Al Khawarizmi International College, Al Ain , U.A.E

1. Al Khawarizmi International College, Al Ain , U.A.E Software Development Module Code: CST 240 Chapter 4: Software Design Lecturer:Karamath Ateeq

2. Al Khawarizmi International College, Abu Dhabi, U.A.E Outline Software Design Approaches: • Function –Oriented design • Methodology: SSADM • Major Tools: DFD, ER Diagram • Object –Oriented Design • Methodology: OOP-Object Modeling using UML Chapter 4: Software Design

3. Al Khawarizmi International College, Abu Dhabi, U.A.E Features of function-Oriented Design: 1. A system is viewed as something that performs a set of functions. Starting from high level, each function is successively refined into more detailed functions. Eg: create-new-library consists of the following sub functions: (1) assign-membership –number (2) create-member-record (3)Print-bill 2. The system state is centralized and shared among different functions Eg: Data such as member-records is shared among (1)create-new-member (2)delete-member (3) update-member-record Chapter 4: Software Design

4. Al Khawarizmi International College, Abu Dhabi, U.A.E • Object –Oriented Vs Function –Oriented Design: • Unlike Function –Oriented Designmethods ,in OOD, the basic abstractions are not real –world functions like sort, display etc but real- worldentities such as employee ,picture ,machine ,radar system etc. • In OOD, state information is not represented in a centralized shared memory but is distributed among the objects of the system. • Function –Oriented techniques, such as SA/SD, group functions together as if they constitute a high level function . On the other hand Object –Oriented techniques group the functions together on the basis of the data they operate on Chapter 4: Software Design

5. Al Khawarizmi International College, Abu Dhabi, U.A.E SSADM- Structured System Analysis and Design Method. SSADM uses a combination of three techniques: • Logical Data Modeling- The processing of identifying, modeling and documenting the data. The data is separated into entities and relationships between the entities. • Data Flow Modeling- The processing of identifying, modeling and documenting how the data moves around the system. It examines the processes, data stores, external entities and data flows. • Entity Behavior Modeling-The processing of identifying, modeling and documenting the events that affect each entity and the sequence in which these events occur. Chapter 4: Software Design

6. Al Khawarizmi International College, Abu Dhabi, U.A.E SSADM application development projects are divided into five modules: • Feasibility study. • Requirements Analysis. • Requirements Specification. • Logical System Specification. • Physical Design. Chapter 4: Software Design

7. Al Khawarizmi International College, Abu Dhabi, U.A.E Advantages of using SSADM : Unlike rapid application development , which conducts steps in parallel , SSADM builds each step on the work that was prescribed in the previous step ,with no deviation from the model. It has a control over the project and has the ability to develop better quality systems. Chapter 4: Software Design

8. Al Khawarizmi International College, Abu Dhabi, U.A.E Context Analysis Diagram • The context diagram represents the entire system under investigation. • The components of a context diagram are • Process :Shows the main process of the system. • External entities : External Entity is a source or destination of the data, e.g a person, supplier, department, or another system. • Data flows: The data flow shows the flow of data from an external entity to the process and vice-versa. Chapter 4: Software Design

9. Al Khawarizmi International College, Abu Dhabi, U.A.E Data-flow Diagram • Data-flow diagrams illustrate how data flows through a system and how the output is derived from the input through a sequence of functional transformations. Chapter 4: Software Design

10. Al Khawarizmi International College, Abu Dhabi, U.A.E DFD Components The components are • any external entity that interact with the system, • the system processes, • the datastored by these process, • and the data flows in the system. Chapter 4: Software Design

11. Al Khawarizmi International College, Abu Dhabi, U.A.E DFD Symbols • Data flow diagrams use a number of symbols to represent systems components. Several different versions of symbols are used to construct DFD's. Two major versions are: • Yourdan /Demarco • Gane/Sarson Chapter 4: Software Design

12. Al Khawarizmi International College, Abu Dhabi, U.A.E DFD Symbols Chapter 4: Software Design

13. Al Khawarizmi International College, Abu Dhabi, U.A.E External entity • External entity is a source or destination of a data flow which is outside the area of study. • Represents organizations, agents, or people, outside the system under study. • Duplicate external entity is shown as Customer Customer Chapter 4: Software Design

14. Al Khawarizmi International College, Abu Dhabi U.A.E Process • Processes represent the transformation of data as it flows thorough the system. • Each process symbol has its unique identifying number (such as 1.0,2.0, 2.1.2 and so on) • Process symbol should also be labeled with purpose or type of process to occur. The label should be a unique and expressing a strong statement of action on an object such as update inventory, create order etc Chapter 4: Software Design

