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System Analysis

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... comprehensive information about the data and processes that make up the system Data Dictionary ... enrolment no. Each ... the data structure ... – PowerPoint PPT presentation

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Title: System Analysis


1
System Analysis
System Analysis and Design
  • - Mr. Ahmad Al-Ghoul

2
Learning Objectives
  • Describe how a data dictionary is used and what
    it contains
  • Create a data dictionary entries for data
    elements
  • Create a data dictionary entries for data
    structure or record

3
Data Dictionary
  • A data dictionary, or data repository, is a
    central storehouse of information about the
    systems data
  • A data dictionary is created when the system is
    developed, and is updated constantly as the
    system is implemented, operated, and maintained
  • An analyst uses the data dictionary to collect,
    document, and organize specific facts about the
    system
  • In addition to describing each data element, data
    structure, data flow, data store, entity, and
    process, the data dictionary documents the
    relationships among these components
  • Without a data dictionary the development of
    large systems becomes difficult.
  • The data dictionary is an effective solution to
    the problem of complicated nature. The main
    purpose of a data dictionary is to provide a
    source of reference in which the analyst , the
    user, the designer can look up find out its
    content and any other relevant information.

4
Data Dictionary
  • Data Elements
  • A data element, also called a data item or field,
    is the smallest piece of data that has meaning
  • Data elements are pieces of data, which need not
    be broken further.
  • Data elements are combined into records, also
    called data structures
  • A record is a meaningful combination of related
    data elements that is included in a data flow or
    retained in a data store
  • Data elements can describe files, data flows, or
    processes.
  • Often a data element is self defining such as
    Student name, enrolment no.
  • Each element should be defined once in the data
    dictionary

5
Data Dictionary
  • Documenting the Data Elements
  • You must document every data element in the data
    dictionary
  • The objective is to provide clear, comprehensive
    information about the data and processes that
    make up the system

6
Data Dictionary
  • Documenting the Data Elements
  • The following attributes usually are recorded and
    described
  • Data element name or label the standard name for
    the data element it should be meaningful to
    users.
  • Type and length type refers to whether the data
    element contains numeric, char, date values.
    Length is the maximum number of char data element
    or the maximum number of digits and numbers of
    decimal positions for numeric data elements.
  • Output format the arrangement of the data
    element when users see it printed in reports or
    displayed on the screen

7
Data Dictionary
  • Documenting the Data Elements
  • Default values the value for the data element if
    a value otherwise is not entered for it.
  • Prompt, column header, field caption the default
    display screen prompt or report column heading
    when the information system outputs the data
    elements.
  • Source the specification for the rogation point
    for the data elements values, the source could be
    a specific form , a department or outside
    organization, anther information system or the
    result of a calculation
  • Security identification for the individual or
    department that has access or update privileges
    for each data elements.
  • Responsible users identification of the users
    responsible for entering and changing values for
    the data elements

8
Data Dictionary
  • Documenting the Data Elements
  • Acceptable values specification of the data
    element domain which, is the set of values
    permitted for the data element these values
    either can be specifically listed or referenced
    in a table, or selected from a specified range of
    values. You also would indicate if a value for
    the data element is optional.
  • Derivation formula if the data element value is
    the result of a calculation, then you show the
    formula for the data element, including
    significant digits and rounding operations if
    any
  • Description or comments part of the data element
    documentation that allows you to provide
    additional definitions, descriptions or notes

9
Data Dictionary
  • Data structure or record
  • Data structures or records are a group of smaller
    structures and elements
  • An algebraic notation is used to represent the
    data structure

10
Data Dictionary
  • Data structure or record
  • Algebraic Notation
  • The symbols used are
  • Equal sign, meaning consists of
  • Plus sign, meaning "and
  • Braces meaning repetitive elements, a
    repeating element or group of elements
  • Brackets for an either/or situation. Either
    one element may be present or anther, but not
    both
  • The elements listed inside are mutually exclusive
  • Parentheses () for an optional element

11
Data Dictionary
  • Data structure or record
  • Each structure or group of elements is analyzed
  • Each element should be analyzed by asking the
    following questions
  • A. Are there many of the field?
  • If the answer is yes, indicate that the field is
    a repeating field using the symbols
  • B. Is the element mutually exclusive of another
    element?
  • If the answer is yes, surround the two fields
    with the symbols
  • C. Is the field an optional entry or optionally
    printed or displayed?
  • If so, surround the field with parenthesis ( )

12
Data Dictionary 2
  • Data Structure or record Example
  • Customer Order Customer Number
  • Customer Name
  • Address
  • Telephone
  • Catalog Number
  • Order Date
  • Available Order Items
  • Merchandise Total
  • (Tax)
  • Shipping and Handling
  • Order Total
  • Method of Payment
  • (Credit Card Type)
  • (Credit Card Number)
  • (Expiration Date)

13
Data Dictionary
  • Documenting the data structure or record
  • Record or data structure name the data structure
    or record name as it appears in the related data
    flows and data stores
  • Definition or description a brief definition
  • Alternate name(s) aliases for the data structure
    or record name
  • Attributes a list of all the data elements
    included in the data structure or record

14
Sequence Summary
  • The data dictionary is the central documentation
    tool for structured analysis
  • A data dictionary is created when the system is
    developed, and is updated constantly as the
    system is implemented, operated, and maintained
  • An analyst uses the data dictionary to collect,
    document, and organize specific facts about the
    system
  • Data elements are pieces of data, which need not
    be broken further.
  • You must document every data element in the data
    dictionary
  • Data elements are combined into records, also
    called data structures
  • An algebraic notation is used to represent the
    data structure

15
Sequence Summary
  • In this Sequence we have
  • Describe how a data dictionary is used and what
    it contains
  • Defined the term data element
  • Create a data dictionary entries for data
    elements
  • Defined the term data structure or record
  • Explained how to use algebraic notation in
    documenting the data structure
  • Create a data dictionary entries for data
    structure or record

16
Reference
  • 1 System Analysis and Design, Sixth Edition
  • Authors Gary B. Shelly, Thomas J. Cashman
    and Harry J. Rosenblatt ,
  • Publisher SHELLY CASHMAN SEWIES.
  • 2 system analysis and design, sixth edition
  • Authors Kenneth E. Kendall and Julie E.
    Kendall
  • Publisher Prentice Hall
  • 3 Modern Systems Analysis and Design Third
    Edition
  • Authors Jeffrey A. Hoffer , Joey F. George,
    Joseph S. Valacich
  • Publisher prentice hall
  • 4 System Analysis and Design, 3rd Edition
  • Authors Dennis, Wixom, Roth
  • Publisher John Wiley sons
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