ANNEXED ANNEXED A Simbología and procedure to make Data flow diagrams In order to diagramar in flow of the data we left from the base of the fundamental concepts of the Systems: a) Data exist generally, that come from External Beings to the same one. An External Being consists of a System or Subsystem that provides information with entrance but that not this included/understood in system to study. Nótese that the model talks about information, independently of the support of the same one. The information can be provided in several supports. A information support consists of the average physicist in who the information is registered. It can as much be a paper form as a diskette, CD - ROM, and - mail etc. b) Exists generally data that are generated like logout. These data can be entered as well of another external being. c) Processes within the system Exist. A process is the joint action or of actions that allow to turn or to transform the input datas into the output datas of the System. d) the System by definition can be disturbed in called sectors subsystems. A subsystem consists of a component of a greater system, diagramado under its same rules. { Gane and Sarsons 1983 } Sintetizan in its work a methodology for the study of the system using four basic symbols a) External being: A rectangular figure is used b) Process: A circle is used c) File: A rectangle without one of the lateral edges is used d) Flow of Information: An arrow is used The grafica panel A1.1 the basic simbología PANEL BASIC A1.1 SIMBOLOGÍA FOR THE LAYOUT OF SYSTEMS The generic interpretation of a data flow diagram is in the PANEL A1.2 PANEL A1.2 GENERIC INTERPRETATION OF A DATA FLOW DIAGRAM This diagram it is come off, then, that the system object is nourished of data of two different external beings, which serves to be able to make three processes after which output datas for other two external beings are obtained. Let us see a concrete example. Example: To construct the data flow diagram of the following subsystem: " Verification of Invoiced Amounts: " The suppliers send the invoices to the being, which are verified stops: a) To state the base of suppliers the data of the same one and to write down changes such as modifications of the address, trade name, high of a new supplier etc. The base of suppliers with the emanated new developments of this process is modified b) the invoices are checked mathematically to state the calculations so that the amounts are equal to the unitary prices multiplied by the amounts (mas/menos the discounts) We have then that: AMOUNT BY ITEM = UNITARY PRICE * AMOUNT As well check that the total amount is the sum of the amounts by ítems (before determining the discounts) EXTREME TOTAL AMOUNT = OF AMOUNTS BY ÍTEMS c) the data in the data base of invoicing with the correct amounts are added d) To order of the Head of the Sector the data of the invoicing table are processed to be able to obtain a totalized listing of invoicing per day and supplier The panel A1.3 illustrates the resolution of this diagram PANEL A1.3 Verification of Invoiced Amounts Aim of the Annexed A Previous Pagina Following Pagina
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