Lesson 3.6 Systems Analysis Flashcards
Explain the logical modeling of processes through studying examples of data-flow diagrams.
Data-flow diagrams are hierarchical in nature، and each level of a DFD can be decomposed into smaller، simpler units on a lower-level diagram. You begin with a context diagram، which shows the entire system as a single process. The next step is to generate a level-0 diagram، which shows the most important high-level processes in the system.
Draw data-flow diagrams following specific rules and guidelines that lead to accurate and well-structured process models.
Several rules govern the mechanics of drawing DFDs. These are listed in Tables 6-2 and 6-3 and many are illustrated in Figure 6-7. Most of these rules are about the ways in which data can flow from one place to another within a DFD.
Decompose data-flow diagrams into lowerlevel diagrams.
Starting with a level-0 diagram، decompose each process، as warranted، until it makes no logical sense to go any further.
Balance higher-level and lower-level dataflow diagrams.
When decomposing DFDs from one level to the next، it is important that the diagrams be balanced; that is، inputs and outputs on one level must be conserved on the next level.
Use data-flow diagrams as a tool to support the analysis of information systems.
Data-flow diagrams should be mechanically correct، but they should also accurately reflect the information system being modeled. To that end، you need to check DFDs for completeness and consistency and draw them as if the system being modeled were timeless. You should be willing to revise DFDs several times. Complete sets of DFDs should extend to the primitive level where every component reflects certain irreducible properties; for example، a process represents a single database operation، and every data store represents data about a single entity. Following these guidelines، you can produce DFDs to aid the analysis process by analyzing the differences between existing procedures and desired procedures and between current and new systems.
Use decision tables to represent process logic.
Process modeling helps isolate and define the many processes that make up an information system. Once the processes are identified، though، analysts need to begin thinking about what each process does and how to represent that internal logic. Decision tables are a simple yet powerful technique for representing process logic.
True or False? RAD methods always model processes separately from the prototypes.
.False
A ___ diagram represents major processes، data flows، and data stores of a system at a high detail level.
Level-0
Conserving inputs and outputs to a DFD process during decomposition is known as ___.
Balancing
