Terms in this set (35)
data flow diagram
Systems analysts use many graphical techniques to describe an information system. One popular method is to draw a set of data flow diagrams. A ________ _________ _______ (_______) uses various symbols to show how the system transforms input data into useful information.
processes,data flows,data stores,entities
DFDs use four basic symbols that represent ___________, _______ _______, ________ ______, and __________.
Gane and Sarson, Yourdon
DFD examples in this textbook use the _______ and _________symbol set. Another popular symbol set is the __________ symbol set.
A _________ receives input data and produces output that has a different content, form, or both. For instance, the process for calculating pay uses two inputs
Processes contain the _________ _______ , also called business rules , that transform the data and produce the required results.
In DFDs, a process symbol can be referred to as a ________ ________ , because the inputs, outputs, and general functions of the process are known, but the underlying details and logic of the process are hidden.
A _______ _______ is a path for data to move from one part of the information system to another. A data flow in a DFD represents one or more data items.
______________ ____________ . The APPLY INSURANCE PREMIUM process, for instance, produces output, but has no input data flow. Because it has no input, the process is called a spontaneous generation process.
_________ ___________ . The CALCULATE GROSS PAY is called a black hole process, which is a process that has input, but produces no output.
_______ _______ . A _______ ______is a process that has at least one input and one output, but the input obviously is insufficient to generate the output shown. For example, a date of birth input is not sufficient to produce a final grade output in the CALCULATE GRADE process.
A ________ _________ is used in a DFD to represent data that the system stores because one or more processes need to use the data at a later time.
The symbol for an _______ is a rectangle, which may be shaded to make it look three-dimensional. The name of the entity appears inside the symbol.
terminators , source,sink
3.DFD entities also are called _________, because they are data origins or final destinations. Systems analysts call an entity that supplies data to the system a ________ , and an entity that receives data from the system a ________.
context diagram,process 0
The first step in constructing a set of DFDs is to draw a _________ _________. A __________ __________ is a top-level view of an information system that shows the system's boundaries and scope. To draw a context diagram, you start by placing a single process symbol in the center of the page. The symbol represents the entire information system, and you identify it as __________ ____
In the previous step, you learned that a context diagram provides the most general view of an information system and contains a single process symbol, which is like a black box. To show the detail inside the black box, you create DFD ___________ ___. __________ __ (the numeral zero, and not the letter O) zooms in on the system and shows major internal processes, data flows, and data stores. __________ ___ also repeats the entities and data flows that appear in the context diagram. When you expand the context diagram into DFD ________ _____, you must retain all the connections that flow into and out of process 0.
diverging data flow
A __________ _____ _____ is a data flow in which the same data travels to two or more different locations. In that situation, a diverging data flow is the best way to show the flow rather than showing two identical data flows, which could be misleading.
parent diagram,child diagram
Because diagram 0 is an exploded version of process 0, it shows considerably more detail than the context diagram. You also can refer to diagram 0 as a partitioned or decomposed view of process 0. When you explode a DFD, the higher-level diagram is called the ＿＿＿＿＿＿＿＿＿＿＿＿＿ , and the lower-level diagram is referred to as the ＿＿＿＿＿ _______ . The grading system is simple enough that you do not need any additional DFDs to model the system. At that point, the four processes, the one data store, and the 10 data flows can be documented in the data dictionary.
When you create a set of DFDs for a system, you break the processing logic down into smaller units, called _________ _________, that programmers will use to develop code. A _________ ___________ is a process that consists of a single function that is not exploded further.
2.To create lower-level diagrams, you must use ________ and _________ techniques. _________ is the process of drawing a series of increasingly detailed diagrams, until all functional primitives are identified. ________ maintains consistency among a set of DFDs by ensuring that input and output data flows align properly.
More complex systems have more processes, and analysts must work through many levels to identify the functional primitives. Leveling also is called __________ , partitioning , or ___________ .
data dictionary,data repository
A ______ ____________, or _______ ___________ , is a central storehouse of information about the system's data. An analyst uses the data dictionary to collect, document, and organize specific facts about the system, including the contents of data flows, data stores, entities, and processes.
data element,records,data structures
4. A _______ ___________ , also called a data item or field , is the smallest piece of data that has meaning within an information system. Examples of _____ __________ are student grade, salary, Social Security number, account balance, and company name. Data elements are combined into ______ , also called ______ _____________.
2. Specification of the data element's ________ , which is the set of values permitted for the data element; these values either can be specifically listed or referenced in a table, or can be selected from a specified range of values. You also would indicate if a value for the data element is optional. Some data elements have additional ________ _________
Any name(s) other than the standard data element name; this alternate name is called an ＿＿＿＿＿＿ . For example, if you have a data element named CURRENT BALANCE, various users might refer to it by alternate names such as OUTSTANDING BALANCE, CUSTOMER BALANCE, RECEIVABLE BALANCE, or AMOUNT OWED.
Each data flow represents a group of related data elements called a ＿＿＿＿＿ or data structure. In most data dictionaries, ＿＿＿＿＿ are defined separately from the data flows and data stores. When records are defined, more than one data flow or data store can use the same record, if necessary.
Modular design, control structures 基準寸法[モジュール]の[による].
＿＿＿＿＿＿ ＿＿＿＿＿＿ is based on combinations of three logical structures , sometimes called _________ __________ , which serve as building blocks for the process. Each logical structure must have a single entry and exit point
___________. The completion of steps in sequential order, one after another, as shown in Figure 5-30. One or more of the steps might represent a subprocess that contains additional logical structures.
_____________.The completion of one of two or more process steps based on the results of a test or condition. In the example shown in Figure 5-31, the system tests the input, and if the hours are greater than 40, it performs the CALCULATE OVERTIME PAY process.
__________The completion of a process step that is repeated until a specific condition changes, as shown in Figure 5-32. An example of iteration is a process that continues to print paychecks until it reaches the end of the payroll file. Iteration also is called looping .
___________ __________ is a subset of standard English that describes logical processes clearly and accurately. When you use structured English, you must conform to the following rules:
Use only the three building blocks of sequence, selection, and iteration.
Use indentation for readability.
Use a limited vocabulary, including standard terms used in the data dictionary and specific words that describe the processing rules.
A _______ ________ is a logical structure that shows every combination of conditions and outcomes. Analysts often use decision tables to describe a process and ensure that they have considered all possible situations. You can create decision tables using Microsoft PowerPoint, Word, or Excel.
A ________ ________ is a graphical representation of the conditions, actions, and rules found in a decision table. Decision trees show the logic structure in a horizontal form that resembles a tree with the roots at the left and the branches to the right.
logical model ,physical model
2.While structured analysis tools are used to develop a _________ ________for a new information system, such tools also can be used to develop physical models of an information system. A _________ _________ shows how the system's requirements are implemented. During the systems design phase, you create a _________ ________ of the new information system that follows from the logical model and involves operational tasks and techniques.
Many analysts follow a ______-________ _______, which means that they develop a physical model of the current system, a logical model of the current system, a logical model of the new system, and a physical model of the new system. The major benefit of the four-model approach is that it gives you a clear picture of current system functions before you make any modifications or improvements. That is important because mistakes made early in systems development will affect later SDLC phases and can result in unhappy users and additional costs.
Logical Model VS Physical Model
A logical model shows what the system must do, regardless of how it will be implemented physically. Later, in the systems design phase, you build a physical model that describes how the system will be constructed.