Francisco Ortin

Dynamic adaptation of application aspects

In todays fast changing environments, adaptability has become an important feature in modern computing systems, programming languages and software engineering methods. Different approaches and techniques are used to achieve the development of adaptable systems. Following the principle of separation of concerns, aspect-oriented programming (AOP) distinguishes application functional code from specific concerns that cut across the system, creating the final application by weaving the programs main code and its specific aspects. In many cases, dynamic application adaptation is needed, but few existing AOP tools offer it in a limited way. Moreover, these tools use a fixed programming language: aspects cannot be implemented regardless of its programming language.We identify reflection as a mechanism capable of overcoming the deficiencies previously mentioned. We have developed a nonrestrictive reflective technique that achieves a real computational-environment jump, making every application and language feature adaptable at runtime--without any previously defined restriction. Moreover, our reflective platform is independent of the language selected by the programmer. Using the reflective capabilities of the platform presented, an AOP framework that achieves dynamic aspect weaving in a language-independent way has been constructed, overcoming the common limitations of existing AOP tools.

Efficient virtual machine support of runtime structural reflection

Increasing trends towards adaptive, distributed, generative and pervasive software have made object-oriented dynamically typed languages become increasingly popular. These languages offer dynamic software evolution by means of reflection, facilitating the development of dynamic systems. Unfortunately, this dynamism commonly imposes a runtime performance penalty. In this paper, we describe how to extend a production JIT-compiler virtual machine to support runtime object-oriented structural reflection offered by many dynamic languages. Our approach improves runtime performance of dynamic languages running on statically typed virtual machines. At the same time, existing statically typed languages are still supported by the virtual machine. We have extended the .Net platform with runtime structural reflection adding prototype-based object-oriented semantics to the statically typed class-based model of .Net, supporting both kinds of programming languages. The assessment of runtime performance and memory consumption has revealed that a direct support of structural reflection in a production JIT-based virtual machine designed for statically typed languages provides a significant performance improvement for dynamically typed languages.

Including both static and dynamic typing in the same programming language

Dynamic languages are becoming increasingly popular for different software development scenarios such as Web engineering, rapid prototyping or the construction of applications that require runtime adaptiveness. These languages are built on the idea of supporting reasoning about (and customising) program structure, behaviour and environment at runtime. The dynamism offered by dynamic languages is, however, counteracted by two main limitations: no early type error detection and fewer opportunities for compiler optimisations. To obtain the benefits of both dynamically and statically typed languages, the authors have designed the StaDyn programming language that provides both approaches. StaDyn keeps gathering-type information at compile time, even when dynamic variables are used. This type information is used to offer early type error detection, direct interoperation between static and dynamic codes and better runtime performance. Following the Separation of Concerns principle, it is possible to customise the trade-off between runtime flexibility of dynamic typing and safety, performance and robustness of static typing. A runtime performance assessment is presented to show an estimate of the benefits of combining dynamic and static typing in the same programming language.

Separating adaptable persistence attributes through computational reflection

To receive persistence capabilities, applications usually must explicitly access database management systems, such as object-oriented databases or object-relational mapping products. The usual way of building an application is tangling its functional code with explicit structured query language (SQL) or object query language (OQL) persistence statements. This tangling has several drawbacks: deficiencies in source code legibility, maintainability, and portability; lack of persistence functionality reuse; and low adaptability of persistence attributes. Separating crosscutting concerns such as persistence from the main application code can reduce software complexity and facilitate concerns reuse. A prototype persistence system shows how to use computational reflection to completely separate and adapt application persistence attribute at runtime.

