Symbol–Relation Grammars: A Formalism for Graphical Languages

AbstractA common approach to the formal description of pictorial and visual languages makes use of formal grammars and rewriting mechanisms. The present paper is concerned with the formalism of Symbol–Relation Grammars (SR grammars, for short). Each sentence in an SR language is composed of a set of symbol occurrences representing visual elementary objects, which are related through a set of binary relational items. The main feature of SR grammars is the uniform way they use context-free productions to rewrite symbol occurrences as well as relation items. The clearness and uniformity of the derivation process for SR grammars allow the extension of well-established techniques of syntactic and semantic analysis to the case of SR grammars. The paper provides an accurate analysis of the derivation mechanism and the expressive power of the SR formalism. This is necessary to fully exploit the capabilities of the model. The most meaningful features of SR grammars as well as their generative power are compared with those of well-known graph grammar families. In spite of their structural simplicity, variations of SR grammars have a generative power comparable with that of expressive classes of graph grammars, such as the edNCE and the N-edNCE classes

Propuesta de diseño modular para la configuración de un entorno virtual de eseñanza-aprendizaje con tutoría inteligente. Prototipo DECANO

456 páginas. Doctorado en Diseño.Un Entorno Virtual de Enseñanza-Aprendizaje con Tutoría Inteligente es un sistema que busca que la enseñanza se pueda adaptar a las características de cada estudiante y para su desarrollo, debe contar con muchos atributos como la reutilización, modificabilidad y adaptabilidad, elementos que hoy día se persiguen al diseñarlos. La gran mayoría de este tipo sistemas se construyen desde cero, puesto que no es posible reutilizar los elementos o modificar componentes, sin afectar su funcionalidad, lo que supone un gran esfuerzo en costos y tiempo. Esta tesis presenta el proceso para el diseño y construcción de un prototipo adaptable y modificable, considerando para ello una arquitectura modular, que toma en cuenta la instrucción individualizada, así como la integración del ambiente virtual colaborativo. Adicionalmente, plantea el modelo de interfaz gráfica diseñado a a partir de dimensiones sintático-simbólicas, para la traducción de sus componentes y funciones. Se ha desarrollado un modelo sistmático a partir de estos dos aspectos: interfaz y arquitectura, definiendo una metodología para el diseño, construcción y desarrollo, basada en las cualidades mencionadas, como principal aportación. También, se presenta el marco de trabajo para la construcción de prototipos similares por usuarios no especializados, de modo que se complemente con el uso y aplicación de programas y herramientas externas con la posibilidad de ser aplicado a diversos dominios

Conceptual modelling: A psychological perspective.

This thesis describes the formulation and experimental use of psychological principles that apply to conceptual modelling as practised during information systems development. The principles address cognition (perception, memory and mental models) and group dynamics. The aim is to determine whether application of fundamental psychological principles can help to make modellers, especially those who are relatively inexperienced, more effective. An experimental graphical modelling technique (method 'X') is presented that conforms to the psychological principles, together with a supporting software tool for visual construction of models in the design of typical business database systems. The effectiveness of both inexperienced and expert modellers using method 'X' in real business situations was compared with that of modellers using conventional object modelling. Data was gathered in a series of field experiments using participant observation, questionnaires, and interviews and by analysing the resulting models. With conventional object modelling, untrained modellers produced results that were grossly incomplete and incorrect (22-35%, on average). Using method 'X', untrained modellers produced models that were almost complete and correct (better than 82%). Significant productivity gains were observed with method 'X' (approximately 150% for expert modeller and over 450% for untrained modellers). For an expert modeller no measurable differences in quality were observed between methods, but the modeller regarded the quality of method 'X' models as better and expressed a preference method 'X' over the conventional approach. The results appear to support the idea of re-engineering conceptual modelling practice according to psychological first principles. The fact that more dramatic performance improvements were observed for inexperienced modellers suggests that modelling need not require a high degree of expertise, if methods and tools are adapted appropriately. The results could be exploited to empower untrained modellers, such as end users, who wish to develop large software systems but lack access to the skills of trained IT professionals