Catholic University College of Ghana Fiapre-Sunyani

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Catholic University College of GhanaFiapre-Sunyan
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DATABASE SOFTWARE DEVELOPMENT

• INFORMATION TECHNOLOGY II

Audrey Asante, Faculty of ICST
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DATABASE

• Database is an organized collection of integrated
  files.
• Database may be shared or distributed.
• Shared database is shared by users in one company
  or organization in one location. Shared databases
  can be found in local area networks.

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• Distributed database is one that is stored on
  different computers in different locations
  connected by a client/server network. An example
  is the bank
• Who is a database administrator?
• A person who coordinates all related activities
  and needs for a corporations database.

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• What is the responsibility of a database
  administrator?
• System Security
• Backup and recovery
• Performance monitoring
• Database design, implementation and operation
• Coordination with users

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Database Storage Hierarchy

• It consists of the levels of data stored in a
  computer file bits, bytes (characters), fields,
  records, files and databases.
• Field is a unit of data consisting of one or more
  characters. Example is Name, Address, Social
  Security No
• Record is a collection of related fields. Example
  is the persons name or address or social
  security no

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• File is a collection of related records. Example
  is data collected on everyone.
• Database is an organized collection of integrated
  files. Example is a database of a company

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Key Field

• It is a field that is chosen to uniquely identify
  a record so that it can be easily retrieved and
  processed.

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File Management System

• File-based system a collection of application
  programs that perform services for the end-users
  such as the production of reports. Each program
  defines and manages its own data.

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File Management System

• Disadvantages
• Data redundancy or duplication
• Lack of data integrity
• Separation and isolation of data
• Incompatible file formats
• Data dependence

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Database Management System

• A software system that enables users to define,
  create, maintain, and control access to the
  database.

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Database Management System

• Advantages
• Control of data redundancy
• Data consistency
• Improved security
• Enforcement of standards
• Improved data accessibility and responsiveness

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Database Management System

• Disadvantages
• Cost
• Security
• Privacy
• Additional hardware cost
• Complexity

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TYPES OF DATABASE ORGANIZATION

• Hierarchical
• Network
• Relational
• Object Oriented

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Hierarchical Database

• In this type of database, fields or records are
  arranged in related groups resembling a family
  tree, with lower-level records subordinate to
  higher-level records. A lower-level record is
  called a child, and a higher-level record is
  called a parent. The parent record at the top of
  the database is called the root record. A parent
  in a hierarchical database may have more than one
  child, but a child always has only one parent.
  This is called a one-to-many relationship. Used
  principally on mainframes

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Network Database

• A network database is similar to a hierarchical
  DBMS. The difference is that each child record in
  the network database can have more than one
  parent record. In the network database, a child
  record is identified as a member whiles a parent
  is referred to as owner. This is also principally
  used with mainframes. The network database is
  more flexible than hierarchical because different
  relationships may be established between
  different branches of data.

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Relational Database

• Relational database relates or connects data in
  different files through the use of a key field,
  or common data element. Data elements are stored
  in different tables made up of rows and columns.
  All related fields must have a key field that
  uniquely identifies each row. It is more flexible
  than hierarchical and network database models.

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Object Oriented Database

• This type of database handles new data types,
  including graphics, audio, and video which can be
  combined with text into a multimedia format. An
  object oriented database system uses objects
  software written in small, reusable chunks, as
  elements within database files. An object
  consists of data in the form of text, sound,
  video and pictures and instructions on the action
  to be taken on the data.

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Features of DBMS

• Data Dictionary a procedures document or disk
  file that stores definitions or a description of
  the structure of data used in the database. It
  may monitor the data being entered to make sure
  it conforms to the rules defined during data
  definition such as field name, field size, type
  of data.

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Features of DBMS

• Query Language is an easy-to-use computer
  language for making queries to a database and for
  retrieving selected records.
• Utilities programs that allow one to maintain
  the database by creating, editing, and deleting
  data, records and files.
• Report Generator a program users may employ to
  produce an on-screen pr printed document from all
  or part of a database.

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Features of DBMS

• Access Security a feature allowing database
  administrators to specify different access
  privileges for different users of a DBMS
• System Recovery a feature that enables database
  administrators to recover contents of the
  database in the event of a hardware or software
  failure.

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Software development

• Algorithms are a set of ordered steps for solving
  a problem.
• A program is a list of instructions that the
  computer must follow in order to process data
  into information.

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• Application software may be packaged or
  customized.
• Packaged software is the kind that one buys from
  a computer store or mail-order house or download
  from a vendors website, which is the kind used
  by most PC users
• Packaged software is an off-the-shelf prewritten
  program developed for sale to the general public.
• Share and freeware

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Customized software

• It is a software designed for a particular
  customer. It is an application program that is
  created or custom-made. Customized software is
  written to perform a task that cannot be done
  with packaged software.

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Programming

• It is a specialized form of the age old process
  of problem solving. Problem solving typically
  involves four steps
• Understanding the problem defining the problem
  clearly
• Devising a plan for solving the problem what
  resources are available? people? information? a
  computer? Software? Data? How might those
  resources be put to work to solve the problem?
• Carrying out the plan this phase often overlaps
  with the previous step, since many problem
  solving schemes are developed on the fly
• Evaluating the solution is the problem solved
  correctly? Is this solution applicable to other
  problems?

