Systems Analysis and Design - Chapter 5 questions and answers 2023.

a graphical way of representing how a business system should operate. It illustrates the processes or activities that are performed and how data move among them. Process model is a DFD. Contains two data components: the data flow (composed of data elements) & the data store. The purposes of these are to illustrate process model is a technique that diagrams the business processes and the data that pass among them. The DFD's focus is mostly on the processes or activities that are performed what is data flow diagramming? (DFD) models that decribe a process, without suggesting how they are conducted logical process models physical process models provide information that is needed to build the system physical process model a process is an activity or a function performed for some specific business reason. Every process must have a at least one input data flow and one output data flow. process a data flow is a single piece of data, or a logical collection of several pieces of information. data flow is a collection of data that is stored in some way. Form the starting point for the data model and are the principal link btw the process model and the data model. data store is a person, organization, org unit, or system that is external to the system but still interacts with it. (ex: customer, gov org, accounting system) Key point is that it is external to the system, but may or may not be part of the organization. external entity breaking down DFDs to individual DFDs for further detail Decomposition it shows the entire system as one process. Defines how the business process or computer system interacts with its environment. Context Diagram shows all the major high level processes of the system and how they are interrelated. A process model has one and only one level 0 DFD Level 0 Diagram ensuring that all information presented in a DFD at one level is accurately represented in the next-level DFD Balancing Each process of level 0 is decomposed into more explicit DFD called LEvel 1 Level 1 Diagrams as many processes as you have in level 0 How many level 1 diagrams should there be? the next level of decomposition- shows all the processes, data flows, and data stores that comprise a single process on the level 1 Diagram. Level 2 Diagrams when a process produce data that flows under a different circumstance Alternative Data Flows used to explain why alternative data flows are different Process discription - structured english - decision trees - decision tables What are the 3 techniques used to describe processing logic use info in use cases and requirements definition. the project team takes the use cases and rewrites the use cases, following the formal rules and syntax Creating DFDs Draw one process symbol numbered 0 add all inputs and outputs on form as data flows draw the external entities NO DATA STORES Creating Context Diagram fragment is one part of a DFD that eventually will be combined with other DFD fragments for form a DFD each use case is converted into one DFD fragement Creating DFD Fragments combine the set of DFD fragments into one diagram reads from left to right Iteration is the cornerstone of a good DFD Creatine level 0 DFD a DFD is created for each process in LEVEL 0 Level 1 DFD Syntax Errors: can be though of as grammatical errors that violate the rules of the DFD language Semantics errors: can be thought of as misunderstanding by the analyst in collecting, analyzing, and reporting information about the system Validating the DFD a formal way of representing the data that are used and created by a business system; it illustrates people, places, or things about which information is captured and how they are related to each other. In general, data models are based on interpretation, so it is important to clearly state assumptions that reflect business rules. data model A well constructed use case makes developing a data flow diagram quite straightforward. The steps outlined in a use case can be organized into logical processes on a DFD. The Major Inputs and Major Outputs listed on the use case provide a list of the sources and destinations of the inflows and outflows of the processes. The Information for Steps section shows the data flowing in or produced by each step of the use case, and these correspond to the data flows that enter or leave each process on the data flow diagram. DFD from Use Cases processes, data flows, data stores, and external entities. elements of a DFD grammatical errors made by the analyst when creating the DFD. (easier to find) syntax errors misunderstandings by the analyst in collecting, analyzing, and reporting information about the system. semantics errors reflects how the data will physically be stored in databases and files. physical data model ERD (entity relationship diagramming) a graphic drawing technique that shows all the components of a business system. logical data model