61,721 research outputs found

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

    Get PDF
    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

    REVERSE ENGINEERING BASED APPROACH FOR TRANSFERRING LEGACY RELATIONAL DATABASES INTO XML

    Get PDF
    XML (extensible Markup Language) has emerged, and. is being gradually accepted as the standard for data interchange over the Internet. Since most data is currently stored in relational database systems, the problem of converting relational data into XML assumes special significance. Many researchers have already done some accomplishments in this direction. They mainly focus on finding XML schema (e.g., DTD, XML-Schema, and RELAX) that best describes a given relational database with a corresponding well-defined database catalog that contains all information about tables, keys and constraints. However, not all existing databases can provide the required catalog information. Therefore, these applications do not work well for legacy relational database systems that were developed following the logical relational database design methodology, without being based on any commercial DBMS, and hence do not provide well-defined metadata files describing the database structure and constraints. In this paper, we address this issue by first applying the reverse engineering approach described in [2] to extract the ER (Extended Entity Relationship) model from a legacy relational database, then convert the ER to XML Schema. The proposed approach is capable of reflecting the relational schema flexibility into XML schema by considering the mapping of binary and nary relationships. We have implemented a first prototype and the initial experimental results are very encouraging, demonstrating the applicability and effectiveness of the proposed approach

    Egy folyóirat adatait tartalmazó adatbåzis relåciós modelljének elkészítése

    Get PDF
    A Jelenkori tĂĄrsadalmi Ă©s gazdasĂĄgi folyamatok cĂ­mƱ folyĂłiratban az elsƑ megjelenĂ©s Ăłta összesen 895 szerzƑtƑl 482 cikk jelent meg. Annak Ă©rdekĂ©ben, hogy az eddig publikĂĄlt, illetve a kĂ©sƑbbiekben megjelenƑ szĂĄmokban talĂĄlhatĂł informĂĄciĂłk hatĂ©kony mĂłdon kinyerhetƑk legyenek, egy adatbĂĄzis lĂ©trehozĂĄsĂĄnak ötlete merĂŒlt fel. Az adatbĂĄzis elkĂ©szĂ­tĂ©sĂ©hez szĂŒksĂ©ges volt egy magas szintƱ koncepcionĂĄlis modell megtervezĂ©se, majd az alapjĂĄn a logikai adatmodell elkĂ©szĂ­tĂ©se. A folyĂłirat kapcsĂĄn ez az egyed-kapcsolat modell megtervezĂ©sĂ©t, majd relĂĄciĂłs modellĂ© konvertĂĄlĂĄsĂĄt jelentette; ez utĂłbbi ennek az Ă­rĂĄsnak a tĂĄrgya. Az egyed-kapcsolat modell 3 egyedhalmazt, 39 attribĂștumot Ă©s 3 kapcsolatot tartalmazott. A konvertĂĄlĂĄs sorĂĄn ebbƑl szĂŒletett 10 tĂĄblĂĄzat az egyedek adatainak tĂĄrolĂĄsĂĄra – összesen 22 kĂŒlönbözƑ mezƑvel (oszloppal) – Ă©s tovĂĄbbi 3 tĂĄblĂĄzat az egyedhalmazok közötti kapcsolatok biztosĂ­tĂĄsĂĄra. Az Ă­gy kialakĂ­tott modell relĂĄciĂłs adatbĂĄziskezelƑben megvalĂłsĂ­thatĂł Ă©s alkalmas a folyĂłirattal kapcsolatos informĂĄciĂłs igĂ©nyek kiszolgĂĄlĂĄsĂĄra. Abstract: A total of 482 articles by 895 authors have been published in Contemporary Social and Economic Processes since its first publication. In order to efficiently extract the information published so far and in future issues, the idea of creating a database has emerged. To create the database, it was necessary to design a high-level conceptual model and then build a logical data model based on it. In the context of the journal, this meant designing the entity-relationship model and then converting it to a relational model; the latter is the subject of this writing. The entity-relationship model consisted of 3 entity sets with 39 attributes, and 3 relationships. With the conversion, 10 tables were created to store the data of the entities – with a total of 22 different fields (columns) – and another 3 tables to ensure the relationships between the entity sets. The developed model can be created in a relational database manager and is suitable for serving information needs related to the journal

    Relational Database Design for Web-Based Computer Inventory System Jabatan Pelajaran Negeri (JPN) Perak

