Hybrid Session Verification through Endpoint API Generation

© Springer-Verlag Berlin Heidelberg 2016.This paper proposes a new hybrid session verification methodology for applying session types directly to mainstream languages, based on generating protocol-specific endpoint APIs from multiparty session types. The API generation promotes static type checking of the behavioural aspect of the source protocol by mapping the state space of an endpoint in the protocol to a family of channel types in the target language. This is supplemented by very light run-time checks in the generated API that enforce a linear usage discipline on instances of the channel types. The resulting hybrid verification guarantees the absence of protocol violation errors during the execution of the session. We implement our methodology for Java as an extension to the Scribble framework, and use it to specify and implement compliant clients and servers for real-world protocols such as HTTP and SMTP

Formal Language Recognition with the Java Type Checker

This paper is a theoretical study of a practical problem: the automatic generation of Java Fluent APIs from their specification. We explain why the problem\u27s core lies with the expressive power of Java generics. Our main result is that automatic generation is possible whenever the specification is an instance of the set of deterministic context-free languages, a set which contains most "practical" languages. Other contributions include a collection of techniques and idioms of the limited meta-programming possible with Java generics, and an empirical measurement demonstrating that the runtime of the "javac" compiler of Java may be exponential in the program\u27s length, even for programs composed of a handful of lines and which do not rely on overly complex use of generics

Fling - A Fluent API Generator

We present the first general and practical solution of the fluent API problem - an algorithm, that given a deterministic language (equivalently, LR(k), k >= 0 language) encodes it in an unbounded parametric polymorphism type system employing only a polynomial number of types. The theoretical result is accompanied by an actual tool Fling - a fluent API compiler-compiler in the venue of YACC, tailored for embedding DSLs in Java

Session Kotlin: A hybrid session type embedding in Kotlin

Concurrency and distribution have become essential for building modern applications. However, developing and maintaining these apps is not an easy task. Communication errors are a common source of problems: unexpected messages cause runtime errors, and mutual dependencies lead to deadlocks. To address these issues, developers can define communication protocols that detail the structure and order of the transmitted messages, but maintaining protocol fidelity can be complex if carried out manually. Session types formalize this concept by materializing the communication protocol as a type that can be enforced by the language’s type system. In this thesis we present the first embedding of session types in Kotlin: we propose a Domain-Specific Language (DSL) for multiparty ses- sion types that lets developers write safe concurrent applications, with built-in validation and integrating code generation in the language’s framework.A concorrência e a distribuição têm-se tornado essenciais na construção de aplicações modernas. No entanto, desenvolver e manter estas aplicações não é tarefa fácil. Erros de comunicação são uma fonte comum de problemas: mensagens inesperadas causam erros durante a execução de código, e dependências mútuas levam a deadlocks. Para resolver estas questões, é tipico definir protocolos de comunicação que detalham a estrutura e a ordem das mensagens transmitidas, mas garantir o seu cumprimento pode ser complexo se feito manualmente. Os tipos de sessão formalizam este conceito ao materializar o protocolo de comunicação como um tipo que pode ser gerido pelo sistema de tipos da linguagem. Nesta tese apresentamos o primeiro embedding de tipos de sessão em Kotlin: propomos uma Linguagem de Domínio Específica para tipos de sessão com múltiplos participantes que permite aos programadores a escrita de aplicações concorrentes seguras, incorporando validação e integrando a geração de código no framework da linguagem

Fluent APIs in Functional Languages (full version)

Fluent API is an object-oriented pattern for smart and elegant embedded DSLs. As fluent API designs typically rely on function overloading, they are hard to realize in functional programming languages. We show how to write functional fluent APIs using parametric polymorphism and unification instead of overloading. Our designs support all regular and deterministic context-free DSLs and beyond

Microservice chatbot architecture for chronic patient support

Chatbots are able to provide support to patients suffering from very different conditions. Patients with chronic diseases or comorbidities could benefit the most from chatbots which can keep track of their condition, provide specific information, encourage adherence to medication, etc. To perform these functions, chatbots need a suitable underlying software architecture. In this paper, we introduce a chatbot architecture for chronic patient support grounded on three pillars: scalability by means of microservices, standard data sharing models through HL7 FHIR and standard conversation modeling using AIML. We also propose an innovative automation mechanism to convert FHIR resources into AIML files, thus facilitating the interaction and data gathering of medical and personal information that ends up in patient health records. To align the way people interact with each other using messaging platforms with the chatbot architecture, we propose these very same channels for the chatbot-patient interaction, paying special attention to security and privacy issues. Finally, we present a monitored-data study performed in different chronic diseases, and we present a prototype implementation tailored for one specific chronic disease, psoriasis, showing how this new architecture allows the change, the addition or the improvement of different parts of the chatbot in a dynamic and flexible way, providing a substantial improvement in the development of chatbots used as virtual assistants for chronic patients

On designing safe and flexible embedded DSLs with Java 5

AbstractAlthough embedded DSLs are widely used in both functional and dynamic languages they are yet to be widely accepted in the Java community. The best available examples are projects like jMock and Hibernate Criteria Query. In this paper we introduce the design of three novel practical embedded DSLs that we designed to showcase the power of Java language and specifically the changes introduced in Java 5. One of those DSLs is fully implemented as an open source project and is gathering momentum in the community. We proceed to discuss the approaches that allow designing safe and flexible DSLs by extracting generic patterns where possible and describing more specific idioms where necessary. It is our goal that this paper would serve as a starting point for someone designing an embedded DSL that takes full advantage of the Java 5 features