TCS2411 Software Engineering1 Functional and Behavioural Modeling “What is the software supposed to do?”

TCS2411 Software Engineering2 Lecture Objectives zTo illustrate the modeling of functional and behavioural characteristics of the problem domain zTo describe the elements of data flow diagrams and the associated rules for drawing them correctly zTo describe the elements and usage of state transition diagrams

TCS2411 Software Engineering3 Functional Modeling zIn understanding the requirements of the software, the functions required by the customer will be identified zAll the functions process information in some way in the system zBasically input  process  output zRepresentation of how information is transformed

TCS2411 Software Engineering4 Data Flow Diagram (DFD) zGraphical representation of functional modeling zIn analysis, provide representation of information flow in existing and required system zIn design, the DFDs can be decomposed into lower level processes (sub-systems) for implementation

TCS2411 Software Engineering5 Context Diagram CustomerKitchen Restaurant Manager Food Ordering System Food Order Customer Order Receipt Management Reports

TCS2411 Software Engineering6 Level-1 DFD CustomerKitchen Restaurant Manager 1. Process Customer Order Food Order Customer Order Receipt Management Reports 2. Update Goods Sold 3. Update Inventory 4. Produce Management Reports Goods Sold Inventory Goods Sold Inventory Data Inventory Record Goods Sold Record Daily Goods Sold Amounts Daily Inventory Depletion Amounts

TCS2411 Software Engineering7 External Entity zA producer or consumer of information that resides outside the bounds of the system to be modeled zSource - producer of information zSink - consumer of information zExamples: CustomerSupplierManagement

TCS2411 Software Engineering8 Process zA transformer of information (a function) that resides within the bounds of the system to be modeled zExamples: 1.Process New Member 2. Student Registration 2.1 Accept Registration Details

TCS2411 Software Engineering9 Data Flow zData object that flows in the system; the arrowhead indicates the direction of data flow new student record student record

TCS2411 Software Engineering10 Data Store zA repository of data that is to be stored for use by one or more processes zMay be as simple as a buffer or queue or as sophisticated as a relational database zExamples: StudentsInventoryCourses

TCS2411 Software Engineering11 DFD Rules zProcess yNo process can have only outputs. yNo process can have only inputs. yA process has a verb label.

TCS2411 Software Engineering12 DFD Rules zData Store yData cannot move directly from one data store to another data store. yData cannot move directly from an outside source to a data store. yData cannot move directly to an outside sink from a data store. yA data store has a noun phrase label.

TCS2411 Software Engineering13 DFD Rules zSource/Sink yData cannot move directly from a source to a sink. It must be moved by a process if the data are of any concern to our system. yA source/sink has a noun phrase label.

TCS2411 Software Engineering14 DFD Rules zData Flow yA data flow has only one direction of flow between symbols. yA fork in data flow means that exactly the same data goes from a common location to two or more processes/stores/sources/sinks. yA join in a data flow means that exactly the same data comes from any two or more processes/stores/sources/sinks.

TCS2411 Software Engineering15 DFD Rules zData Flow (continued) yA data flow cannot go directly back to the same process it leaves. yA data flow to a data store means update. yA data flow from a data store means retrieve or use. yA data flow has a noun phrase label. More than one data flow noun phrase can appear on a single arrow.

TCS2411 Software Engineering16 DFD Characteristics zCan be used to model physical or logical, current or new systems zDoes not represent procedural or time- related processes zRevisions to the same DFD are done to improve model based on understanding zDecision to stop iterative decomposition may be difficult

TCS2411 Software Engineering17 Behavioural Modeling Outside world Application events behavior

TCS2411 Software Engineering18 Behavioural Modeling zRepresentation of how the system changes and the events that cause the changes to happen zAlso represent actions that may be taken as consequences of events zGraphically drawn as state transition diagram

TCS2411 Software Engineering19 State Transition Diagram (STD) Notation State New state Event causing transition Action that occurs

TCS2411 Software Engineering20 State Transition Diagram (STD) Idle RingingConnected incoming call button pressed initiate answer announce complete answered announce message hangup

TCS2411 Software Engineering21 State Transition Diagram Elements zState - any observable mode of behaviour yrepresented as a node in STD zState transition - change of one state to another caused by an event yrepresented as labeled arrow in STD ylabel is the event causing the transition zEvent - external or internal occurrence that has an effect on the system zAction - process taken as response to event

TCS2411 Software Engineering22 References z“Software Engineering: A Practitioner’s Approach” 5th Ed. by Roger S. Pressman, Mc-Graw-Hill, 2001 z“Software Engineering” by Ian Sommerville, Addison-Wesley, 2001 z“Modern Systems Analysis and Design” by Jeffrey A. Hoffer, Joey F. George & Joseph S. Valacich, Benjamin/Cummings, 1996