Summary

Traditional tools have limitations. An English narrative description is often vague and difficult for the user to grasp. System flowcharts focus more on physical than on logical implementation of the candidate system. Because of these drawbacks, structured tools were introduced for analysis. They include data flow diagrams, a data dictionary, structured English, decision trees, and decision table.
2. The traditional approach to analysis focuses on cost/benefit and feasibility analyses, project management, hardware and software selection, and personnel considerations. In contrast structured analysis considers new goals and structured tool for analysis. Specifically, it uses graphics wherever possible, differentiate between logical and physical systems, and builds a logical system to accentuate s stem characteristics and interrelationships before implementation.
3. The system development life cycle with structured anal_ sis covers six steps:
a. Study affected user areas, resulting in a physical DFD.
b. Remove the physical checkpoints and replace them with the logical equivalent, resulting in the logical DFD
c. Model new logical system.
d. Establish man/machine interface.
e. Quantify costs and benefits.
4. The DFD clarifies system requirements and identifies major transformations that will become programs in system design. It is the starting point in system design that decomposes the requirements specifications down to the lowest level of detail.
5. In constructing DFDs, the analyst should name and number processes for easy reference. The direction of flow is from top to bottom and from left to right. When a process is exploded into lower-level details, they are numbered. The names of data stores, sources, and destinations are written in capital letters.
6. A data dictionary is a structured repository of data about data. It offers the primary advantages of documentation and improving analyst/user communication by establishing consistent definitions of various elements, terms, and procedures. The three classes to be defined are data elements, data structures, and data flows and data stores:
a. Data element is the smallest unit of data that provides for no further decomposition.
b. Data structure is a group of data elements handled as a unit.
c. Data flows and data stores are data structures in motion and data structures at rest, respectively.
7. In constructing a data dictionary, the analyst considers several points:
a. Each data flow in the DFD has one data dictionary entry.
b. Definitions must be readily accessible by name
c. There should be no redundancy in the data definition. Data definition.
d. The procedure for writing definitions should be precise
8. A decision tree sketches the logical structure based on some criteria. It is easy to construct, read, and update. It shows only the skeletal aspects of the picture however, and does not lend itself to calculations. The alternative is structured English.
9. Structured English uses logical constructs and imperative sentences designed to carry out instructions for action. Decisions are made through IF, THEN, ELSE, and SO statements. This tool is highly correlated with the decision tree.
10. A decision table is a table of contingencies for defining a problem and the actions to be taken. It is a single representation of the relationships between conditions and actions. The parts of the table are the stub and entry. The stub is divided into condition and action stubs; the entry is also divided into a condition and an action entry. The rules to follow in constructing decision tables are:
a. A decision should be given a name.
b. The logic of the table is independent of the sequence in which condition rules are written, but the action takes place in the order in which the events occur.
c. Standardized language must be used consistently.
d. Duplication of terms should be eliminated.
11. In comparing the tools covered in the chapter, we find that:
a. The primary strength of the DFD is its ability to represent data flows, but it only weakly shows input and output details.
b. The data dictionary simplifies the structure for meeting the data requirements of the system but does not provide functional details.
c. Structured English is best used when the problem requires using sequences of actions with decisions.
d. Decision trees are used for logic verifications and in problems involving few complex decisions.
e. Decision trees and decision tables are best suited for dealing with complex branching routines.