Vasco T. Vasconcelos

Diogo Poças, Gil Silva, Vasco T. Vasconcelos

We provide an algorithm for deciding simple grammar bisimilarity whose complexity is polynomial in the valuation of the grammar (maximum seminorm among production rules). Since the valuation is at most exponential in the size of the grammar, this gives rise to a (single) exponential running time. Previously only a double-exponential algorithm was known. As an application, we provide a conversion from context-free session types to simple grammars whose valuation is linear in the size of the type. In this way, we provide the first polynomial-time algorithm for deciding context-free session type equivalence.

Nuno Burnay, Antónia Lopes, Vasco T. Vasconcelos

Consumption of REST services has become a popular means of invoking code provided by third parties, particularly in web applications. Nowadays programmers of web applications can choose TypeScript over JavaScript to benefit from static type checking that enables validating calls to local functions or to those provided by libraries. Errors in calls to REST services, however, can only be found at run-time. In this paper, we present SafeRESTScript (SRS, for short) a language that extends the support of static analysis to calls to REST services, with the ability to statically find common errors such as missing or invalid data in REST calls and misuse of the results from such calls. SafeRESTScript features a syntax similar to JavaScript and is equipped with (i) a rich collection of types (including objects, arrays and refinement types)and (ii) primitives to natively support REST calls that are statically validated against specifications of the corresponding APIs. Specifications are written in HeadREST, a language that also features refinement types and supports the description of semantic aspects of REST APIs in a style reminiscent of Hoare triples. We present SafeRESTScript and its validation system, based on a general-purpose verification tool (Boogie). The evaluation of SafeRESTScript and of the prototype implementations for its validator, available in the form of an Eclipse plugin, is also discussed.

Vasco T. Vasconcelos, Philipp Haller

PLACES 2017 (full title: Programming Language Approaches to Concurrency- and Communication-cEntric Software) is the tenth edition of the PLACES workshop series. After the first PLACES, which was affiliated to DisCoTec in 2008, the workshop has been part of ETAPS every year since 2009 and is now an established part of the ETAPS satellite events. PLACES 2017 was held on 29th April in Uppsala, Sweden. The workshop series was started in order to promote the application of novel programming language ideas to the increasingly important problem of developing software for systems in which concurrency and communication are intrinsic aspects. This includes software for both multi-core systems and large-scale distributed and/or service-oriented systems. The scope of PLACES includes new programming language features, whole new programming language designs, new type systems, new semantic approaches, new program analysis techniques, and new implementation mechanisms. This volume consists of the papers accepted for presentation at the workshop.