Unit 6 - Software Design and Development LESSON 10 DESIGN TOOLS, INPUTS, OUTPUTS, STORYBOARDS

Transcription

1 Unit 6 - Software Design and Development LESSON 10 DESIGN TOOLS, INPUTS, OUTPUTS, STORYBOARDS

2 Previously Key features of programming languages Software Development Lifecycle Using tools to demonstrate software design Inputs and outputs GUI design with storyboards Design constraints. Tools. Data flow diagrams. Structure diagrams. Entity relationship models

3 What is covered in this session Inputs and outputs Tools. Structure diagrams. Data flow diagrams. also need to document: the development platform and version, the language used version of the solution

4 Data flow diagrams (DFD) Used to identify and understand how data 1. flows into (input) 2. flows out of (output) a system.

5 Data flow diagrams Model the main outputs and sources of data in the scenario 1. Draw the system box 2. Name the system. 3. Identify the information that is flowing to the system from the system.

6 Data flow diagrams Food ordering system Context Diagram (level 0)

7 Context Diagram First DFD in every business process Shows the context into which the business process fits Shows the overall business process as just one process (process 0) Shows all the external entities that receive information from or contribute information to the system.

8 Level 1 Diagram Shows all the major processes that comprise the overall system the internal components of process 0 Shows how the major processes are interrelated by data flows Shows external entities and the major processes with which they interact Adds data stores

9 Level 1 Diagram

10 Level 1 Diagram three processes, four external entities two data stores.

11 Level 1 Diagram Based on the diagram, we know that a Customer can place an Order. The Order Food process receives the Order, forwards it to the Kitchen, store it in the Order data store, and store the updated Inventory details in the Inventory data store. The process also deliver a Bill to the Customer. Manager can receive Reports through the Generate Reports process, which takes Inventory details and Orders as input from the Inventory and Order data store respectively. Manager can also initiate the Order Inventory process by providing Inventory order. The process forwards the Inventory order to the Supplier and stores the updated Inventory details in the Inventory data store.

12 Level 1+ Diagrams Generally, one level 1 diagram is created for every major process on the level 0 diagram Shows all the internal processes that comprise a single process on the level 0 diagram Shows how information moves from and to each of these processes If a parent process is decomposed into, for example, three child processes, these three child processes wholly and completely make up the parent process Level 2 Diagrams Shows all processes that comprise a single process on the level 1 diagram etc

13 Data Flow Diagrams One of the main methods available for analysing data-oriented systems. DFDs emphasize the logic underlying the system. The systems analysts can put together a graphical representation of data movement through the organization..

14 Data Flow Diagrams - advantages Four advantages over narrative explanations of data movement: Freedom from committing to the technical implementation too early. Understanding of the interrelationships of systems and subsystems. Communicating current system knowledge to users. Analysis of the proposed system.

15 DFD - Basic Symbols A double square for an external entity--a source or destination of data. An arrow for movement of data from one point to another. A rectangle with rounded corners for the occurrence of transforming process. An open-ended rectangle for a data store.

16 DFD - Basic Symbols

17 DFD Task 27 Create a Context diagram for the scenario in assignment 3. Note this diagram could form part of the next assignment. 15 minutes

18 Structure Diagrams hierarchical used to display how system will be broken into procedures Can also be used to break procedures down to show their working can show decision structures and loops

19 Data structure diagram a diagram of the conceptual data model. The basic graphic notation elements of DSDs are boxes which represent entities. The arrow symbol represents relationships. Data structure diagrams are most useful for documenting complex data entities.

20 Data structure diagram

21 Data structure diagram show module structure and calling relationships. In a multi-threaded system, each task (thread of execution) is represented as a structure chart. Large structure charts are levelled into a stack of connected diagrams. Structure charts omits the detail that is found in flow charts. still need a flow chart but of each path in the diagram.

22 Data structure diagram Task 28 Create a data structure diagram for the requirements provided in Assignment 3. Note this diagram could form part of the next assignment. 15 minutes

23 Summary DSD DFD Completed two diagrams for use in A3