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NATURE OF NATURE OF DATADATA

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Three Realms Used to Three Realms Used to Describe DataDescribe Data

Reality (Real World)Reality (Real World)Metadata (Data Metadata (Data Definition)Definition)

Data (Data Occurences)Data (Data Occurences)

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1. Reality1. RealityIt consist of the It consist of the organization itself, the organization itself, the various components of the various components of the organization and the organization and the environment in which the environment in which the organization operates.organization operates.

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EntityEntityAny object or even about which Any object or even about which

the organization chooses to the organization chooses to collect and store datacollect and store data

Ex. Employee, Product, Ex. Employee, Product, Computer or it may be an Computer or it may be an intangible item such as bank intangible item such as bank account, a cost center, a part account, a cost center, a part failure or an airline flightfailure or an airline flight

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Entity ClassEntity ClassA collection of entities that A collection of entities that

posses similar posses similar characteristicscharacteristics

Ex. Entity class are Ex. Entity class are customers, students and customers, students and patientpatient

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AttributeAttributeA property of an entity A property of an entity that we choose to that we choose to record.record.

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IdentifierIdentifierUnique property of an Unique property of an

entity entity

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2. METADATA2. METADATAInformation about the Information about the data in organizationdata in organization

Stored and maintained Stored and maintained in the organization’s in the organization’s data dictionary or data dictionary or directorydirectory

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Data ItemData ItemA unit factA unit factThe smallest name unit of The smallest name unit of

data in a database therefore data in a database therefore the smallest unit of data the smallest unit of data that has meaning to a userthat has meaning to a user

Also called as data Also called as data elements, fields or attributeselements, fields or attributes

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Data AggregateData AggregateA collection of data items A collection of data items

that is named and that is named and referenced as a whole.referenced as a whole.

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RecordRecordA named collections of A named collections of

data items and/or data data items and/or data aggregatesaggregates

Most organization define Most organization define one record type for each one record type for each entity/classentity/class

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KeyKeyA data item used to identify a recordA data item used to identify a recordThe primary key of a record The primary key of a record

corresponds to the identifier of a corresponds to the identifier of a real-worldreal-world

A secondary key is does not uniquely A secondary key is does not uniquely identify a record but identifies a identify a record but identifies a number of records in a set that share number of records in a set that share same propertysame property

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3. Data3. DataIt consists of occurrencesIt consists of occurrencesA file is named collection of A file is named collection of

all occurrences of a given all occurrences of a given record typerecord type

A file maybe visualized as A file maybe visualized as two-dimesional called flat filetwo-dimesional called flat file

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Data Data HierarchyHierarchy

The basis for any The basis for any information information

processing activity processing activity involving databasesinvolving databases

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BitsBitsCharacterCharacter

FieldFieldRecordRecordFileFile

DatabaseDatabase

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BitsBitsBinary Digits of 0’s and Binary Digits of 0’s and 1’s1’s

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CharacterCharacterRepresented by a group of Represented by a group of

bits that are configured bits that are configured according to an encoding according to an encoding system, such as the ASCIIsystem, such as the ASCII

Same as ByteSame as ByteEx. A, 1, E, @Ex. A, 1, E, @

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FieldFieldThe lowest level in the The lowest level in the

data hierarchy at which we data hierarchy at which we can derive any meaning can derive any meaning from the datafrom the data

Ex. Last Name, Age, CityEx. Last Name, Age, City

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RecordRecordA description of an event A description of an event

or an itemor an itemGroup of related fieldsGroup of related fieldsEx. Student Record, Ex. Student Record,

Employee RecordEmployee Record

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FileFileA collection of related A collection of related

recordsrecordsSorted merged and Sorted merged and

processed by a key fieldprocessed by a key fieldEx. Personal FileEx. Personal File

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DatabaseDatabaseA collection of non-A collection of non-

redundant data which can redundant data which can be shared by different be shared by different application systems.application systems.

Ex. Company DatabaseEx. Company Database

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The Traditional The Traditional Approach to Data Approach to Data

ManagementManagement

- Focuses on the data - Focuses on the data processing needs of processing needs of

individual departments in individual departments in the organizationthe organization

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File Processing File Processing SystemSystem

Refers to the use of Refers to the use of computer files to store data computer files to store data in persistent memory, in persistent memory, wherein the data is store wherein the data is store even after the computer even after the computer has been turned off and has been turned off and restartedrestarted

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Note:Note:File processing is an useful File processing is an useful

alternative to a database only alternative to a database only where the information is only where the information is only going to be accessed by a going to be accessed by a single user, where speed of single user, where speed of data input is vital and where the data input is vital and where the amount of data being stored is amount of data being stored is relatively smallrelatively small

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The Emergence The Emergence of the Databaseof the Database

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1950s and Early 1950s and Early 1960s1960s

Data processing using Data processing using magnetic tapes for storagemagnetic tapes for storage

Tapes provide only Tapes provide only sequential accesssequential access

Punched cards for outputPunched cards for output

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Late 1960s & 1970sLate 1960s & 1970sHard disk allow direct acces Hard disk allow direct acces

to datato dataNetwork and hierarchical Network and hierarchical

data models in widespread data models in widespread useuse

High performance High performance transaction processingtransaction processing

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1980s1980sResearch relational prototypes Research relational prototypes

evolve into commercial systems.evolve into commercial systems.SQL becomes industrial standardsSQL becomes industrial standardsParallel and distributed database Parallel and distributed database

systemssystemsObject-oriented database systemsObject-oriented database systems

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1990s1990sLarge decisions support and Large decisions support and

data mining applicationsdata mining applicationsLarge multi-terabyte data Large multi-terabyte data

warehousewarehouseEmergence of web Emergence of web

commercecommerce

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2000s2000sXML and XQUERY XML and XQUERY

standardsstandardsAutomated Database Automated Database

AdministrationAdministration

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Database Database ApproachApproach

