UML Class Diagram or Entity Relationship Diagram : An Object Relational Impedance Mismatch

It is now nearly 30 years since Peter Chen’s watershed paper “The Entity-Relationship Model –towards a Unified View of Data”. [1] The entity relationship model and variations and extensions to ithave been taught in colleges and universities for many years. In his original paper Peter Chen looked at converting his new ER model to the then existing data structure diagrams for the Network model. In recent years there has been a tendency to use a Unified Modelling Language (UML) class diagram forconceptual modeling for relational databases, and several popular course text books use UMLnotation to some degree [2] [3]. However Object and Relational technology are based on different paradigms. In the paper we argue that the UML class diagram is more of a logical model (implementation specific). ER Diagrams on theother hand, are at a conceptual level of database design dealing with the main items and their relationships and not with implementation specific detail. UML focuses on OOAD (Object Oriented Analysis and Design) and is navigational and program dependent whereas the relational model is set based and exhibits data independence. The ER model provides a well-established set of mapping rules for mapping to a relational model. In this paper we look specifically at the areas which can cause problems for the novice databasedesigner due to this conceptual mismatch of two different paradigms. Firstly, transferring the mapping of a weak entity from an Entity Relationship model to UML and secondly the representation of structural constraints between objects. We look at the mixture of notations which students mistakenly use when modeling. This is often the result of different notations being used on different courses throughout their degree. Several of the popular text books at the moment use either a variation of ER,UML, or both for teaching database modeling. At the moment if a student picks up a text book they could be faced with either; one of the many ER variations, UML, UML and a variation of ER both covered separately, or UML and ER merged together. We regard this problem as a conceptual impedance mismatch. This problem is documented in [21] who have produced a catalogue of impedance mismatch problems between object-relational and relational paradigms. We regard the problems of using UML class diagrams for relational database design as a conceptual impedance mismatch as the Entity Relationship model does not have the structures in the model to deal with Object Oriented concepts Keywords: EERD, UML Class Diagram, Relational Database Design, Structural Constraints, relational and object database impedance mismatch. The ER model was originally put forward by Chen [1] and subsequently extensions have been added to add further semantics to the original model; mainly the concepts of specialisation, generalisation and aggregation. In this paper we refer to an Entity-Relationship model (ER) as the basic model and an extended or enhanced entity-relationship model (EER) as a model which includes the extra concepts. The ER and EER models are also often used to aid communication between the designer and the user at the requirements analysis stage. In this paper when we use the term “conceptual model” we mean a model that is not implementation specific.ISBN: 978-84-616-3847-5 3594Peer reviewe

The Use of UML Class Diagrams To Teach Database Modelling and Database Design

It is now nearly 30 years since Peter Chen’s watershed paper “The Entity-Relationship Model – towards a Unified View of Data”. [1] The entity relationship model and variations and extensions to it have been taught in colleges and universities for many years. In his original paper Peter Chen looked at converting his new ER model to the then existing data structure diagrams for the Network model. In recent years there has been a tendency to use a Unified Modelling Language (UML) class diagram for conceptual modelling for relational databases, and several popular course text books use UML notation to some degree [2] [3]. This paper looks at the usefulness of using UML class diagrams for teaching database design in undergraduate courses. In this paper we look specifically at two concepts which can cause problems for the novice database designer. Firstly transferring the concept of a weak entity from an Entity Relationship model to UML and secondly the notation for structural constraints in different diagramming notations. We also look at the mixture of notations which students mistakenly use when modelling. This is often the result of different notations being used on different courses throughout their degree. Peter Chen wrote in his original paper “The entity-relationship model can be used as a tool in the structured design of databases using the network model” today we could write “the UML class diagram can be used as a tool in the structured design of databases using the relational model”. Or can we

ARDI: automatic generation of RDFS models from heterogeneous data sources

The current wealth of information, typically known as Big Data, generates a large amount of available data for organisations. Data Integration provides foundations to query disparate data sources as if they were integrated into a single source. However, current data integration tools are far from being useful for most organisations due to the heterogeneous nature of data sources, which represents a challenge for current frameworks. To enable data integration of highly heterogeneous and disparate data sources, this paper proposes a method to extract the schema from semi-structured (such as JSON and XML) and structured (such as relational) data sources, and generate an equivalent RDFS representation. The output of our method complements current frameworks and reduces the manual workload required to represent the input data sources in terms of the integration canonical data model. Our approach consists of production rules at the meta-model level that guarantee the correctness of the model translations. Finally, a tool for implementing our approach has been developed.Peer ReviewedPostprint (author's final draft

Getting Relational Database from Legacy Data-MDRE Approach

The previous management information systems turning on traditional mainframe environment are often written in COBOL and store their data in files; they are usually large and complex and known as legacy systems. These legacy systems need to be maintained and evolved due to several causes, including correction of anomalies, requirements change, management rules change, new reorganization, etc. But, the maintenance of legacy systems becomes over years extremely complex and highly expensive, In this case, a new or an improved system must replace the previous one. However, replacing those systems completely from scratch is also very expensive and it represents a huge risk. Nevertheless, they should be evolved by profiting from the valuable knowledge embedded in them. This paper proposes a reverse engineering process based on Model Driven engineering that presents a solution to provide a normalized relational database which includes the integrity constraints extracted from legacy data. A CASE tool CETL: (COBOL Extract Transform Load) is developed to support the proposal. Keywords: legacy data, reverse engineering, model driven engineering, COBOL metamodel, domain class diagram, relational database

