CHAPTER 5 MANAGING ORGANIZATIONAL DATA AND INFORMATION

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CHAPTER 5MANAGING ORGANIZATIONAL DATA AND
INFORMATION
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Data Hierarchy and Database Concepts

• Field - a logical grouping of characters into a
  word, a small group of words, or a complete
  number
• Record - a logical grouping of related fields
• File - a logical grouping of related records
• Database - a logical grouping of related files
• Entity - a person, place, thing, or event about
  which information is maintained
• Attribute - each characteristic or quality
  describing a particular entity
• Key - field that has some identifying information
• Primary Key - field that uniquely identifies the
  record

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Storing and Accessing Records

• Indexed Sequential Access Method (ISAM)
• uses an index of key fields to locate individual
  records
• index - lists the key field of each record and
  where that record is physically located in
  storage
• track index - shows the highest value of the key
  field that can be found on a specific track
• Direct File Access Method
• uses the key field to locate the physical address
  of a record
• transform algorithm - translates the key field
  directly into the records storage location on
  disk

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Traditional File Environment
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Introduction to Information Technology Turban,
Rainer and Potter Chapter 4 Computer Software

• The organization has multiple applications with
  related data files

Each application has a specific data file related
to it, containing all the data records needed by
the application
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Problems with the File Environment

• data redundancy - the same piece of information
  could be duplicated in several places
• data inconsistency - the various copies of the
  data no longer agree
• Violation of data a integrity data isolation -
  difficulty in accessing data from different
  applications
• Violation of application/data independence

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DBMS History

• Generalized Update Access Method (at the
  beginning of 60s)
• Integrated Data store (at the beginning of 60s)
• GUAM is transformed into Information Management
  system (in the middle of 60s)
• Data Base Task Group (1965)

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DBMS History (continued)

• Relational data model had been introduced by Codd
  (1970) second-generation DBMSs
• Third-generation DBMSs Object-Oriented and
  Object-Relational
• Multidimensional data model
• Hypermedia data model

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Database The Modern Approach

• Database architecture
• Centralized database
• Distributed database
• replicated database - complete copies of the
  entire database are delivered to many locations
• partitioned databases - these are subdivided, a
  portion of the entire database in each location

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Centralized vs. Distributed Databases
User New York
User Los Angeles
Centralized Database
Distributed Database
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Creating a Database

• Conceptual design - description of the database
  from the user or business perspective
• Logical design abstract model of a database
  showing how the data should be structured and
  arranged including relationships between data
• Physical design - shows the way a database is
  actually arranged on storage devices

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Entity-relationship (ER) modeling

• process of planning the database design
• ER diagram graphical presentation of logical
  data model
• Entity classes ? Instance ? Identifiers ?
  Relationships
• Degree of a relationship set is a number of
  participating entity sets
• Binary relationships
• One-to-one (11)
• One-to-many (1N)
• Many-to-many (NN)

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Logical Data Models

• In a logically structuring database, businesses
  need to consider the characteristics of the data
  and how the data will be accessed.
• Three common data models
• Hierarchical,
• Network,
• Relational

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Hierarchical Database Model

• structures data into an inverted tree in which
  each record contains two elements rigidly
• a single root or master field, often called a
  key, which identifies the type location or
  ordering of the records
• a variable number of subordinate fields,which
  defines the rest of the data within a record
• all fields have only one parent, each parent
  may have many children
• Advantage speed and efficiency
• Problem access to data is predefined before the
  programs and each relationship must be
  explicitly defined when the database is created

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Network Database Model

• creates relationship among data through a
  linked-list structure in which subordinate
  records (members) can be linked to more than one
  data element (owner)
• pointer - explicit link, storage addresses that
  contain the location of a related record
• many-to-many relationships are possible
• complexity for every set of linked data
  elements, a pair of pointers must be maintained

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Relational Database Model

• based on a simple concept of tables called
  relations in order to capitalize on
  characteristics of rows and columns of data
• Each table corresponds to Entity class
• Each row (or tuple) contains an instance of a
  given Entity a record
• A cell contains an attribute value of a
  particular instance of entity and is called a
  field or data element

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Rules to create a relation

• Each relation (table) must have a unique name
• Each tuple(record) in the relation (table) must
  have a primary key
• Records may be added or stored in a relation in
  any physical order
• Links among the data are implicit.

