Question

Define each of the following documentation techniques: data flow diagram, document flowchart and system flowchart (6 points)

Discuss the guidelines for a better coding system

What are the four symbols used to develop Data Flow Diagram? (4 points) Note: Define each symbol and mention its usage (drawing is not required)

Answer 1

1.)Data Flow Diagram

A Data Flow Diagram (DFD) is a graphical representation of the “flow” of data through an information system, modeling its process aspects.The data-flow diagram is good for displaying the functions of a system but not good for modeling databases or time-dependent behavior.DFDs can also be used for the visualization of data processing (structured design) and show what kind of information will be input to and output from the system, where the data will come from and go to, and where the data will be stored. It does not show information about the timing of processes or information about whether processes will operate in sequence or in parallel.The diagrams can become as complex as the systems they describe. To reduce the complexity the method used is  breaking up a diagram into manageable pieces creating levels. The first level is  “context” diagram that shows the entire system at a glance.

Document Flowchart

Flowchart is a type of diagram that represents an algorithm ,workflow or process , showing the steps as boxes of various kinds, and their order by connecting them with arrows.Flowchart are used in analyzing, designing, documenting or managing process or program in various field.

Document flowchart traces the physical flow of documents through an organization - that is , the flow documents from the departments, groups or individual who first created them to their final destination.

System Flowchart

This flowchart typically depict the electronic flow of data and processing steps in an Information System.While Document flowchart focus on tangible documents, sytem flowchart concentrates on the computerized data flow of Information System

  2.)

1. Keep codes concise
2. Keep codes stable
3. Make codes that are unique
4. Allow codes to be sortable
5. Avoid confusing codes
6. Keep codes uniform
7. Allow for modification of codes
8. Make codes meaningful

1.Codes should be concise. Overly long codes mean more keystrokes and consequently more errors. Long codes also mean that storing the information in a database will require more memory.

2.Stability means that the identification code for a customer should not change each time new data are received.Don’t change the code abbreviations in a mnemonic system. Once you have chosen the code abbreviations, do not try to revise them, because that makes it extremely difficult for data entry personnel to adapt.

3.For codes to work, they must be unique. Make a note of all codes used in the system to ensure that you are not assigning the same code number or name to the same items.

4.If you are going to manipulate the data usefully, the codes must be sortable.Make sure that users can do what you intend them to do with the codes you create. Numeric codes are much easier to sort than alphanumerics; therefore, consider converting to numerics wherever practical.

5.Try to avoid using coding characters that look or sound alike. The characters O (the letter oh) and 0 (the number zero) are easily confused, as are the letter I and the number 1, and the letter Z and the number 2. Therefore, codes such as B1C and 280Z are unsatisfactory.

6.To be effective and efficient for humans, codes need to follow readily perceived forms most of the time.It is important to keep codes uniform among as well as within programs.

7.Adaptability is a key feature of a good code. The analyst must keep in mind that the system will evolve over time, and the coding system should be able to encompass change. The number of customers should grow, customers will change names, and suppliers will modify the way they number their products. The analyst needs to be able to forecast the predictable changes that business users will desire and anticipate a wide range of future needs when designing codes.

8.Unless the analyst wants to hide information intentionally, codes should be meaningful. Effective codes not only contain information, but they also make sense to the people using them. Meaningful codes are easy to understand, work with, and recall.

3.)

The four major DFD Process,Data ,Entity, Data flow

Process - The process is the manipulation or work that transform data, performing computation, making decisions, or directing data flow based on business rules.In other words, a aprocess receives input and generates some output.Process names usually describe the transformation , which can be performed by people or machines.Process can be drawn as circles or a segmented rectangle on a DFD , and include a process name and process number.

Entity - An entity is the source or destination of data.The source in a DFD represent these entities thar are outside the context of the system.Entities either provide data to the system or receive data from it.Entities are often represented as rectangles.

Data store - A data store is where a process stores data between processes for later retrieval by that same process or another one.Files and tables are considered data stores.Data store names are simple but meaningful.Data stores are usually drawn with the right hand side missing and labeled by the name of the data storage area it represents,though different notations do exist.

Data flow - Data flow is the movement of data between the entity, the process and the data stores.Data flow portrays the interface between the component of the DFD.Data flow is represented by an arrow where an arrow is annotated with the data name.

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