Papers by Jesus García Molina
arXiv (Cornell University), May 23, 2022
Schema evolution is a crucial aspect in database management. The proposed taxonomies of schema ch... more Schema evolution is a crucial aspect in database management. The proposed taxonomies of schema changes have neglected the set of operations that involves relationships between entity types: aggregation and references, as well as the possible existence of structural variations for schema types, as most of NoSQL systems are schemaless. The distinction between entity types and relationship types, which is typical of graph schemas, is also not taken into account in the published works. Moreover, NoSQL schema evolution poses the challenge of having different data models, and no standard specification exists for them. In this paper, a generic approach for evolving NoSQL and relational schemas is presented, which is based on the U-Schema unified data model that includes aggregation and reference relationships, and structural variations. For this data model, we introduce a taxonomy of schema changes for all the U-Schema elements, which is implemented by creating the Orion database-independent language. We will show how Orion can be used to automatically generate evolution scripts for a set of NoSQL databases, and the feasibility of each schema operation will be analyzed through the performance results obtained. The taxonomy has been formally validated by means of Alloy, and two case studies show the application of Orion. Keywords NoSQL databases • Schema evolution • Evolution management • Taxonomy of changes • Schema change operations * This work has been funded by the Spanish Ministry of Science, Innovation and Universities (project grant PID2020-117391GB-I00). † Formatted for arXiv.org.
Jornadas de Ingeniería del Software y Bases de Datos, 1996
En este trabajo presentamos el modelo de vistas definido para el modelo de datos orientado a obje... more En este trabajo presentamos el modelo de vistas definido para el modelo de datos orientado a objetos Chimera, comparándolo con las propuestas más relevantes de mecanismos de vistas orientadas a objetos. La comparación se organiza en tres dimensiones: i) el posicionamiento de una vista en el esquema existente, ii) la naturaleza de la extensión de una vista y iii) las
Companion Proceedings of the 2023 ACM SIGCHI Symposium on Engineering Interactive Computing Systems
We demonstrate Guizmo, a model-driven engineering framework aimed at generating final graphical u... more We demonstrate Guizmo, a model-driven engineering framework aimed at generating final graphical user interfaces from wireframes according to the following process: (1) design a concrete user interface in a wireframe tool, (2) export/import the wireframe definition into Guizmo for generation of a wireframe model, (3) for segmenting the wireframe into regions by region detection, (4) for inferring positions and dimensions of individual interface elements, (5) in order to obtain a complete layout model that is used for generating the code of a final user interface by model-to-code generation. CCS CONCEPTS • Software and its engineering → Graphical user interface languages; System modeling languages; Source code generation; Model-driven software engineering; • Computing methodologies → Image segmentation; • Human-centered computing → Interaction design process and methods.
arXiv (Cornell University), Apr 13, 2022
Most NoSQL systems are schema-on-read: data can be stored without first having to declare a schem... more Most NoSQL systems are schema-on-read: data can be stored without first having to declare a schema that imposes a structure. This schemaless feature offers flexibility to evolve data-intensive applications when data frequently change. However, freeing from declaring schemas does not mean their absence, but rather that they are implicit in data and code. Therefore, diagramming tools similar to those available for relational systems are also needed to help developers and administrators designing and understanding NoSQL schemas. Visualizing diagrams is not practical if schemas contain hundreds of database entities, and exploration or query facilities are then needed. In schemaless NoSQL stores, data of the same entity can be stored with different structure (e.g., non-uniform types and optional fields), which can increase the difficulty of having readable diagrams. NoSQL schema management tools should therefore have three main components: schema extraction, schema visualization, and schema query. Since that there exists four main NoSQL data models, it is convenient that such tools can be built on a generic data model so that they provide platformindependence (of data models and data stores) to query and visualize schemas. With the aim of favoring the creation of generic database tools, the authors of this paper defined the U-Schema unified data model that integrates the four main NoSQL data models as well as the relational model. This paper is focused on querying NoSQL and relational schemas which are represented as U-Schema models. We present the SkiQL language designed on U-Schema to achieve a platform-independent schema query service. SkiQL provides two constructs: schema-query and relationship-query. The former allows to obtain information of entity or relationship types, and the latter that of the aggregations or references (relations among types). We will show how SkiQL was evaluated by calculating well-known metrics for languages as well as using a survey with developers with experience in NoSQL.
The application of Model-Driven Development (MDD) techniques in the area of software modernizatio... more The application of Model-Driven Development (MDD) techniques in the area of software modernization is an emerging discipline where methods, tools and techniques have to be still devised. The activities involved in a software modernization process can be described in the context of the horseshoe model [1]. Figure 1 shows the horseshoe model adapted to the application of MDD and the three main processes involved. A reverse engineering process is first applied to obtain models that are high-level abstractions of the information of the source software system artefacts. The restructuring process is then in charge of converting the obtained models into other models which represent the redesigned system conforming to the target architecture. Finally, the forward engineering process generates the target software system artefacts.