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Basic Data Manipulations (Relational Databases)

• Support retrieving only necessary data
• Selecting eliminating rows according to certain
  criteria
• Projecting eliminating columns according to
  certain criteria
• Joining combining columns from two or more
  tables

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Normalization

• method for data arrangement to reduce data
  redundancy and to maximize data integrity
• First Normal Form each field must contain
  atomic value
• Second Normal Form each record of 1NF table
  must be identify uniquely
• Third Normal Form a table in 2NF should not
  contain extra non-key data related to non-key
  data from another table.

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Database Management Systems

• A software program (or group of programs) that
  provides access to a databases
• Provides mechanisms for maintaining the integrity
  of stored information, managing security and user
  access, recovering information when the system
  fails, and accessing various database functions
  form an application

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Logical versus Physical View

• Physical view - deals with the actual, physical
  arrangement and location of data in the direct
  access storage devices
• Logical view - represents data in a format that
  is meaningful to a user and to the software
  programs that process that data
• A schema a description of logical structure of
  all data
• A subschema a description of logical view for a
  user

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DBMS Components

• Data model - defines the way data are structured
• Data definition language (DDL)
• Data manipulation language (DML)
• Data Dictionary

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Data Definition Language

• Describes data (type, length, constrains)
• Relationships among data, keys
• Schema and Subschema are developed based on DDL

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Data Dictionary

• Data definitions are stored in the Data
  Dictionary
• Data Dictionary provides
• Standard definitions of data and relationships
  among them
• Assists in designing and programming
• Reduce data redundancy
• Increase data reliability

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Data Manipulation Language

• Collection of instructions and allowable
  parameters for data manipulation
• DML helps to
• Retrieve data
• Update data
• Add data
• Delete data

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Structured Query Language (SQL)

• Standard DDL and DML to query relational
  databases
• Modern DBMSs have SQL dialects
• Many of 4GLs support embedded SQL to query
  database from applications.

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SQL (Example)

• SELECT Course code, Cname, Day, Time, Location
• FROM Sections, Courses
• WHERE Courses.Course code
• (SELECT Course Code
• From Sections
• WHERE Instructor EN 12345)

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Trends in DBMS Development

• Object-oriented databases
• Object-relational databases
• Hypermedia databases
• Data warehouses
• Knowledge databases

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Object-oriented database model

• An object - a small amount of data put together
  with all the data needed in order to perform an
  operation with that data
• An object - similar to an entity is an instance
  of a Class
• Attributes - characteristics that describe the
  state of that object
• Method - an operation, action, or a behavior the
  object may undergo
• Messages the form by which objects interact
  with each other.

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Object-relational Databases

• Applications require to manipulate with audio,
  video and graphical data
• Georeferenced databases
• Multimedia databases

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Hypermedia databases

• stores chunks of information in a form of nodes
• Nodes contain multimedia data
• Nodes are connected by links established by the
  user

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Knowledge Databases

• Consists of 2 parts
• Database
• Rules
• heuristics to evaluate a situation
• Analyzed the data to produce new knowledge

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Data Warehouses

• A data warehouse is multidimensional database
  management system designed to support strategic
  management decision making.
• The data mart is a subset of data warehouse for a
  single aspect of business

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Data WarehousesFramework and View
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Data Warehouses (definition)

• Is a database that contains the following
  characteristics
• Subject oriented
• Nonvolatile
• Integrated
• Time variant

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Data stored in a data warehouses

• Current detailed data
• Historical Data
• Lightly summarized data
• Highly summarized data
• Metadata

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Metadata

• Describes the content of database
• Is divided into
• Technical metadata
• Business metadata

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Multidimensional Database

• the data are intimately related and can be viewed
  and analyzed from different perspectives, which
  are called dimensions
• core of data warehouses
• data are stored in arrays
• consists of at least three dimensions

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Example
Fall 2001
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Example (continue)
Winter 2002
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Example (continue)
Summer 2002
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Data Mining

• provides a means of extracting previously
  unknown, predictive information from the base of
  accessible data in data warehouses
• discovers hidden patterns, correlations, and
  relationships among organizational data
• functions of data mining
• Classification forecasting
• clustering association
• sequencing