    Get PDF
    This study was focus on designed database system for web-based computer inventory system for Jabatan Pelajaran Perak namely JPCIS. A methodology is defined for the design of this relational database. The methodology is presented as a systematic guide to the five main phases of database design namely as follows (1) Requirement Analysis, (2) Conceptual Database Design, (3) Logical Database Design, (4) Physical Database Design, and (5) Prototyping. The data requirements are defined and conceptualised using an extended Entity-Relationship Model (ER Model), with the extensions being additional semantics such as relationship, optional relationship, and the generalisation abstractions. There are three categories of users and 15 entities been identified. Cross-Referencing Transaction been used to analyse transactions. The main objective is to understand the functionality of transaction (query) run on the database. In Logical Database Design with involved build and validate local logical design, Data Flow Diagram been drawn to visualized it. Data Flow Diagram been used to analyse transactions. The main objective is to understand the functionality of transaction (query) run on the database. Finally automated prototyping been used to validate the database system and the test shown that it meet the users needs

    Egy folyóirat adatait tartalmazó adatbåzis relåciós modelljének elkészítése

    Get PDF
    A total of 482 articles by 895 authors have been published in Contemporary Social and Economic Processes since its first publication. In order to efficiently extract the information published so far and in future issues, the idea of creating a database has emerged. To create the database, it was necessary to design a high-level conceptual model and then build a logical data model based on it. In the context of the journal, this meant designing the entity-relationship model and then converting it to a relational model; the latter is the subject of this writing. The entity-relationship model consisted of 3 entity sets with 39 attributes, and 3 relationships. With the conversion, 10 tables were created to store the data of the entities – with a total of 22 different fields (columns) – and another 3 tables to ensure the relationships between the entity sets. The developed model can be created in a relational database manager and is suitable for serving information needs related to the journal.A Jelenkori tĂĄrsadalmi Ă©s gazdasĂĄgi folyamatok cĂ­mƱ folyĂłiratban az elsƑ megjelenĂ©s Ăłta összesen 895 szerzƑtƑl 482 cikk jelent meg. Annak Ă©rdekĂ©ben, hogy az eddig publikĂĄlt, illetve a kĂ©sƑbbiekben megjelenƑ szĂĄmokban talĂĄlhatĂł informĂĄciĂłk hatĂ©kony mĂłdon kinyerhetƑk legyenek, egy adatbĂĄzis lĂ©trehozĂĄsĂĄnak ötlete merĂŒlt fel. Az adatbĂĄzis elkĂ©szĂ­tĂ©sĂ©hez szĂŒksĂ©ges volt egy magas szintƱ koncepcionĂĄlis modell megtervezĂ©se, majd az alapjĂĄn a logikai adatmodell elkĂ©szĂ­tĂ©se. A folyĂłirat kapcsĂĄn ez az egyed-kapcsolat modell megtervezĂ©sĂ©t, majd relĂĄciĂłs modellĂ© konvertĂĄlĂĄsĂĄt jelentette; ez utĂłbbi ennek az Ă­rĂĄsnak a tĂĄrgya. Az egyed-kapcsolat modell 3 egyedhalmazt, 39 attribĂștumot Ă©s 3 kapcsolatot tartalmazott. A konvertĂĄlĂĄs sorĂĄn ebbƑl szĂŒletett 10 tĂĄblĂĄzat az egyedek adatainak tĂĄrolĂĄsĂĄra – összesen 22 kĂŒlönbözƑ mezƑvel (oszloppal) – Ă©s tovĂĄbbi 3 tĂĄblĂĄzat az egyedhalmazok közötti kapcsolatok biztosĂ­tĂĄsĂĄra. Az Ă­gy kialakĂ­tott modell relĂĄciĂłs adatbĂĄziskezelƑben megvalĂłsĂ­thatĂł Ă©s alkalmas a folyĂłirattal kapcsolatos informĂĄciĂłs igĂ©nyek kiszolgĂĄlĂĄsĂĄra

    Object-oriented querying of existing relational databases

    Get PDF
    In this paper, we present algorithms which allow an object-oriented querying of existing relational databases. Our goal is to provide an improved query interface for relational systems with better query facilities than SQL. This seems to be very important since, in real world applications, relational systems are most commonly used and their dominance will remain in the near future. To overcome the drawbacks of relational systems, especially the poor query facilities of SQL, we propose a schema transformation and a query translation algorithm. The schema transformation algorithm uses additional semantic information to enhance the relational schema and transform it into a corresponding object-oriented schema. If the additional semantic information can be deducted from an underlying entity-relationship design schema, the schema transformation may be done fully automatically. To query the created object-oriented schema, we use the Structured Object Query Language (SOQL) which provides declarative query facilities on objects. SOQL queries using the created object-oriented schema are much shorter, easier to write and understand and more intuitive than corresponding S Q L queries leading to an enhanced usability and an improved querying of the database. The query translation algorithm automatically translates SOQL queries into equivalent SQL queries for the original relational schema
    • 

    corecore