Agricultural to Industrial to Information Age

• Data– Bits and Bytes– e.g. 5184424028

• Information– organized and presented in a form suitable for

decision making– e.g. (518)442-4028

• Knowledge

Desirable Attributes of Information

• Shareable

• Transportable

• Secure

• Accurate

• Timely

• Relevant

Where do companies get information from?

• They buy it– Consultants, publications, news services etc.

• They generate it– Computer systems (programs process data

stored in databases)– Employees (apply experience and intelligence)

Where do we store Intangible Assets -- Information?

• In people’s heads

• On paper

• In card-files

• In computers

Entities, Attributes, and Relationships

• Entity – a person, place, thing, or event

• Attribute – a property of an entity– For the entity “Person,” attributes could include

eye color and height

• Relationship – an association between entities– Publishers are related to the books they publish,

and a book is related to its publisher

Terminology

• Fields - attribute

• Domain -Description of allowed values for an attribute

• Records - logically connected set of one or more fields.

• Files - collection of records

History of Data Processing

• Manual record-keeping– High labor costs and human errors

• Data file – stores information on a single entity and the attributes of that entity

• Database – a structure that can store information about multiple types of entities, the attributes of these entities, and the relationships among the entities

Limitations of File-Based Systems

• Separation and Isolation of Data

• Duplication of Data

• Data dependence

• Incompatibility of files

• Fixed queries / proliferation of application programs / pressure on DP staff

Database

• A self-describing collection of integrated records• Properties of a Database:

– It represents some aspect of the real world

– It is a logically coherent collection of data with some inherent meaning

– It is designed, built, and populated with data for a specific purpose

– It has users and applications

Spreadsheet or Database?

• Data size• Data storage format• Data structure

– extent to which relationships among data items are fixed

• Data sharing• Data control

– degree of data input editing and validating

Static Dynamic

Low Low

Low Low Low

HighHigh

High High High

Structure

Sharing

Control Low High

SOLUTION

Spreadsheet DatabaseEitherDB

DBMS• A software system that :

– Enables users to define, create and maintain the database

– Provides controlled access to this database

DBMS components

• Machine– Hardware– Software

• Data

• Human– Procedures– People

Data Life Cycle

• Data acquisition– data modeling and populating with ultimate

goal of storing data

• Data use– Combines data that has been previously stored

and interprets output in a decision making context (Data Warehousing)

Data acquisition

• Logical database design– E/R diagrams, normalization, database models

• Physical database design– Integrity constraints, indexes, denormalization

• Populating the database– data entry, import, download

• Update records– data dictionary, metadata

Data Use• Define view

– Query design, DDL (SQL or QBE)

• Retrieve data– Query performance and optimization, concurrency

controls

• Manipulate data– Sort, aggregate, classify, analyze

• Present results – Reports, forms

Access Database Objects• Tables

– Stores data as records

• Queries– Answers questions about the database

• Forms– Presents data using a customized layout

• Reports– Formats the data (primarily for printouts)

• Macros– Used to automate repetitive tasks

• Modules• Pages

Users• Administrators

– Data Administrator– Database Administrator

• Database designers– Conceptual and logical design (WHAT?)– Physical design (HOW?)

• Application programmers• End users

– naïve (e.g checkout assistant)– sophisticated

Everyday Database Systems

• Supermarket

• Credit card

• Travel Agent

• Insurance

• Library

• University

Applications of DBMS

• Airline reservations systems– Reservations (customer name, assigned seat)– Flights (airports, arrival and departures)– Tickets (prices, requirements, availability)

• Banking systems– Customers (names, addresses, accounts, loans)

• Corporate records– Accounts (payable, receivable)– Employees (names, addresses, salary, benefits)

Creating a Table in Access

• Datasheet view– To add, delete or edit records

• Design View– To define table the initially and specify its

fields

Custom Tables

• Validation rules

• Input masks

• Default values

• Lookup fields

• Format

Advantages ofDatabase Processing

• Getting more information from the same amount of data– When all the data for various systems are stored

in a single database, the information becomes available, as well as the process of retrieving the information can be quick and easy

Advantages ofDatabase Processing

• Sharing of data– Several users can have access to the same piece of data

(Concurrency control allows shared access)

• Balancing conflicting requirements– A person or group, often called Database

Administration/Administrator (DBA) can structure the database in such a way that it benefits the entire organization, not just a single group

Advantages ofDatabase Processing

• Controlling redundancy– Not only saves space, but makes the updating

process easier

• Consistency– Consistency is a direct result of redundancy, so

by reducing redundancy, there is much less potential for this sort of inconsistency with the database approach

Advantages ofDatabase Processing

• Integrity– An integrity constraint is a rule that must be followed

by data in the database• Example: Not allowing a person’s age to be lower than zero

• Security– The prevention of access to the database by

unauthorized users

– Recovery control restores the data to previous consistent state after hardware/software failure

Advantages ofDatabase Processing

• Increasing productivity– A good DBMS comes with many features that

allow users to gain access to data without having to do any programming at all

• Data independence– A property that allows the structure of a

database to be changed without the programs that access the database having to change

Disadvantages ofDatabase Processing

• DBMS size– DBMSs are large programs that occupy a large

amount of disk space as well as internal memory

• DBMS complexity– The complexity and breadth of the functions

provided by a DBMS make it a complex product to use

Disadvantages ofDatabase Processing

• Greater impact of a failure– A failure on the part of any one user that

damages the database in some way may affect all the other users on the system

• More difficult recovery– If the database is being updated by a large

number of users, all updates must be redone since the time of its restoration

When can an organization justify a database?

• Application needs are constantly changing• Rapid access is required for ad hoc queries• Need to reduce long lead times and high

development costs for new systems• Data elements are shared by users• Need to communicate and relate data across

functional and departmental boundaries• Need to improve quality of data resources and

control access to them

History of DBMS

• IBM developed the Generalized Update Access Method (GUAM) in 1964 for North American Rockwell, the prime contractor for the APOLLO project

• GUAM was made available for the general public under the name Data Language/I (DL/I) in 1966

History of DBMS

• DL/I became the data management component for the Information Management System (IMS), which was the dominant DBMS for many years

• In the mid-1960s, General Electric developed Integrated Data Store (I-D-S)

History of DBMS

• First generation– Hierarchical and network models

• Second generation– Relational models

• Third generation– Object oriented models

Data Models

• Record Based– Hierarchical (60’s)– Network (70’s)– Relational (80’s)

• Object Based– Entity-Relationship (70’s)– Semantic data models (80’s)– Object-oriented (90’s)

Record-Based Data Models

• Hierarchical– Parent-child relationships with only one parent

(N:1 relationships are not supported)

• Network– Extends hierarchical model by allowing

multiple parents– Associations are created via pointers

• Relational

Hierarchical Model

• Perceived by the user as a collection of hierarchies, or trees

• More restrictive structure than a network model

• GUAM, DL/I, and IMS are examples of DBMSs that conform to the hierarchical model

Network Model

• Perceived by the user as a collection of record types and relationships between these record types

• I-D-S is an example of a DBMS that conforms to the network data model

Assignment 1

• MS Access 2000

• Pages AC 2.34 –2.36

• #1-16