[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-seo-657612-105":3,"detail-sidebar-cat-0-en-105":80,"doc-detail-657612-en":130},{"code":4,"msg":5,"data":6},0,"ok",{"site_id":7,"language":8,"slug":9,"title":10,"keywords":11,"description":12,"schema_data":13,"social_meta":73,"head_meta":75,"extra_data":77,"updated_unix":79},105,"en","data-flow-diagrams-dfds-introduction-to-principles-notations-and-levels","Data Flow Diagrams (DFDs) - Introduction to Principles, Notations, and Levels","","Data Flow Diagrams (DFDs) are introduced as a structured, diagrammatic modeling technique for analyzing and building information systems by showing functions and how data flows into, out of, and within the system. The document explains DFDs alongside Logical Data Structure modeling (LDSs) and Entity Life Histories (ELHs), then covers DFD principles, context diagrams and decomposition, the top (1st level) DFD, and core notation concepts including process, data flow, and general flow rules.",{"@graph":14,"@context":72},[15,34,55],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/technology/","Technology",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/data-flow-diagrams-dfds-introduction-to-principles-notations-and-levels/657612/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/data-flow-diagrams-dfds-introduction-to-principles-notations-and-levels/657612.png","ImageObject",300,407,{"name":42,"@type":43},"Rainbow Cat","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-10-29","2026-10-26",true,{"@type":52,"interactionType":53,"userInteractionCount":33},"InteractionCounter",{"@type":54},"ViewAction",{"@type":56,"mainEntity":57},"FAQPage",[58,64,68],{"name":59,"@type":60,"acceptedAnswer":61},"What are the three main modeling techniques discussed in the document?","Question",{"text":62,"@type":63},"The document lists Data Flow Diagramming (DFDs), Logical Data Structure modeling (LDSs), and Entity Life Histories (ELHs) as the three most important techniques used to analyze and build information systems.","Answer",{"name":65,"@type":60,"acceptedAnswer":66},"How do DFDs help describe a target system in SSADM?",{"text":67,"@type":63},"In SSADM, DFDs answer data-oriented questions such as what processing is done, when, how, where, by whom, and what data is needed by whom and for what.",{"name":69,"@type":60,"acceptedAnswer":70},"What are the key general data flow rules for DFDs?",{"text":71,"@type":63},"Rules include that entities act as sources or sinks, data flows from entities into processes, data to entities comes from processes, processes and data stores must have both inputs and outputs, and inputs/outputs for data stores must connect only with processes.","https://schema.org",{"og:url":32,"og:type":74,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":76,"canonical":32},"index,follow",{"doc_id":78,"site_id":7},657612,1793111798,{"code":4,"msg":81,"data":82},"success",[83,87,91,95,100,104,109,114,119,122,126],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":84,"show_sort_weight":85,"slug":86},"Story & Novel",90,"story-novel",{"id":26,"doc_module":4,"doc_module_name":25,"category_name":88,"show_sort_weight":89,"slug":90},"Literature",80,"literature",{"id":33,"doc_module":4,"doc_module_name":25,"category_name":92,"show_sort_weight":93,"slug":94},"Exam",70,"exam",{"id":96,"doc_module":4,"doc_module_name":25,"category_name":97,"show_sort_weight":98,"slug":99},5,"Comic",60,"comic",{"id":101,"doc_module":4,"doc_module_name":25,"category_name":29,"show_sort_weight":102,"slug":103},6,50,"technology",{"id":105,"doc_module":4,"doc_module_name":25,"category_name":106,"show_sort_weight":107,"slug":108},7,"Healthcare",40,"healthcare",{"id":110,"doc_module":4,"doc_module_name":25,"category_name":111,"show_sort_weight":112,"slug":113},8,"Research & Report",30,"research-report",{"id":115,"doc_module":4,"doc_module_name":25,"category_name":116,"show_sort_weight":117,"slug":118},9,"Religion & Spirituality",20,"religion-spirituality",{"id":117,"doc_module":4,"doc_module_name":25,"category_name":120,"show_sort_weight":117,"slug":121},"World Cup","world-cup",{"id":123,"doc_module":4,"doc_module_name":25,"category_name":124,"show_sort_weight":123,"slug":125},10,"Lifestyle","lifestyle",{"id":127,"doc_module":4,"doc_module_name":25,"category_name":128,"show_sort_weight":96,"slug":129},19,"General","general",{"code":4,"msg":81,"data":131},{"doc_id":78,"user_id":132,"nickname":42,"user_avatar":133,"doc_module":4,"category_id":101,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":33,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":110,"language":139,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":12,"update_tm":143,"read_time":117},962090769181,"https://ap-avatar.wpscdn.com/davatar_6f874abed73319feea01a86fa6f0fab8","Data Flow Diagram  \nIntroduction  \nThe three most important modeling techniques used in analysing and building information systems are: Data Flow Diagramming (DFDs), Logical Data Structure modelling (LDSs), and Entity Life Histories (ELHs)  \nData Flow Diagrams (DFDs) model events andprocesses(i.e. activities which transform data) within a system. DFDs examine how data flows into, out of, and within the system. Logical Data Structures (LDSs) represent a system's information and data in another way. LDSs map the underlying data structures as entity types, entity attributes, and the relationships between the entities  \nEntity Life Histories (ELHs) describe the changes which happen to 'things' (data) within the system.  \nThese three techniques are common to many methodologies and are widely used in system analysis. Notation and graphics style may vary across methodologies, but the underlying principles are generally the same.  \nIn SSADM (Structured Systems Analysis and Design Methodology) -which has for a number of years been widely used in the UK-systems analysts and modelers use the above techniques to build up three, inter-related, views of the target system, which are cross-checked for consistency.  \nData Flow Diagrams (DFDs)  \n• DFD Principles  \n• Basic DFD Notations  \n•  (SSADM) DFD Notations  \n• DFD Levels  \n\" ... a structured, diagrammatic technique for showing the functions performed by a system and the data flowing into, out of, and within it ..\"  \nAnother way of looking at it is that, in SSADM, DFDs are used to answer the following data-oriented questions about a target system:  \nWhat processing is done? When? How? Where? By whom? What data is needed? By whom? for what? When?  \nHowever, we are not interested, here, in the development process in detail, only in the general modeling technique. Essentially, DFDs describe the information flows within a system.  \nDFD Principles  \n• The general principle in Data Flow Diagramming is that a system can bedecomposed into subsystems, and subsystems can be decomposed into lower level subsystems, and so on.  \n• Each subsystem represents a process or activity in which data is processed. At the lowest level, processes can no longer be decomposed.  \n• Each 'process' (and from now on, by 'process' we mean subsystem and activity) ina DFD has the characteristics of a system.  \n• Just as a system must have input and output (if it is not dead), so a process must have input and output.  \n• Data enters the system from the environment; data flows between processes within the system; and data is produced as output from the system  \nAn example:  \nThe 'Context Diagram ' is an overall, simplified, view of the target system, which contains only one process box, and the primary inputs and outputs.  \nContext diagram 2  \nContext diagram 1  \nBoth the above diagrams say the same thing. The second makes use of the possibility in SSADM of including duplicate objects. (In context diagram 2 the duplication of the Customer object is shown by the line at the left hand side. Drawing the diagram in this way emphasizes the Input-Output properties of a system. See also 'Notes' below)  \nThe Context diagram above, and the decomposition which follows, are a first attempt at describing part of a 'Home Catalogue' sales system. In the modeling process it is likely that diagrams will be reworked and amended many times-until all parties are satisfied with the resulting model. A model can usefully be described as a co-ordinated set of diagrams.  \nThe Top (1st level) DFD  \nThe Top or 1st level DFD, describes the whole of the target system. It 'bounds' the system under consideration.  \n(To simplify the diagram some notation has been left out-see 'Notes' below)  \nData Flow Diagrams show:  \n• the processes within the system  \n• the data stores (files) supporting the system's operation  \n• the information flows within the system  \n• the system boundary  \n• interactions with external entities  \nDFD Notations  \nDFDs are used in ","cbCaid45uMWPubWO","https://ap.wps.com/l/cbCaid45uMWPubWO","pdf",225163,"English","# Introduction\n# Data Flow Diagrams (DFDs)\n## DFD Principles\n## Basic DFD Notations\n## (SSADM) DFD Notations\n## DFD Levels\n# Context Diagram\n# The Top (1st level) DFD\n# DFD Notations\n## General Data Flow Rules","[{\"question\":\"What are the three main modeling techniques discussed in the document?\",\"answer\":\"The document lists Data Flow Diagramming (DFDs), Logical Data Structure modeling (LDSs), and Entity Life Histories (ELHs) as the three most important techniques used to analyze and build information systems.\"},{\"question\":\"How do DFDs help describe a target system in SSADM?\",\"answer\":\"In SSADM, DFDs answer data-oriented questions such as what processing is done, when, how, where, by whom, and what data is needed by whom and for what.\"},{\"question\":\"What are the key general data flow rules for DFDs?\",\"answer\":\"Rules include that entities act as sources or sinks, data flows from entities into processes, data to entities comes from processes, processes and data stores must have both inputs and outputs, and inputs/outputs for data stores must connect only with processes.\"}]","Data Flow Diagrams (DFDs) - Introduction to Principles, Notations, and Levels | PDF",1792985195]