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Programming process

• There are four step process
• Defining the problem
• Devising, refining, and testing the algorithm
• Writing the program
• Testing and debugging the program
• Most programming problems are far too complex to
  solve all at once. To turn a problem into a
  program, a programmer typically creates a list of
  smaller problems.

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• Each of these smaller problems can be broken into
  subproblems that can be subdivided in the same
  way. This process, called stepwise refinement, is
  similar to the process of developing an outline
  before writing a paper or a book. Programmers
  sometimes refer to this type of design as
  top-down design because the design process starts
  at the top, with the main ideas, and works down
  to the details

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• The result of stepwise refinement is an
  algorithm-a set of step-by-step instructions
  that, when completed, solves the original
  problem. Programmers typically write algorithms
  in a form called pseudocode (a cross between a
  computer language and plain english). When the
  details of an algorithm are in place, a
  programmer can translate it from pseudocode into
  a computer language.

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Control structures

• A computer cant understand this algorithm, but
  the pseudocode is clear to any person familiar
  with control structures (logical structures that
  control the order in which instructions are
  carried out).
• This algorithm uses three basic control
  structures sequence, selection, and repetition

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• Sequence control structure is a group of
  instructions followed in order from the first
  through the last. Eg.
• Set answer to a random value between 1 and 100
  display guess a number between 1 and 100
• Set counter to 0
• Repetition control structure is a looping
  mechanism. It allows a group of steps to be
  repeated several times, usually until some
  condition is satisfied.

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• A selection (or decision) is used to make logical
  decisions. That is to choose between alternative
  courses of action depending on certain
  conditions. It typically takes the form of
  if(some condition is true), then(do something)
  else (do something else)

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Testing the algorithm

• Testing the algorithm is the next step but not
  the same as testing the program. This is testing
  designed to check the logic of the algorithm. We
  can test it by following the instructions using
  different sets of numbers.

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Programming languages and methodologies

• Low level languages
• Machine language
• Assembly language a language thats functionally
  equivalent to machine language but is easier for
  people to read, write, and understand.
  Programmers use alphabetic codes that correspond
  to the machines numeric instructions.
• High level languages it falls between natural
  human languages and precise machine languages

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• High level programs hides most of the nitty
  gritty details of the machine operations from the
  programmer.
• High level language allows the programmer to
  focus on what to do, while assembly language
  forces the programmer to focus on how to do it.
• It allows transportation from one machine to the
  other
• They need to be partially rewritten to adjust to
  differences among hardware, compilers, operating
  systems, and user interfaces

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• Structured programming a technique to make the
  programming process easier and more productive.
  It breaks the big, complicated machine into more
  manageable modules, each of which has a clearly
  defined task. Modular programs are easier to
  understand and debug
• A programmer combines the modules using sequence,
  repetition and selection (basic control
  structures)

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• Object oriented programming it is a collection
  of objects. Objects contain both data and
  instructions and can send and receive messages.
  OOP makes it easy to use features from one
  program in other programs, so programmers dont
  have to start from scratch with every new
  program.

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Visual programming

• It enables programmers to create large portions
  of their programs by drawing pictures and
  pointing to on-screen objects, eliminating much
  of the tedious coding of traditional programming.
  It saves hours of coding time, especially when
  creating user interfaces

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Languages for users

• Some computer languages are designed with
  nonprogrammers in mind
• Macro languages (scripting languages) are built
  into many applications, utilities and operating
  systems eg. Macro in access, spreadsheet to build
  a program, vba in office
• Fourth generation languages

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Fourth Generation Languages

• 4GLs use English-like phrases and sentences to
  issue instructions
• They are nonprocedural, not like pascal, c and
  basic which are procedural languages.
• Non procedural languages enable users to focus on
  what needs to be done, not on how to do it.
• It also increases productivity because
  programmers can often get results by typing a few
  lines of code rather than a few pages.
• Eg. Query language

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Programming for the web
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PROGRAMMING

• It is also called software engineering. It is a
  multistep process for creating that list of
  instructions.
• There are five steps
• Clarify the problem
• Design a solution
• Code the program
• Test the program
• Document and maintain the program

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Clarify the programming needs

• Clarify objectives and users
• Clarify desired outputs
• Clarify desired inputs
• Clarify desired processing
• Feasibility of implementing the program
• Document the analysis

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Feasibility

• Technical feasibility can the required hardware
  and software be purchased or developed? Is the
  technology reliable? Does the system provide for
  accurate, reliable and secure data?
• Economic feasibility cost, good investment
• Operational feasibility needs of the
  organization, changes in the work procedure,
  system be developed on a timely schedule
• Organizational support goals and strategy, legal
  implications

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Data collection techniques

• Document review
• Interview
• Questionnaire
• Observation
• sampling

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Modeling tools

• Graphic representation of a system
• System flowchart
• Data flow diagram
• Data dictionaries
• Decision tables

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Design the program

• User interface design
• Database design
• Process design

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3. Code the program

• A programming language is a set of rules that
  tells the computer what operations to do.

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4. Test the program

• Desk checking is simply reading through or
  checking the program to make sure that its free
  of errors and that the logic works
• Debug the program means to detect, locate and
  remove al errors in a computer program. The
  debugging step is sometimes called alpha testing
• Run real-world data it is sometimes alled beta
  testing

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DOCUMENT AND MAINTAIN THE PROGRAM

• Prepare user documentaton