Do RESTful API Design Rules Have an Impact on the Understandability of Web APIs? A Web-Based Experiment with API Descriptions

Context: Web APIs are one of the most used ways to expose application functionality on the Web, and their understandability is important for efficiently using the provided resources. While many API design rules exist, empirical evidence for the effectiveness of most rules is lacking. Objective: We therefore wanted to study 1) the impact of RESTful API design rules on understandability, 2) if rule violations are also perceived as more difficult to understand, and 3) if demographic attributes like REST-related experience have an influence on this. Method: We conducted a controlled Web-based experiment with 105 participants, from both industry and academia and with different levels of experience. Based on a hybrid between a crossover and a between-subjects design, we studied 12 design rules using API snippets in two complementary versions: one that adhered to a "rule" and one that was a "violation" of this rule. Participants answered comprehension questions and rated the perceived difficulty. Results: For 11 of the 12 rules, we found that "violation" performed significantly worse than "rule" for the comprehension tasks. Regarding the subjective ratings, we found significant differences for 9 of the 12 rules, meaning that most violations were subjectively rated as more difficult to understand. Demographics played no role in the comprehension performance for "violation". Conclusions: Our results provide first empirical evidence for the importance of following design rules to improve the understandability of Web APIs, which is important for researchers, practitioners, and educators.Comment: Currently under review at Empirical Software Engineering (EMSE

Desarrollo automatizado de sistemas teleo-reactivos a partir de objetivos: un enfoque basado en componentes y dirigido por modelos