Electron. Commun. Eur. Assoc. Softw. Sci. Technol., 2010
Context awareness refers to systems that can both sense and react based on their environment. The... more Context awareness refers to systems that can both sense and react based on their environment. The complexity of these systems makes necessary to apply software engineering techniques in their development, such as Model-Driven Software development (MDD). One of the main difficulties that developers of context-aware systems must tackle is how to manage the needed context information. In this paper, we present MLContext, a textual Domain Specific Language (DSL) which is specially tailored for modeling context information and automatically generating software artefacts from context models. It has been designed to provide a high-level abstraction, to be an easy to learn, and to promote reuse of context models. We have built a toolkit including an editor and a parser to convert MLContext textual specifications into models. As a proof of concept, we have automatically generated ontologies and Java code for the OCP middleware. MLContext models can be reused in applications with the same con...
Information Systems, 2021
The Database field is undergoing significant changes. Although relational systems are still predo... more The Database field is undergoing significant changes. Although relational systems are still predominant, the interest in NoSQL systems is continuously increasing. In this scenario, polyglot persistence is envisioned as the database architecture to be prevalent in the future. Therefore, database tools and systems are evolving to support several data models. Multi-model database tools normally use a generic or unified metamodel to represent schemas of the data model that they support. Such metamodels facilitate developing database utilities, as they can be built on a common representation. Also, the number of mappings required to migrate databases from a data model to another is reduced, and integrability is favored. In this paper, we present the U-Schema unified metamodel able to represent logical schemas for the four most popular NoSQL paradigms (columnar, document, key-value, and graph) as well as relational schemas. We will formally define the mappings between U-Schema and the data model defined for each database paradigm. How these mappings have been implemented and validated will be discussed, and some applications of U-Schema will be shown. To achieve flexibility to respond to data changes, most of NoSQL systems are "schema-on-write," and the declaration of schemas is not required. Such an absence of schema declaration makes structural variability possible, i.e., stored data of the same entity type can have different structure. Moreover, data relationships supported by each data model are different; For example, document stores have aggregate objects but not relationship types, whereas graph stores offer the opposite. Through the paper, we will show how all these issues have been tackled in our approach. As far as we know, no proposal exists in the literature of a unified metamodel for relational and the NoSQL paradigms which describes how each individual data model is integrated and mapped. Our metamodel goes beyond the existing proposals by distinguishing entity types and relationship types, representing aggregation and reference relationships, and including the notion of structural variability. Our contributions also include developing schema extraction strategies for schemaless systems of each NoSQL data model, and tackling performance and scalability in the implementation for each store.
CLEI Electronic Journal, 2018
This issue of the CLEIej consists of three main parts: i) a review paper on the state of the art ... more This issue of the CLEIej consists of three main parts: i) a review paper on the state of the art of how contextual information extracted from a user task can help to improve searches for contents relevant to this task; ii) extended and revised versions of Selected Papers (which correspond to the second and third best paper from each track) presented at the XX Ibero-American Conference on Software Engineering (CIbSE 2017), which took place in Buenos Aires, Argentina, in May 2017; and, iii) extended and revised versions of selected papers from LACLO 2016, the XI Latin American Conference on Learning Objects and Technology, which took place in San José, Costa Rica, in October 2016.
Revista de Educación a Distancia (RED), 2016
Resumen Las universidades se enfrentan al reto de producir contenidos online interactivos para se... more Resumen Las universidades se enfrentan al reto de producir contenidos online interactivos para ser utilizados en cursos de los estudios reglados o como cursos masivos online (MOOC). La producción de estos contenidos requiere actualmente un gran esfuerzo de los docentes que deben dedicar una gran cantidad de tiempo. Por ello, las universidades deberán proporcionar recursos (herramientas, métodos, personal,..) que faciliten esta tarea a los docentes. En este sentido,
Advances in Intelligent and Soft Computing, 2011
Developing reliable context-aware applications remains a big challenge, even after a decade of re... more Developing reliable context-aware applications remains a big challenge, even after a decade of research in this area. Usually a lot of code is required to handle an application's correct behavior in a variety of different situations. Along with a growing amount of code, also increases the risk of programming errors that may lead to an undesired behavior in particular situations. In this paper we present a domain specific language (DSL) for developing context-aware applications. It allows creating context quality models which are transformed into software artifacts of the final application. This code generation saves time and effort, and helps to ensure an appropriate autonomic behavior at runtime in inherently uncertain situations.