15. Al Khawarizmi International College, Abu Dhabi, U.A.E Identification 4.0 Description of the function VERIFY ORDER Location (opt.) Purchase dept Process • The location specification at the bottom of the symbol is optional. It is used strictly as documentation, to show either where the process occurs or who is responsible for it. Chapter 4: Software Design

16. Al Khawarizmi International College, Abu Dhabi, U.A.E ID Description D1 Customer data Data Store • Data Store is a repository where the data is stored. • It can be a data base or file on a tape or disk, or it can be a manual medium such as filing cabinet. Chapter 4: Software Design

17. Al Khawarizmi International College, Abu Dhabi, U.A.E 1.0 Customer Verify order Customer - order Data Flow • Data flow show the flow of information from an entity to a process or a process to a data store or vice-versa. • Any one end of a data flow must be connected to a process. Chapter 4: Software Design

18. Do’s and Don'ts Chapter 4: Software Design

19. Al Khawarizmi International College, Abu Dhabi, U.A.E DFD Levels • Level 0 DFD : The level 0 DFD shows only the main processes of the system. Ideally 7-9 processes can be shown in Level 0 DFD. Processes are numbered as 1.0,2.0,3.0 and so forth. • Level 1DFD :The Level 1 DFD is created to explode any one process of the level 0 DFD.Level 1 DFD, for process 1 in level 0 DFD, will be numbered as 1.1,1.2,1.3 etc. Chapter 4: Software Design

20. Al Khawarizmi International College, Abu Dhabi U.A.E DFD Types There are two types of DFDs: • Logical DFD: • Physical DFD: Chapter 4: Software Design

21. Al Khawarizmi International College, Abu Dhabi, U.A.E Logical vs Physical DFD Chapter 4: Software Design

22. Al Khawarizmi International College, Abu Dhabi, U.A.E Logical DFD guidelines Data flows: • Physical DFDs corresponds to things like business forms, documents, reports, terminal displays, spoken communication such as phone calls etc. But logical data flows are implementation independent. • A logical DFD represents the minimum, essential data necessary needed by the process that receives the data flow. Chapter 4: Software Design

23. Al Khawarizmi International College, Abu Dhabi, U.A.E Logical DFD Guidelines Data flows: • Logical dataflow names should be descriptive adjectives and nouns. • Data flow names should be singular and not plural. Chapter 4: Software Design

24. Al Khawarizmi International College, Abu Dhabi, U.A.E Logical DFD Guidelines Logical Process: • Logical processes depicts what work or action has been performed on incoming data flows to produce outgoing data flows and not who or what is doing that work or activity. • Examples: • Credit customer account • Update inventory • Verify account. Chapter 4: Software Design

25. Al Khawarizmi International College, Abu Dhabi, U.A.E Logical DFD Guidelines Logical Data Store: • Logical data store are very different from the physical data store. • Physical data store corresponds to implementations such as databases, files, file cabinets, log sheets, books etc. • In contrast , the logical data stores represent the businesspeople, objects and events about which we need to store data. Chapter 4: Software Design

26. Al Khawarizmi International College, Abu Dhabi, U.A.E Practical • Draw CAD and DFD for the given case study. • The operation theater of Al Noor Hospital requires a computerized system to maintain the details of the patient who undergo operations. A patient comes to the ward with an admission note from a doctor. The patient is admitted in a ward of the hospital for an operation. Before admitting the patient the personal details of the patient is obtained and an admission file is open and an operation note is given to the patient. The information of each operation conducted in the hospital has to be maintained separately. Al Noor hospital gives special discount to some patients according to their policy. The policy should include details of discount given. On a daily basis a report of patients undergoing an operation the next day should be generated by the system. This report is given to the management. Another report should be generated for the doctor that gives details of the number of operations he has the next day. After the operation, when a patient has to be discharged a patient-discharge note is given to the patient. • Draw a Context diagram and Data Flow diagram or the given case study. Chapter 4: Software Design

27. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Dictionary • A data dictionary lists all data items appearing in the DFD model of a system. • The data items listed include all data flows and the contents of all data stores appearing on all DFD’s in the DFD model of a system. • The data flows on the context diagram can be used as a start of the data dictionary Chapter 4: Software Design

28. Al Khawarizmi International College, Abu Dhabi, U.A.E Benefits of Data Dictionary A data dictionary plays a very important role in any software development process because of the following reasons: • It provides a standard terminology for all relevant data for use by all engineers working in the same project. • It helps the analyst to know the component elements of a data structure. • Data dictionary also serves as basis for creating systems database. Chapter 4: Software Design

