As an introduction to the assignment ten, base on the assignment eight and nine we are task to make an UML Unified Modeling Diagram-different diagrams that can illustrate a process or system, in our case we are task to illustrate the pre-enrollment of University of Southeastern Philippines. In assignment eight we are task to develop an activity diagram and a fully developed description for a use case. Activity Diagrams are usually used to a business process model, for modeling the logic captured by a single use case of a business or a system, it is also for modeling the detailed logic of a business rule or the rules of the system how it works. Creating activity diagrams are very useful in describing the flow control of the target system. It is also helpful in determining the use cases and the business processes of a company or a system that a company may use. With the assignment nine we are task to create at least 3 different types of Data flow diagram of USEP's pre-enrollment system. First we defined what data flow diagram is all about. Data flow diagram is a graphical representation of data on how the process goes in the system or business. According to Scott W. Ambler data flow diagram shows the flow of the data from external entities into the system, how the data moved from one process to another as well as its logical storage. Data flow diagram can also be used for the visualization of data processing. A Data flow diagram provides no information about the timing of processes, or about whether processes will operate in sequence or in parallel. It is therefore quite different from a flowchart, which shows the flow of control through an algorithm, allowing a reader to determine what operations will be performed, in what order, and under what circumstances, but not what kinds of data will be input to and output from the system, nor where the data will come from and go to, nor where the data will be stored. Also according to Hoffer, George and Valacich there are two defined data flow diagrams, includes context diagram and level-O diagrams. To differentiate, context diagram is a data flow diagram (DFD) of the scope of an organizational system that shows the system boundaries external entities that interact with the system and the major information flows between the entities and the system. On the other hand, level-O diagram is a data flow diagram (DFD) that simply represents a system’s major processes, data flows and data stores at a high level detail.
The data flow diagram has a purpose and it provide the meaning between users and systems developers. And it diagrams are first graphical, eliminating thousands of words; second is logical representations, modeling WHAT a system does, rather than physical models showing HOW it does it; third is hierarchical, showing systems at any level of detail; and allow the user to understand review the process.
There are characteristics examined in evaluating the data flow diagram. First is Remember, also referred to as recognition or recall. Be able to remember or recognize terminologies, definitions, facts, ideas, materials, patterns, sequences, methodologies and principles. Second is to Understand. Will be able to read and understand descriptions, communications, reports, tables, diagrams, directions and regulations. Third is to Apply. Be able to apply the ideas, procedures, methods, formulas, principles, theories and to the related situation that can be apply on the diagram. Fourth is Analyze. To be able to break down information into its constituent parts and recognize the parts’ relationship to one another and how they are organized; understand the data’s from a complex process. The fifth one is to Evaluate. To be able to make judgments regarding the value of proposed ideas, solutions, methodologies, and many more by using the proper standards to estimate accuracy, effectiveness, economic benefits, and many more. The last one is to Create. Be able to identify which data or information from a complex set is appropriate to examine further or from which its supported conclusions can be drawn.
Data flow diagram has the following symbols: Process flow diagrams. It has the following entities, process number, where the activity is happening and its process name. Data flow datagram. It symbolizes the transformation of data, there must be data flowing into/out of the process, process can have several inputs to it or output to it and process with no out becomes a null process. Data store Symbol. Consist of the following entities, data store number and name of data store. The function of data store is to designate the storage of data in a DFD diagram. Rules of Data store-First rule is that the data flow diagram data store do not by level but they may reappear incase needed and secondly that the symbol and the numbering remain the same. Data flow symbol. Data flow symbol may appear in different shape and they signify the movement of data. They do not signify the movement of people, goods. Doubles an arrow signifies that activities occur at the same time which is wrong and Data flow in is never equal to data flow out. Extended entity symbol. Extended entity is sources and destination of data. This means that source is the origin and destination is the sink of data.
Dos and Don’ts of external entity
• External entity never communicate with each other, this signify that there is no need for the process
• External entity should not communicate directly with data store because external entities can be identifier with the record of files and databases
How to develop Logical data flow diagram
Below are the guidelines in developing data flow diagrams
1. Develop a physical DFD
2. Explore the process for more details
3. Maintain consistency between the process
4. Following meaningful leveling convention
5. Ensure that DFD diagrams clarifies what is happening in the system
6. Remember DFD audience
7. Add control on the lower level DFD only
8. Assign meaningful level
9. Evaluate DFD for correctness
Step in drawing DFD diagrams
1. Make a list of all business activities and use it to determine the various external entities, data flows, process and data store
2. Create a context diagram which shows external entity and data flows to and from the system
3. Do not show any detailed process or data store
4. Draw diagram zero or the next level to show process but keep them general. Show data stores and the level
5. Create a child diagram for each of the process in diagram zero
6. Check for errors and make sure the levels you assign to each process and data flow are meaningful
7. Develop a physical DFD diagram from the logical DFD and distinguish between the manual and automated protocol, describe actual files and report by name and controls to indicate when the process are complete or errors occurs
8. Portion the physical DFD by separating or grouping parts of the diagram in order to facilitate programming and implementation
Advantages of data flow diagrams
• It gives further understanding of the interestedness of the system and sub-systems
• It is useful from communicating current system knowledge to the user
• Used as part of the system documentation files
• Dataflow diagram helps to substantiate the logic underlining the dataflow of the organization
• It gives the summary of the system
• DFD is very easy to follow errors and it is also useful for quick reference to the development team for locating and controlling errors
Disadvantages of data flow diagram
• DFD is likely to take many alteration before agreement with the user
• Physical consideration are usually left out
• It is difficult to understand because it ambiguous to the user who have little or no knowledge.
Data Flow Diagram Principles
* The general principle in Data Flow Diagramming is that a system can be decomposed into subsystems, and subsystems can be decomposed into lower level subsystems, and so on.
* Each subsystem represents a process or activity in which data is processed. At the lowest level, processes can no longer be decomposed.
* Each 'process' (and from now on, by 'process' we mean subsystem and activity) in a DFD has the characteristics of a system.
* Just as a system must have input and output (if it is not dead), so a process must have input and output.
* Data enters the system from the environment; data flows between processes within the system; and data is produced as output from the system
1. A system can be decomposed into subsystems, and
subsystems can be further decomposed into lower level
subsystems.
2. Each subsystem represents a process or activity in which
data is processed.
3. At the lowest level, processes can no longer be decomposed.
4. Each 'process' has the characteristics of a system. A process
must have input and output.
5. Data enters the system from the environment, data flows
between processes within the system and data is produced
as output from the system.
General Data Flow Rules
1. Entities are either 'sources of' or 'sinks' for data input and outputs - i.e. they are the originators or terminators for data flows.
2. Data flows from Entities must flow into Processes
3. Data flows to Entities must come from Processes
4. Processes and Data Stores must have both inputs and outputs (What goes in must come out!)
5. Inputs to Data Stores only come from Processes.
6. Outputs from Data Stores only go to Processes.
Now, back to the main question, what characteristics does an analyst (you) examine when evaluating DFD quality? To be honest, I really had a hard time thinking of how to create good and perfect data flow diagrams. But with the guidelines above information that is mentioned I think I can evaluate A data flow diagram.
References:
http://hubpages.com/hub/What-is-a-data-flow-diagram
http://www.agilemodeling.com/artifacts/dataFlowDiagram.htm
http://www.asq.org/certification/quality-process-analyst/bok.html
http://www.cmp.jobs/qa-analyst-1153.php
http://spot.colorado.edu/~kozar/DFDtechnique.html
No comments:
Post a Comment