Data Modeling

Only available on StudyMode
  • Download(s) : 30
  • Published : February 9, 2013
Open Document
Text Preview
Lecture Notes 1

Data Modeling

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

1

• Database: A collection of related data. • Data: Known facts that can be recorded and have an implicit meaning. – An integrated collection of more-or-less permanent data.

• Mini-world: Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university. • Database Management System (DBMS): A software package/ system to facilitate the creation and maintenance of a computerized database. • Database System: The DBMS software together with the data itself. Sometimes, the applications are also included. ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT 2

Evolution of Database System

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

3

Ways of storing data
• Files – ancient times (1960) • Databases
– – – – Hierarchical (1970) Network (1970) Relational (1980) Object (1990)

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

4

File terms
– Record • data items related to a single logical entity (e.g. a student’s information) or row in a table – Field • a place for a data item in a record (first name field in a student record) or a column in a table – File • a sequence of records of the same type (the table) ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT 5

File structures
A file: “STUDENT”
ID Last 3 1 record 2 4 Smith Wood Kent Boone field

First Jane Bob

Grade A C B B

Chuck Dan

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

6

File organization
• Serial
– new records appended

• Sequential
– records ordered in file, usually according to a numeric key

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

7

File structures
• Serial
– list of entries in which the order of entry into the list determines the order of the list ID Last First Grade 3 Smith Jane A 1 2 4 Wood Kent Boone Bob Chuck Dan C B B

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

8

File structures
• Sequential
– list of entries ordered in some way (e.g. numerically or alphabetically)

ID Last 1 2 3 4 Wood Kent Smith Boone

First Grade Bob Chuck Jane Dan C B A B

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

9

Problems with files
– Redundancy • number of files grows with applications, and data is duplicated – Inconsistency • data is updated in one application’s files, but not in another’s – Maintenance problems • changes to data structures mean changes to many programs – Difficulty combining data • business needs may mean users want data from different applications ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT 10

Data Modeling
• It is essential to building a good database. • refers to the process where by data is structured and organized. • Once data is structured, it is usually then implemented into what is called a database management system. The main idea behind these systems to manage vast amounts of both structured and unstructured data. ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT 11

– Unstructured data include documents, word processing, e-mail messages, pictures, and digital video and audio files. – Structured data, what is needed to make a data model (via a data model theory), is found in management systems like relational databases.

• Data Model
– representations of different entity classes that a company wants to possess information about, containing the specifics behind that information, and the relationship among the differing entities and attributes.

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

12

– Both the blueprint and the foundation – A representation of reality, a way to graphically plot your data requirements – A visual model of what your database can look like when you...
tracking img