-Represents a different Represents a different concept in information concept in information resource managementresource management- The concept is rooted in The concept is rooted in an attitude of sharing an attitude of sharing common data resourcescommon data resources

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Electronic Electronic SpreadsheetsSpreadsheets

Also known as Flat File Also known as Flat File DatabasesDatabases

Faster than manual database Faster than manual database but for a large number of but for a large number of entries are very slowentries are very slow

Data is duplicated and often Data is duplicated and often misfiledmisfiled

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Advantages of Advantages of the Database the Database

ApproachApproach

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1. Program-Data 1. Program-Data IndependenceIndependence

The data will be held in such The data will be held in such a way that if the user make a way that if the user make changes to the structure of changes to the structure of the database, the program the database, the program that access the data will not that access the data will not be affectedbe affected

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2. Data Consistency2. Data ConsistencyDue to the fact that each Due to the fact that each

data item is held only data item is held only once, there is no danger of once, there is no danger of an item being updated on an item being updated on one system and not on the one system and not on the otherother

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3. Controlled 3. Controlled RedundancyRedundancy

Reducing to a minimum Reducing to a minimum the number of data items the number of data items which are duplicated in a which are duplicated in a databasedatabase

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4. Data Integrity4. Data IntegrityThe protection of data from The protection of data from

accidental, deliberate accidental, deliberate corruption or modification in corruption or modification in the databasethe database

The ability to specify The ability to specify constraints on dataconstraints on data

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5. Data Security5. Data SecurityOnly authorize users gain Only authorize users gain

access to the dataaccess to the dataAlso to protect the rights of Also to protect the rights of

individual and organization to individual and organization to restrict access to information restrict access to information which relates to them and is which relates to them and is of a private natureof a private nature

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6. Data Integration6. Data Integration Data are organized into a Data are organized into a

single, logical structure, with single, logical structure, with logical relationships defined logical relationships defined between associated data between associated data entitiesentities

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7. Data Sharing7. Data SharingA database is intended to A database is intended to

be shared by all authorized be shared by all authorized users in the organization.users in the organization.

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8. Enforcement of 8. Enforcement of StandardStandard

Has the authority to define Has the authority to define and enforce data standards.and enforce data standards.

All changes to data standards All changes to data standards would have to be approved would have to be approved by database administrationby database administration

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9. Ease of Application 9. Ease of Application DevelopmentDevelopment

The cost and time for The cost and time for developing new business developing new business applications are greatly applications are greatly reducedreduced

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10. Data Accessibility 10. Data Accessibility and Responsivenessand Responsiveness

Provides multiple retrieval Provides multiple retrieval paths to each item of data, paths to each item of data, giving a user much greater giving a user much greater flexibility in locating and flexibility in locating and retrieving data than with data retrieving data than with data filesfiles

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Disadvantages of Disadvantages of Database Database ApproachApproach

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1. New, Specialized 1. New, Specialized PersonnelPersonnel

Need to hire o train individuals Need to hire o train individuals to maintain the new database to maintain the new database software, develop and enforce software, develop and enforce new programming standards new programming standards to achieve the highest possible to achieve the highest possible performanceperformance

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2. Need for Explicit 2. Need for Explicit BackupBackup

Minimal data redundancy, Minimal data redundancy, with all its associated with all its associated benefits, also may fail to benefits, also may fail to provide backup copies of provide backup copies of datadata

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3. Interference with 3. Interference with Shared DataShared Data

The concurrent access to The concurrent access to shared data via several shared data via several application programs can application programs can lead to some problemslead to some problems

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4. Organizational 4. Organizational UsageUsage

A shared database requires A shared database requires a consensus on data a consensus on data definitions and ownership definitions and ownership as well as responsibilities as well as responsibilities for accurate data for accurate data maintenancemaintenance

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Elements of Elements of Database Database ApproachApproach

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Enterprise Data Enterprise Data ModelModel

Graphical model showing Graphical model showing high-level entities and high-level entities and relationships for the relationships for the organizationorganization

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Relational Relational DatabaseDatabase

Database technology Database technology involving tables (relation) involving tables (relation) representing entities and representing entities and primary/foreign keys primary/foreign keys representing relationshipsrepresenting relationships

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Use of Internal Use of Internal TechnologyTechnology

Networks and Networks and telecommunications, telecommunications, distributed databases, client distributed databases, client server and tier architectureserver and tier architecture

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Database Database ApplicationsApplications

Application programs used Application programs used to perform activities for to perform activities for database usersdatabase users

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The Database The Database PhilosophyPhilosophy

Each piece of information be entered Each piece of information be entered and stored just onceand stored just once

Every authorized user have quick an Every authorized user have quick an easy access to any of the stored dataeasy access to any of the stored data

Data is entered, maintained and Data is entered, maintained and access in ways that they are not access in ways that they are not dependent on any particular dependent on any particular application programsapplication programs

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Database Database SystemSystem

- An integrated system of - An integrated system of computer, hardware, computer, hardware,

software and human user.software and human user.

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Components of Components of Database Database

EnvironmentEnvironmentData

Administrator

System Developer End User

User Interface

Application Programs

DBMS DatabaseRepository