Transcript Agricultural to Industrial to Information Age

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
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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?
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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
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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
Structure
Low
Sharing
Control
Low
High
Spreadsheet
Dynamic
High
Low High
DB
Low
Low
Either
SOLUTION
High
High
Low
Database
High
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
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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
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Validation rules
Input masks
Default values
Lookup fields
Format
Advantages of
Database 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 of
Database 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 of
Database 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 of
Database 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 of
Database 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 of
Database 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 of
Database 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