System Analysis and Design - Mr. Ahmad Al-Ghoul In this sequence we will discuss the data dictionary and how the analyst can use it to document data elements and data structures

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis Data Dictionary A data dictionary, or data repository, is a central storehouse of information about the system’s 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 it’s content and any other relevant information. Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 ( ) Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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) Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis

System Analysis and Design System Analysis 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 Avicenna System Analysis and Design System Analysis