3/5/2009Computer systems1 Analyzing System Using Data Dictionaries Computer System: 1. Data Dictionary 2. Data Dictionary Categories 3. Creating Data Dictionary

3/5/2009Computer systems2 Data Dictionary n a reference n data about data n metadata n keep clean data – reduce redundancy n collect and coordinates data terms n provide documentation

3/5/2009Computer systems3 Data Repository A larger collection of project information May contain: n information about data n procedural logic and use case n I/O design n data relationships n project requirements and deliverables n project management information

3/5/2009Computer systems4 Information About Data n data flow n data stores n record structures n elements n entities n messages

3/5/2009Computer systems5 I/O Design n Screen n Report

3/5/2009Computer systems6 Data Relationships n data structures n links between data structures

3/5/2009Computer systems7 Project Management Information n delivery schedules n achievements n issues needed resolving n project users

3/5/2009Computer systems8 Data Dictionary Categories n Data flows n data structures n data elements n data stores

3/5/2009Computer systems9 Data Flows Defining the data flows: n ID n Unique descriptive name n general description n source n destination n record entering or leaving n name of the data structure n volume per unit of time n further comments and notations area

3/5/2009Computer systems10 Data Structures Data structures are usually described: n using algebraic notation n = means “is composed of” n + means “and” n { } indicate repetitive elements n [ ] represent an either/or situation n ( ) represent an optional element

3/5/2009Computer systems11 Data Structure Syntax n Data Structure (table) – collection of structural records n Structural Record (row) – collection of component elements n component elements (column) – collection of characters

3/5/2009Computer systems12 Data Structure Example n Customer Name = – First Name + – (Middle Initial) + – Last Name n Method of Payment = – [Check | Charge | Money Order] n Credit Card Type = – [American Express | MasterCard | Visa]

3/5/2009Computer systems13 Logical Data Structures The data elements used by users such as – name – address – balance due – telephone Logical design stage – reflect user’s view of the system

3/5/2009Computer systems14 Physical Data Structure Physical data structure includes additional elements used by the system – Key fields – codes identify the status of master records – transaction codes n used to identify types of records – Repeating group entries count – Limits on repeated group – A password for security

3/5/2009Computer systems15 Data Elements Each data element should be defined once 1. Element ID 2. Name of element 3. Aliases 4. A short description 5. Base or derived element 6. length 7. data type 8. I/O format 9. validation criteria for accuracy 10. default value 11. additional comment or remarks area

3/5/2009Computer systems16 Data Stores Data store description form n data store ID n name n alias for the table n short description n file type: computer or manual n format : database, indexed, sequential, or direct n maximum and average number of records n file or data set name n comment

3/5/2009Computer systems17 Creating Data Dictionary n Analyzing Input and Output n Developing Data Store

3/5/2009Computer systems18 I/O Analysis Form The form may contains n Descriptive name n User contact n Input or output file type n Format of data flow – report – screen – undetermined n Elements – sequence – base or derived data – etc.

3/5/2009Computer systems19 Data Flow / Data Store n Data flow – data in motion n data store – data at rest

3/5/2009Computer systems20 Data Flow Example Employee Paycheck Hours worked 2.1 General Process BBB General Process BBB 2 D3 Employee DS Employee Record Current pay

3/5/2009Computer systems21 Data Dictionary Entries Employee Paycheck Hours worked 2.1 General Process BBB General Process BBB 2 D3 Employee DS Employee Record Current pay amount Hours Worked = Employee ID + Hours Employee Record = Employee ID + Personal Information + Wage Information Employee paycheck = Employee ID + Employee Name + Address + Current pay amount + Pay Date

3/5/2009Computer systems22 Using the Data Dictionary may be used to create n screens n reports n forms

3/5/2009Computer systems23 Extensible Markup Language n Similar to HTML n HTML – formatting document n XML – data sharing between different systems – a way to n define, n sort, n filter, and n translate data into a universal data language