OPTIMIZING REFLECTIVE PRIMITIVES OF DYNAMIC LANGUAGES

Dynamic languages are becoming widely used in software engineering due to the flexibility needs of specific software systems. Different example scenarios are the development of dynamic aspect oriented software, Web applications, adaptable and adaptive software or application frameworks. One important lack of these languages is compile-time error detection offered by static languages. However, runtime performance is the most serious limitation to use them in commercial software development. Although JIT optimizing compilation is a widely used technique to speed up intermediate code execution, this has not been successfully applied to dynamically adaptive platforms yet. We present an approach to improve the structural reflective primitives offered by dynamic languages. Looking for a language-neutral platform with a good JIT-based runtime performance, we have used the Microsoft shared source implementation of the CLI. Its model has been extended with semantics of prototype-based object-oriented models, much more suitable than the class-based one for reflective environments. This augmented semantics together with JIT generation of native code has produced significantly better runtime performance than the existing implementations.

Union and intersection types to support both dynamic and static typing

Although static typing provides undeniable benefits for the development of applications, dynamically typed languages have become increasingly popular for specific scenarios. Since each approach offers different benefits, the StaDyn programming language has been designed to support both dynamic and static typing. This paper describes the minimal core of the StaDyn programming language. Its type system performs type reconstruction over both dynamic and static implicitly typed references. A new interpretation of union and intersection types allows statically gathering the type information of dynamic references, which improves runtime performance and robustness. The evaluation of the generated code has shown how our approach offers an important runtime performance benefit.

Design Patterns for Teaching Type Checking in a Compiler Construction Course

A course in compiler construction seeks to develop an understanding of well-defined fundamental theory and typically involves the production of a language processor. In a graduate degree in software engineering, the development of a compiler contributes significantly to the developers comprehension of the practical application of theoretical concepts. Different formal notations are commonly used to define type systems, and some of them are used to teach the semantic analysis phase of language processing. In the traditional approach, attribute grammars are probably the most widely used ones. This paper shows how object-oriented design patterns represented in unified modeling language (UML) can be used to both teach type systems and develop the semantic analysis phase of a compiler. The main benefit of this approach is two-fold: better comprehension of theoretical concepts because of the use of notations known by the students (UML diagrams), and improvement of software engineering skills for the development of a complete language processor.

The Runtime Performance of invokedynamic: An Evaluation with a Java Library

The Java 7 platform includes the invokedynamic opcode in its virtual machine, a feature that lets programmers define-and dynamically change-the linkage of method call sites, thereby maintaining platform optimizations. A comprehensive evaluation of a new librarys performance includes a description of how to optimize real Java applications.

DIMAG: a framework for automatic generation of mobile applications for multiple platforms

Device Independence is a concept based on the idea of making services, applications and contents available to users regardless of the device used to enjoy them. One of the problems for developers of mobile applications is the number of different mobile platforms in the market. Therefore, a software platform to generate an application for as many platforms as possible would increase enormously the number of potential users. We propose a framework (DIMAG: Device Independent Mobile Application Generation framework) to generate mobile applications for multiple software platforms by means of a declarative description of the application. Besides, the generation of an application with this framework takes into account additional requirements like the need of mobile applications to consume and provide data from and to remote machines, or the dynamic load of the classes for code generation for a given mobile platform after identification of the device demanding a copy of the application. The generation of two simple but exemplifying applications shows the feasibility of DIMAG as a framework to relieve the problem of device fragmentation for mobile developers.

Non-restrictive computational reflection

Adaptable software systems and architectures give the programmer the ability to create applications that might customize themselves to runtime-emerging requirements. Computational reflection is a programming language technique that is commonly used to achieve the development of this kind of systems. Most runtime reflective systems use Meta-Object Protocols (MOPs). However, MOPs restrict the amount of features an application can customize, and the way they can express its own adaptation. Furthermore, this kind of systems uses a fixed programming language: they develop an interpreter, not a whole language-independent platform.What we present in this paper a non-restrictive reflective platform, called nitrO, that achieves a real computational-environment jump, making every application and language feature adaptable at runtime--without any previously defined restriction. Moreover, the platform has been built using a generic interpreter, in which the reflection mechanism is independent of the language selected by the programmer. Different applications may dynamically adapt each other, regardless of the programming language they use.