Concepts, Methodologies, Tools, and Applications
Domain Specific Languages (DSL) are becoming increasingly more important with the emergence of Mo... more Domain Specific Languages (DSL) are becoming increasingly more important with the emergence of Model-Driven paradigms. Most literature on DSLs is focused on describing particular languages, and there is still a lack of works that compare different approaches or carry out empirical studies regarding the construction or usage of DSLs. Several design choices must be made when building a DSL, but one important question is whether the DSL will be external or internal, since this affects the other aspects of the language. This chapter aims to provide developers confronting the internal-external dichotomy with guidance, through a comparison of the RubyTL and Gra2MoL model transformations languages, which have been built as an internal DSL and an external DSL, respectively. Both languages will first be introduced, and certain implementation issues will be discussed. The two languages will then be compared, and the advantages and disadvantages of each approach will be shown. Finally, some of the lessons learned will be presented. Concrete syntax: The notation that the users of a language are provided with in order to develop programs or specifications.
Model-driven engineering (MDE) can be used both to create new software systems and to evolve or m... more Model-driven engineering (MDE) can be used both to create new software systems and to evolve or modernize existing software systems. In model-driven software evolution, models are extracted from the system and then MDE techniques are applied to make it evolve. Most evolution scenarios involve dealing with existing source code written in some programming languages. Therefore, a bridge from grammarware to MDE must be built to extract models from such a source code. In this paper we present an approach for the extraction of models conforming to a target metamodel from source code conforming to the grammar of a programming language. This approach is based on the definition of a grammar-to-model transformation language, named Gra2MoL, which is a language specially tailored to address the grammarware-modelware bridge in modernization scenarios. The language promotes grammar reuse, and provides domain-specific features such as a powerful query language to traverse syntax trees.
Theory and Practice of Object Systems, 1997
In the context of object-oriented programming languages we propose an extension of the Smalltalk ... more In the context of object-oriented programming languages we propose an extension of the Smalltalk environment which provides for the possibility of constructing software by applying the Design by Contract methodology, introduced by Meyer as a way of developing reliable software. In this sense, both correctness and robustness are increased by using the mechanisms incorporated to Smalltalk as a consequence of the proposed extension. Thus, assertions are used to guarantee the preconditions and postconditions of methods and ...
In this paper, we describe the current state of a project whose aim is the extension of the Small... more In this paper, we describe the current state of a project whose aim is the extension of the Smalltalk environment by incorporating mechanisms and tools promoting the development of quality software. We have included in the Smalltalk context a number of possibilities, which were not available in the original definition of the language. In this sense, assertions can be specified in our extension, in an Eiffellike style, so gaining all benefits that the use of assertions bring with them. We also propose an approach to declare private ...
Tecnica Administrativa, 2007
ABSTRACT En este trabajo se presenta una estrategia para obtener de modo sistemático el modelo de... more ABSTRACT En este trabajo se presenta una estrategia para obtener de modo sistemático el modelo de casos de uso y el modelo conceptual, a partir del modelado del negocio basado en diagramas de actividades UML. Después de determinar los procesos del negocio de la organización bajo estudio, y de describir sus flujos de trabajo mediante diagramas de actividad, los casos de uso son identificados y estructurados a partir de las actividades de cada proceso, mientras que los conceptos que aparecen en el modelo conceptual se obtienen a partir de los datos que fluyen entre las actividades. Además, las reglas del negocio son identificadas e incluidas en un glosario, como parte de la especificación de datos y actividades. Un aspecto destacable de nuestra propuesta es el hecho deque el modelado conceptual y el de casos de uso se realiza en paralelo, haciendo más fácil la identificación y especificación de casos de uso adecuados. Tanto el modelado de casos de uso como el modelado conceptual forman parte de la fase de análisis de requisitos de un modelo de proceso completo en cuya definición estamos trabajando. Este proceso está siendo experimentando en un organismo de tamaño medio de la Administración Autonómica. A guide to requirements modeling is presented in this paper, in which use cases and the conceptual model are directly obtained from a business modeling based on UML activity diagrams. After determining the business processes of the organization, and describing their workflows by means of activity diagrams, use cases are elicited and structured starting from the activities of each process, while the concepts of the conceptual model are obtained from the data that flow between activities. Furthermore, business rules are identified and included in a glossary, as part of the data and activities specification. One notable aspect of our proposal is that use case and conceptual modeling are performed at the same time, thus making the identification and specification of suitable usecases easier. Both use case and conceptual modeling belong to the requirements analysis phase, which is part of a complete process model on whose definition we are currently working. This process is being experimented in a medium sized organism of a Regional Public Administration.
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Papers by Jesus García Molina