M. Asavoae, Mihai Asavoae, Eyvind W. Axelsen, ChrisIano Braga, Illiano Cervesato, Fabricio Chalub, Feng Chen, Manuel Clavel, Chucky Ellison, Azadeh Farzan, Alejandra Garrido, Mark Hills, Michael Ilseman, Einar Broch Johnsen, Ralph Johnson, Michael Katelman, LaurenIu Leustean, Dorel Lucanu, Narciso Mard Oliet, Patrick Meredith, Jose Meseguer, Elena Naum, Olaf Owe, Stefan Reich, Grigore Rosu, Andreas Roth, Juan Santa Cruz, Ralf Sasse, Wolfram Schulte, Koushik Sen, Andrei S,tefanescu, Mark Oliver Stehr, Carolyn Talco[, Prasanna ThaI, Traian Serbanuta, Ram Prasad Venkatesan, Alberto Verdejo

6 Why is RewriIng Logic Good for Programming Languages? Executability Language definiions turn into interpreters Concurrency The norm rather than the excepion EquaIonal abstracion Collapse state space through equaions Generic tools (built around Maude) ExecuIon, tracing, debugging, state space search, model checker, inducive theorem prover

7 Guidelines for Defining Programming Languages in RWL Represent program state as configuraion term Represent computaional steps as rewrite rules Represent structural changes as equa-ons These associate to any given configuraion a transi-on system In paricular, it associates semanics to programs ResulIng transiion systems are amenable to exploraion, search and model checking Great, but it does not tell us how to do it

8 ConvenIonal semanic frameworks become RWL definiional methodologies This allows to define a language using one s favorite semanic style, and then to execute, explore or model check it using RWL

9 ConvenIonal semanic frameworks become RWL definiional methodologies Many authors contributed to this diagram, including all the abovemenioned. See [Serbanuta, Rosu, Meseguer 2007 Inf. & Comp.] for a recent survey. This allows to define a language using one s favorite semanic style, and then to execute, explore or model check it using RWL

10 ExisIng SemanIcs Frameworks, From a Unified PerspecIve The unified view of semanic frameworks within RWL also allows to be[er examine them and understand their limitaions For example, can exising styles define real programming languages on a regular basis, as opposed to only toy languages? No, but their combined strengths might

11 Shortcomings of ExisIng Frameworks Hard to deal with control (except evaluaion contexts) halt, break/coninue, excepions, callcc Non modular (except Modular SOS) Adding new features require changing unrelated rules Lack of semanics for true concurrency (except CHAM) Big Step captures only all possible results of computaion ReducIon approaches only give interleaving semanics Tedious to find next redex (except evaluaion contexts) One has to write the same descent rules for each construct Inefficient as interpreters (except for Big Step SOS)

12 Towards an Ideal PL DefiniIonal Framework Our iniial goal was to search for an ideal language definiional framework within RWL At least as expressive as evaluaion contexts At least as modular as Modular SOS At least as concurrent as the CHAM

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