06 Data Flow Diagrams - Exploding And Franchise Colleges 06 Data Flow Diagrams - Exploding By MANSHA NAWAZ Section 06 DFD - Exploding

Learning Aims Aim Objectives to be able to explode a process on a top-level DFD Objectives to distinguish primitive/non primitive processes to identify appropriate sub-processes to identify local data stores to construct the exploded DFD consistent with the parent DFD Section 06 DFD - Exploding

Lecture Outline selecting processes for exploding initial inputs and outputs identifying sub-processes local data stores diagram construction consistency checking diagram hierarchy Section 06 DFD - Exploding

Checking Processes on the DFD check each process, can it be broken down into meaningful sub-processes? no a functional primitive do not explode yes explode the process Q 3 enter order 1 check stock þ Section 06 DFD - Exploding

Inputs & Outputs to Explosions each exploded process has its own inputs and outputs the data flows into the process must all appear as inputs to the exploded process the data flows out of the process must all appear as outputs from the exploded process Section 06 DFD - Exploding

Modelling Sub-processes the task is to identify all the sub-processes that must take place to achieve the purpose of the parent process start by identifying the normal sequence of events list the processes identify the error or abnormal events add to the process list Section 06 DFD - Exploding

Local Data Stores it may become apparent that a new data store is required if only the sub-processes interface with it then add it to the exploded diagram if other processes use it, add to the top level if a data store on the top level DFD only interfaces with one process remove it and place inside the exploded process Section 06 DFD - Exploding

Diagram Construction the exploded process is represented by a large frame, named and numbered on the left outside are placed the inputs on the right outside are placed the outputs sub-processes & local data stores are placed inside the frame Section 06 DFD - Exploding

Contd. add the processes connecting them to the in/outputs numbering the processes n.1, n.2 etc where n is the number of the parent numbering the data stores continue the sequence from the top level make sure all inputs & outputs are connected to the sub-processes Section 06 DFD - Exploding

Consistency Checking check numbering correct check no name clashes check number of inputs and outputs are at least as many as those on the top level if there are more check they are logically the same flow duplication and splitting is possible Section 06 DFD - Exploding

Diagram Hierarchy it is possible to explode the processes in an exploded diagram this leads to a hierarchy of levelled DFDs Section 06 DFD - Exploding

Development : Low-Level DFD Low-Level Data Flow Diagram (LL-DFD) For each process Low-Level DFD description Low-Level DFD Diagram Top-Level Data Flow Diagram (TL-DFD) Amend your diagrams and supporting text after consistency checking with the low-level DFD’s. Top-Level DFD description Top-Level DFD Diagram Context Diagram (CD-DFD) Context Diagram description Context Diagram Section 06 DFD - Exploding

Document : Analysis Specification Terms Of Reference lecture 02 Context Diagram lecture 03 Top-Level Data Flow Diagram lecture 04 Top-Level DFD Support Text lecture 05 Top-Level DFD lecture 06 Data Flow Fragments Low-Level Data Flow Diagrams lecture 06 lecture 07 For each Top-Level process Low-Level DFD Support Text Low-Level DFD Section 06 DFD - Exploding

Summary & Self Study Summary check processes capture in/outputs check local data stores build DFD check consistent levelled hierarchy Self Study review the lecture complete 6a from the workbook can you achieve the objectives set out in slide 2? Section 06 DFD - Exploding

… see what you can utilise from the following guides Further Reading There are many ways to develop a proposed computer system model … see what you can utilise from the following guides Guide to documenting DFDs using Toy Sales Order Example Toy Sales Ordering System Guide to modelling multilayered systems DFD Review 1 Guide to modelling basic systems DFD Review 2 Common Functions, Features, Events and Sub-Events SOP Common Functions, Features, Events and Sub-Events from PowerQuotes Case Study powerquote Sample DFD Models Ascent Solutions http://outranet.scm.tees.ac.uk/users/u0018257/SDV/SDevWk11.doc Section 06 DFD - Exploding

Further Reading Notes from Annette Marshall http://outranet.scm.tees.ac.uk/users/u0018257/SDV/SDevWk3.doc http://outranet.scm.tees.ac.uk/users/u0018257/SDV/SDevWk4.doc Section 06 DFD - Exploding