[SPA] Esta tesis doctoral se presenta bajo la modalidad de compendio de publicaciones. Está formada por un total de cuatro artículos publicados en revistas del segundo cuartil del Journal Citation Reports. El artículo “A systematic literature review of the Teleo-Reactive paradigm” ofrece una completa revisión sistemática de la literatura existente sobre el paradigma Teleo-Reactivo desde su presentación por el profesor Nils Nilsson en el año 1994. Su papel en esta tesis es el de servir de estado del arte de dicho paradigma, ofreciendo una buena perspectiva de la evolución de los sistemas Teleo-Reactivos desde su formulación hasta el presente. Para poder desarrollar sistemas Teleo-Reactivos a partir de objetivos, surgió la necesidad de especificar los requisitos de estos sistemas usando el lenguaje más apropiado. Ese es uno de los objetivos principales del artículo “A controlled experiment to evaluate the understandability of KAOS and i* for modeling Teleo-Reactive systems”. Como resultado de dicho trabajo se decidió utilizar i* dado que el experimento realizado mostró que las especificaciones realizadas con dicho lenguaje resultaban ligeramente más comprensibles que las realizadas con KAOS. Aunque i* resultaba más comprensible a la hora de especificar requisitos para sistemas Teleo-Reactivos, también presentaba ciertas debilidades. Estas debilidades han sido descritas detalladamente en el artículo “A family of experiments to evaluate the understandability of TRiStar and i* for modeling Teleo-Reactive systems”, en el que además se propone una extensión al lenguaje que permite superarlas. La extensión propuesta se denomina TRiStar y fue inicialmente presentada en [Morales15]. TRiStar ha demostrado superar los problemas de comprensibilidad identificados en i* en el modelado de sistemas Teleo-Reactivos mediante una familia de experimentos realizada con estudiantes de últimos cursos de grado y con desarrolladores software experimentados, cuyos resultados se exponen exhaustivamente en el artículo mencionado. En él se describe, además, un mecanismo que permite obtener mediante transformación de modelos el programa Teleo-Reactivo equivalente a un diagrama TRiStar dado. TRiStar permite, por lo tanto, partiendo de los objetivos de un sistema Teleo-Reactivo obtener un diagrama que especifique su comportamiento. Ese diagrama puede ser transformado en un programa Teleo-Reactivo equivalente. Y siguiendo las transformaciones descritas en “From Teleo-Reactive specifications to architectural components: a model-driven approach” se puede obtener a partir del programa Teleo-Reactivo el modelo de componentes y la máquina de estados que describe el comportamiento de cada uno de esos componentes. Con estos elementos y usando un framework como el descrito en [Iborra09] se cerraría el proceso de desarrollo del sistema Teleo-Reactivo. Como resultado de las investigaciones realizadas en el transcurso de esta tesis, y aunque no forma parte del compendio, hay un quinto artículo [Sánchez16] que está en segunda revisión en el Journal of Systems and Software en el que se estudian las posibilidades de introducir requisitos de tiempo real cuando se sigue el enfoque Teleo-Reactivo desde el modelado a la implementación de un sistema. Tras realizar un estudio del tipo de restricciones temporales que se pueden imponer desde el punto de vista Teleo-Reactivo, se considera la posibilidad de utilizar TeleoR [Clark14] para incorporar dichas restricciones y se proponene una serie de extensiones a TRiStar para permitir representar requisitos temporales. Estas extensiones dan lugar a lo que hemos llamado TRiStar+. [ENG] This doctoral dissertation has been presented in the form of thesis by publication. It is comprised of four articles indexed in the second quartile of the Journal Citation Reports. The article “A systematic literature review of the Teleo-Reactive paradigm” offers a complete systematic review of the existing literature on the Teleo-Reactive paradigm since Prof. Nils Nilsson presented it in 1994. It plays the role of state of the art of that paradigm, showing a perspective of the evolution of Teleo-Reactive systems from their formulation to present time. In order to develop Teleo-Reactive systems starting from its goals, there is the need of specifying the requirements of these systems using the most adequate language. That is one of the main objectives of the article “A controlled experiment to evaluate the understandability of KAOS and i* for modeling Teleo-Reactive systems”. As a result, we decided to use i* because the experiment showed that i* specifications where slightly more understandable than those made using KAOS. Although i* was more understandable when specifying requirements for Teleo-Reactive systems, the experiment also showed some shortcomings. These shortcomings have been deeply described in the article “A family of experiments to evaluate the understandability of TRiStar and i* for modeling Teleo-Reactive systems”. In this article, an extension to i* is proposed in order to overcome the identified limitations. The proposed extension is named TRiStar and was initially presented at [Morales15]. TRiStar has shown to be more understandable than i* when modeling Teleo-Reactive systems through a family of experiments done with last year students and experienced software developers, whose results are described in the aforementioned article. In that article, a mechanism to obtain a Teleo-Reactive program starting from a TRiStar diagram is also described. Therefore, TRiStar allows obtaining a diagram which specifies the behavior of a Teleo-Reactive system starting from its goals. That diagram can be transformed into an equivalent Teleo-Reactive program. Then, following the transformations described in “From Teleo-Reactive specifications to architectural components: a model-driven approach”, a component model and the state machine describing the behavior of each of those components can be obtained. With these elements and using a framework as that described in [Iborra09], the development process of the Teleo-Reactive system would be finished. As a result of the research carried out during this dissertation there is another article, which is not comprised in the compilation, in second revision at the Journal of Systems and Software [Sánchez16]. In that article, after making a study of the type of timing constraints from the TR perspective, we consider the possibility of using TeleoR [Clark14] for incorporating such constraints. Some extensions on TRiStar notation are proposed to represent temporal requirements. Those extensions have been named TRiStar+.[ENG] This doctoral dissertation has been presented in the form of thesis by publication. It is comprised of four articles indexed in the second quartile of the Journal Citation Reports. The article “A systematic literature review of the Teleo-Reactive paradigm” offers a complete systematic review of the existing literature on the Teleo-Reactive paradigm since Prof. Nils Nilsson presented it in 1994. It plays the role of state of the art of that paradigm, showing a perspective of the evolution of Teleo-Reactive systems from their formulation to present time. In order to develop Teleo-Reactive systems starting from its goals, there is the need of specifying the requirements of these systems using the most adequate language. That is one of the main objectives of the article “A controlled experiment to evaluate the understandability of KAOS and i* for modeling Teleo-Reactive systems”. As a result, we decided to use i* because the experiment showed that i* specifications where slightly more understandable than those made using KAOS. Although i* was more understandable when specifying requirements for Teleo-Reactive systems, the experiment also showed some shortcomings. These shortcomings have been deeply described in the article “A family of experiments to evaluate the understandability of TRiStar and i* for modeling Teleo-Reactive systems”. In this article, an extension to i* is proposed in order to overcome the identified limitations. The proposed extension is named TRiStar and was initially presented at [Morales15]. TRiStar has shown to be more understandable than i* when modeling Teleo-Reactive systems through a family of experiments done with last year students and experienced software developers, whose results are described in the aforementioned article. In that article, a mechanism to obtain a Teleo-Reactive program starting from a TRiStar diagram is also described. Therefore, TRiStar allows obtaining a diagram which specifies the behavior of a Teleo-Reactive system starting from its goals. That diagram can be transformed into an equivalent Teleo-Reactive program. Then, following the transformations described in “From Teleo-Reactive specifications to architectural components: a model-driven approach”, a component model and the state machine describing the behavior of each of those components can be obtained. With these elements and using a framework as that described in [Iborra09], the development process of the Teleo-Reactive system would be finished. As a result of the research carried out during this dissertation there is another article, which is not comprised in the compilation, in second revision at the Journal of Systems and Software [Sánchez16]. In that article, after making a study of the type of timing constraints from the TR perspective, we consider the possibility of using TeleoR [Clark14] for incorporating such constraints. Some extensions on TRiStar notation are proposed to represent temporal requirements. Those extensions have been named TRiStar+.Universidad Politécnica de CartagenaPrograma Oficial de Doctorado en Tecnologías de la Información y Comunicacione

WHAT’S IN A SERVICE? SPECIFYING THE BUSINESS SEMANTICS OF SOFTWARE SERVICES

The success of the service-oriented computing (SOC) paradigm considerably depends on the ability of service consumers to distinguish between published services and choose the ones best suited for a development project. Current SOC standards primarily give information about technical service properties such as the programming interface and the binding information. This enables designers to analyze the technical compatibility of services with the rest of the system. On the basis of such technical information, it is difficult to assess which business semantics a service actually implements and whether it is suited to satisfy functional requirements, however. In this paper, we therefore propose the WS-Functionality language which allows providers to specify the business semantics of software services in business terms. In a design science approach, we firstly describe how conceptual models, which contain business terms and relationships between them, can be used to specify the business semantics of services. Building upon this solution concept, we present the language constructs of WS-Functionality and show a prototypic implementation as proof-of-concept. In a controlled experiment, we were able to support our claim that the information provided with WS-Functionality enhances the ability of service consumers to analyze the business semantics of services and judge whether it satisfies existing functional requirements