29. Al Khawarizmi International College, Abu Dhabi, U.A.E Components of Data Dictionary • Data Flow: Data flow is usually the first component to be defined. • Data Store: Data’s are stored here. • Data element: The most basic piece of data that can’t be broken into more detailed unit is called data element. • Data structures: Combinations of data elements make up data structures i.e. a meaningful set of data elements. Chapter 4: Software Design

30. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Dictionary Types • Logical data dictionary:It needs only data elements name like the description of the item, its number, color, size, price, quantities etc., • Physical data dictionary:It might include data element names along with some characteristics of those elements e.g. field size, checks/controls/validation, data store/s using those elements etc. Chapter 4: Software Design

31. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Dictionary Rules • The terms used for data structures should be capital • Name having multiple words are hyphenated(-) e.g ITEM-DESC • Assigned names should be straight forward and user oriented • There should be a name for each data flow, data store, data structure, data element • No two data flows should have the same name • A data flow should not have more than one name and aliases (nick names) must be discouraged Chapter 4: Software Design

32. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Flow Example Note: Data Flow types can be Form, Note, Paper list, Letter etc Chapter 4: Software Design

33. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Store • When data flow elements are grouped to form a structural record, a data store is created for each unique structured record. • One data store may contain several data structures. Chapter 4: Software Design

34. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Store Examples Chapter 4: Software Design

35. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Structure Data Structure Symbols • = means “equivalent” • + means “and” • {} means “repeating data element” • [|] means “either one data element or another” • ( ) means “optional data element” Chapter 4: Software Design

36. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Structure example • CUSTOMER = customer_id + CUSTOMER_NAME+ ADDRESS+ phone CUSTOMER_NAME= first_name + (middle_name) + last_name ADDRESS = (street) + p.o.box+ city Chapter 4: Software Design

37. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Structure example • PAYMENT = payment_id + payment_date+customer_id + total_amount + payment_mode + [credit_card_no | check_number] + { item_id + item_name +qty + unit_price +amount} Chapter 4: Software Design

38. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Element • Data element is the smallest unit which cannot be divided further. • Each data element must be defined once in data dictionary. • Input/output format symbols: X - May enter or display any character 9 - Enter or display only numbers , - insert comma into a numeric display - - separator Chapter 4: Software Design

39. Al Khawarizmi International College, Abu Dhabi, U.A.E Data Element Examples Chapter 4: Software Design

40. Al Khawarizmi International College, Abu Dhabi, U.A.E E-R Diagram • Entity Relationship Diagram shows the relationship between the tables in a database. • The relationship can be • One- to – One • One- to many • Many -to -many Chapter 4: Software Design

41. Al Khawarizmi International College, Abu Dhabi, U.A.E Chapter 4: Software Design

42. Al Khawarizmi International College, Abu Dhabi, U.A.E Introduction to UML • UML stands for Unified Modelling Language • UML is emerging as a standard modelling language Object Oriented Modelling. • It is useful for graphically depicting object-oriented analysis and design models Chapter 4: Software Design

43. Al Khawarizmi International College, Abu Dhabi, U.A.E UML • UML allows to represent multiple views of a system using a variety of graphical diagrams: • Use-Case Diagram • Class Diagram • State Diagram • Sequence Diagram • Collaboration Diagram Chapter 4: Software Design

44. Al Khawarizmi International College, Abu Dhabi, U.A.E UML • Use Case • A use-case model consists of actors and use cases. • It helps us to get the functional requirement of the system. • Use case gives a complete sequence of related actions initiated by an actor to accomplish a specific goal. Chapter 4: Software Design

45. Al Khawarizmi International College, Abu Dhabi, U.A.E UML • Class Diagram: It shows the main concepts and techniques in object modelling. • State Diagram: A state diagram depicts the various state transitions or changes an object can experience during its lifetime. • Interaction between use cases is shown using two diagrams called • Sequence Diagram • Collaboration Diagram Chapter 4: Software Design

46. Al Khawarizmi International College, Abu Dhabi, U.A.E Lending service Library User administration Library Staff Catalogue services Supplier Use-case Diagram User Chapter 4: Software Design

47. Al Khawarizmi International College, Abu Dhabi, U.A.E Class Diagram Chapter 4: Software Design

48. Al Khawarizmi International College, Abu Dhabi , U.A.E State Diagram Chapter 4: Software Design