{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture2(1) - Lecture 2 on Extended Entity Relationship...

Info icon This preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
01/11/12 Lecture 2 on Extended Entity Relationship Model This lecture is to describe the methodology of designing an Extended Entity Relationship Model as a conceptual schema for relational database with data semantics of weak entity, cardinality, isa, generalization, aggregation, participation, categorization and n-ary relationship.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
01/11/12 Data Model A data model is defined for describing the structure and processing of a database. Database models have two major components: 1. Data definition language(DDL) is a database language that defines the structure of the database – data and relationship. It also provides facility for expressing a variety of user views and database constraints. 2. Data manipulation language(DML) is a database language for describing operations on the data that serve to express queries and other manipulation of data. Two types of DML exist: Procedural DML – describing actions to be performed (how). Nonprocedural DML – describing what data is wanted without describing how to obtain it.
Image of page 2
01/11/12 Ansi X4 Architecture of Data Modeling
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
01/11/12 Data independence 1. Logical data independence – The changes of logical schema will not affect the view of the application program processing. 2. Physical data independence – The changes of the physical (internal) schema will not affect the application program processing.
Image of page 4
01/11/12 Application of data models to database design Database design can be summarized as follows: 1. Begin with the requirements definition. 2. Express tentative conceptual database design in terms of a logical database model. 3. Review design in light of requirements. 4. Convert conceptual design to a logical design using the appropriate logical data model, the one that matches the DBMS to be used. 5. Implement the database using the features of the DBMS.
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
01/11/12 Use of models in database design Specification Entity-relationship or UML conceptual Schema Relationship Definitions Supporting Documentation Classes Diagrams and Supporting Documentation Conceptual Design Logical Design OR Relational Database implementation Object-Oriented database Implementation Database Design Physical Design
Image of page 6
01/11/12 Entity Relationship(ER) Model The Entity Relationship Model is a diagramatic technique for conceptual database design. It serves as an informal representation to model the real world by adopting the more natural view that the real world consists of entities and relationship; and incorporating important semantic information into the model. The model can achieve a high degree of data independence and is based on set theory and relation theory. It can be used for designing conceptual database.
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
01/11/12 Component of entity-relationship model 1. Entity set – an entity set (i.e. entity type) or an entity (i.e. entity instance) is an important distinguishable object for an application.
Image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern