WIH3001_Lecture slides_Sem2_Week 1_2024_v2.pdf

Information Systems III (WIH3001) Advanced Design Data and Process Modeling Dr Bukelwa Ngoqo E-mail : [email protected] Office number : R253 General  Welcome!  Virtual Classroom Etiquette Learning Objectives (1 of 2)  After this...

Information Systems III (WIH3001) Advanced Design Data and Process Modeling Dr Bukelwa Ngoqo E-mail : [email protected] Office number : R253 General  Welcome!  Virtual Classroom Etiquette Learning Objectives (1 of 2)  After this chapter, you will be able to: Explain data flow diagrams Draw the four basic data flow diagram symbols Explain the six guidelines used when drawing data flow diagrams Draw context diagrams Create a data dictionary Data Flow Diagrams  Systems analysts use graphical techniques to describe an information system Data flow diagram (DFD) - Uses various symbols to show how the system transforms input data into useful information - Shows how data moves through an information system but does not show program logic or processing steps  A data flow diagram (DFD) maps out the flow of information for any process or system.  Data flowcharts can range from simple, even hand-drawn process overviews, to in-depth, multi-level DFDs that dig progressively deeper into how the data is handled. Data Flow Diagram Symbols (1 of 9)  Four basic symbols represent processes, data flows, data stores, and entities FIGURE 5-1 Data flow diagram symbols, symbol names, and examples of the Gane and Sarson and Yourdon symbol sets Data Flow Diagram Symbols (2 of 9)  Process symbols Process receives input data and produces output Contains business logic that transforms the data Process name identifies a specific function In DFDs, a process symbol can be referred to as a black box Data Flow Diagram Symbols (3 of 9)  Data flow symbols Line with a single or double arrowhead FIGURE 5-3 Examples of correct combinations of data flow and process symbols Data Flow Diagram Symbols (4 of 9)  Data flow and process combinations that must be avoided Spontaneous generation Black holes Gray holes FIGURE 5-4 Examples of incorrect combinations of data flow and process symbols. APPLY INSURANCE PREMIUM has no input and is called a spontaneous generation process. CALCULATE GROSS PAY has no outputs and is called a black hole process. CALCULATE GRADE has an input that is obviously unable to produce the output. This process is called a gray hole. Data Flow Diagram Symbols (5 of 9)  Data store symbol Represent data that the system stores DFD does not show the detailed contents of a data store - Specific structure and data elements are defined in the data dictionary A data store must be connected to a process with a data flow Data Flow Diagram Symbols (6 of 9)  Entity symbol Shows how the system interfaces with the outside world DFD shows only external entities that provide data to the system or receive output - DFD entities also are called terminators because they are data origins or final destinations - Source and sink entities Data Flow Diagram Symbols (7 of 9) FIGURE 5-7 Examples of correct uses of external entities in a data flow diagram. Data Flow Diagram Symbols (8 of 9) Data Flow Diagram Symbols (8 of 9) FIGURE 5-8 Examples of incorrect uses of external entities. An external entity must be connected by a data flow to a process, and not directly to a data store or to another external entity. Data Flow Diagram Symbols (9 of 9)  Using DFD symbols FIGURE 5-9 Examples of correct and incorrect uses of data flows. Data Flow Diagram Symbols (9 of 9)  Using DFD symbols FIGURE 5-9 Examples of correct and incorrect uses of data flows. Drawing Data Flow Diagrams (1 of 2)  Graphical model is created based on fact-finding results Review guidelines for drawing DFDs Apply guidelines and create a set of DFDs DFD – Example 1 (Class Discussion) DFD – Example 2 (Class Discussion) DFD – Levels  Gane-Sarson / Yourdon notation, uses leveled diagrams, that is, a roll-up and drill-down approach where increasing levels of detail are shown on successive diagrams.  A process called functional decomposition is used to represent each process in more detailed steps/processes.  Each process in a DFD can be “exploded” to become a DFD. When this is done, decimal numbers can be used to identify the process, while maintaining the links to the “parent” or higher-level process on the parent diagram. A context diagram is the highest level. There is a detailed lower-level of DFDs as needed. DFD – Levels Drawing Data Flow Diagrams (2 of 2)  Guidelines Draw the context diagram so that it fits on one page Use the name of the information system as the process name in the context diagram Use unique names within each set of symbols Do not cross lines Provide a unique name and reference number for each process Ensure that the model is accurate, easy to understand, and meets the needs of its users Drawing a Context Diagram  First step in constructing a set of DFDs FIGURE 5-11 Context diagram DFD for an order system. Context Diagrams  A context class diagram is an information system development tool used by software developers to represent the relationship between the main product and its various subsystems or components.  A context diagram outlines how external entities interact with an internal software system.  It’s the most basic form of a data flow diagram, providing a broad view of the system and external entities in an easily digestible way.  Because of its simplicity, it’s sometimes called a level 0 data flow diagram.  A system context diagram is typically drawn with the system in the middle (either in a circle or a square). Context Diagram – Example 1 Context Diagram – Example 2 Data Dictionary Data Dictionary (1 of 11)  Central storehouse of information about a system’s data An analyst uses the data dictionary to collect, document, and organize specific facts about a system Defines and describes all data elements and meaningful combinations of data elements Data Dictionary (2 of 11)  Data element (i.e., data item or field) Smallest piece of data that has meaning within an information system Combined into records (i.e., data structures) - Record: meaningful combination of related data elements that is included in a data flow or retained in a data store Data Dictionary (3 of 11)  Using CASE tools for documentation More complex the system, more difficult it is to maintain full and accurate documentation Modern CASE tools simplify the task A CASE repository ensures data consistency Data Dictionary (4 of 11)  Documenting the data elements Every data element in the data dictionary should be documented Objective: provide clear, comprehensive information about the data and processes that make up a system Data Dictionary (5 of 11)  Recorded and described attributes Data element name and label Alias Type and length Default value Acceptable values Source Security Responsible user(s) Description and comments Data Dictionary (6 of 11)  Documenting the data flows Data flow name or label Description Alternate name(s) Origin Destination Record Volume and frequency Data Dictionary (7 of 11)  Documenting the data stores Data store name or label Description Alternate name(s) Attributes Volume and frequency Data Dictionary (8 of 11)  Documenting the processes Process name or label Description Process number Process description Data Dictionary (9 of 11)  Documenting the entities Entity name Description Alternate name(s) Input data flows Output data flows Data Dictionary (10 of 11)  Documenting the records Record or data structure name Definition or description Alternate name(s) Attributes Data Dictionary (11 of 11)  Data dictionary reports Alphabetized list of all data elements Report describing each data element and indicating the user or department Report of all data flows and data stores that use a particular data element Detailed reports showing all characteristics of data elements, records, data flows, processes, or any other selected item stored in the data Activity 1 – Create DB  DB Name: WIH3002DB  Create the following table: Persons Artist First Name Last Name Address City ID Activity 1 – Create DB  DB Name: WIH3002DB  Create the following table: MusicCatalogue Barcod Song Album Year Artist ID e SQL – Table(s) CREATE TABLEtable_name( column1 datatype, column2 datatype, column3 datatype,.... ); Answer 1: Create Database WIH3002DB; CREATE TABLE Persons ( ArtistID int, LastName varchar(255), FirstName varchar(255), ResAddress varchar(255), City varchar(255) ); Answer 1: Use Database WIH3002DB; CREATE TABLE MusicCatalogue ( ArtistID int, Barcode varchar(255), Song varchar(255), Album varchar(255), Year date ); Activity 2 – Insert Values  Insert into Table: Persons Artist First Name Last Name Address City ID 1 Sam Smith 12 Lovesong New York Lane 2 Whitney Houston 100 RandB Bloemfontein Street Answer 2: INSERT INTO WIH3002DB.dbo.Persons (ArtistID,LastName,FirstName,ResAddress,City) VALUES ( 1,'Smith','Sam','12 Lovesong Lane','New York'), ( 2,'Houston','Whitney','100 RandB Street','Bloemfontein') ; Activity 1 – Create DB  Insert into table: MusicCatalogue Barcod Song Album Year Artist ID e 0000450 Too good at The thrill of it All 2017 1 goodbyes 0000451 I have Whitney 1987 2 nothing 0000459 Where you Whitney 1987 2 are 0000600 I have The Bodyguard 1992 2 nothing Answer 2: INSERT INTO WIH3002DB.dbo.MusicCatalogue (Barcode,Song,Album,Year,ArtistId) VALUES ('0000450', 'Too good at goodbyes','The thrill of it All', '2017',1), ('0000451', 'I have nothing','Whitney', '1987', 2), ('0000459', 'Where you are','Whitney', '1987', 2), ('0000600', 'I have nothing','The Bodyguard','1987', 2) ; Activity 3 - Query  Select(display) from the database the name of the artist (and the name of the song(s)) who released a song(s) in 1987. Database Operations  Defining data structure  Define Authorisations  Define integrity conditions  Define transactions  Define views Relational Integrity Constraints  Domain Constraints  Key Constraints  Referential Integrity Constraints Any Qs?