Understanding the Elements of Executable Architectures Through a Multi-Dimensional Analysis Framework

The objective of this dissertation study is to conduct a holistic investigation into the elements of executable architectures. Current research in the field of Executable Architectures has provided valuable solution-specific demonstrations and has also shown the value derived from such an endeavor. However, a common theory underlying their applications has been missing. This dissertation develops and explores a method for holistically developing an Executable Architecture Specification (EAS), i.e., a meta-model containing both semantic and syntactic information, using a conceptual framework for guiding data coding, analysis, and validation. Utilization of this method resulted in the description of the elements of executable architecture in terms of a set of nine information interrogatives: an executable architecture information ontology. Once the detail-rich EAS was constructed with this ontology, it became possible to define the potential elements of executable architecture through an intermediate level meta-model. The intermediate level meta-model was further refined into an interrogative level meta-model using only the nine information interrogatives, at a very high level of abstraction

A Model Driven Approach to Model Transformations

The OMG's Model Driven Architecture (MDA) initiative has been the focus of much attention in both academia and industry, due to its promise of more rapid and consistent software development through the increased use of models. In order for MDA to reach its full potential, the ability to manipulate and transform models { most obviously from the Platform Independent Model (PIM) to the Platform Specific Models (PSM) { is vital. Recognizing this need, the OMG issued a Request For Proposals (RFP) largely concerned with finding a suitable mechanism for trans- forming models. This paper outlines the relevant background material, summarizes the approach taken by the QVT-Partners (to whom the authors belong), presents a non-trivial example using the QVT-Partners approach, and finally sketches out what the future holds for model transformations

The Automated analysis of object-oriented designs

This thesis concerns the use of software measures to assess the quality of object-oriented designs. It examines the ways in which design assessment can be assisted by measurement and the areas in which it can't. Other work in software measurement looks at defining and validating measures,or building prediction systems. This work is distinctive in that it examines the use of measures to help improve design quality during design time. To evaluate a design based on measurement results requires a means of relating measurement values to particular design problems or quality levels. Design heuristics were used to make this connection between measurement and quality. A survey was carried out to find suggestions for guidelines, rules and heuristics from the 00 design literature. This survey resulted in a catalogue of 288 suggestions for 00 design heuristics. The catalogue was structured around the 00 constructs to which the heuristics relate, and includes information on various heuristic attributes. This scheme is intended to allow suitable heuristics to be quickly located and correctly applied. Automation requires tool support. A tool was built which augmented the functionality available in existing sets, and taking input from multiple sources of design information (e.g., CASE tools and source code) and the described so far presents a potential method for automated design assessment provides the means of automation. An empirical study was then required to consider the efficacy of the method and evaluate the novel features of the tool. A case study was used to explore the approach taken by, and evaluate the effectiveness of, 15 subjects using measures and heuristics to assess the design of a small 00 system(IS classes). This study showed that semantic heuristics tended to highlight significant problems, but where attempts were made to automate these it often led to false problems being identified. This result, along with a previous finding that around half of quality criteria are not automatically assessable at design time, strongly suggeststhat people are still a necessary part of design assessment. The main result of the case study was that the subjects correctly identified 90% of the major design problems and were very positive about their experience of using measurement to support design assessment

A Comparative Analysis of Graph Vs Relational Database For Instructional Module Development System

abstract: In today's data-driven world, every datum is connected to a large amount of data. Relational databases have been proving itself a pioneer in the field of data storage and manipulation since 1970s. But more recently they have been challenged by NoSQL graph databases in handling data models which have an inherent graphical representation. Graph databases with the ability to store physical relationships between two nodes and native graph processing technique have been doing exceptionally well in graph data storage and management for applications like recommendation engines, biological modeling, network modeling, social media applications, etc. Instructional Module Development System (IMODS) is a web-based software system that guides STEM instructors through the complex task of curriculum design, ensures tight alignment between various components of a course (i.e., learning objectives, content, assessments), and provides relevant information about research-based pedagogical and assessment strategies. The data model of IMODS is highly connected and has an inherent graphical representation between all its entities with numerous relationships between them. This thesis focuses on developing an algorithm to determine completeness of course design developed using IMODS. As part of this research objective, the study also analyzes the data model for best fit database to run these algorithms. As part of this thesis, two separate applications abstracting the data model of IMODS have been developed - one with Neo4j (graph database) and another with PostgreSQL (relational database). The research objectives of the thesis are as follows: (i) evaluate the performance of Neo4j and PostgreSQL in handling complex queries that will be fired throughout the life cycle of the course design process; (ii) devise an algorithm to determine the completeness of a course design developed using IMODS. This thesis presents the process of creating data model for PostgreSQL and converting it into a graph data model to be abstracted by Neo4j, creating SQL and CYPHER scripts for undertaking experiments on both platforms, testing and elaborate analysis of the results and evaluation of the databases in the context of IMODS.Dissertation/ThesisMasters Thesis Computer Science 201

Performance analysis of persistence technologies for cloud repositories of models

The growing adoption of Model Driven Development (MDD) in companies during last decade arises some model interchange problems. Companies need support to interchange models and reuse parts of them for developing new projects. Traditional tools for model edition and model interchange have different performance issues related to the models storage. There are mainly two styles to organize the persistence of models into repositories: a complex and large model or a large amount of small models. This last approach is common in companies that generate software from models. In this paper, we analyse performance properties of different persistence technologies to store small/medium-scale models, the analysis results should be considered in the design of model repositories in the cloud. With this aim, we have designed and developed a generic architecture to evaluate each persistence technology under similar situations