With reference to assignments 8 and 9, what characteristics does an analyst(you) examine when evaluating DFD quality?
Before enumerating those characteristics of Data Flow Diagrams that the system analyst should examine, let’s discuss first what a diagram is and why it is used when designing systems.
So, Diagrams are tools that aid the system developer on designing and developing systems. Diagrams, in general, are created to better understand the processes that the system performs and what are the sub-sets or sub-systems that are included on that system. A system is too broad if it is to be examined in general, so diagrams are created in order for the developer to have views on the processes and actions the system undertakes. Naturally, we cannot see the processes that the system undergoes with our eyes. Diagrams create different views of the system processes for the developers and with this, developers will be able to evaluate and redesign (if it is needed) those processes that may not be efficient or suspicious. When it comes in designing systems, it could be a great help for the developers if system process is defined in terms of diagrams. With this, developers can track data inputs and outputs from one process to another.
As to what I mentioned awhile ago, a system can be too broad if we are going to look it into the outside. Some processes may be visible but not as detailed or not as specific as on how it process those data that are has been inputted or how it generates output. Diagrams can represent processes with different levels or depth depending on the needs of the designer. If it is just the general processes of the system is represented in the diagram or it could be the sub-processes of that process in the system.
What is Data Flow Diagram? It is a modeling significant modeling technique for analyzing and constructing information processes. Data Flow Diagram shows how the movement of information throughout the processes based on inputs and outputs given by each processes in the system. Data Flow Diagram illustrates technical or business processes with the help of the external data stored, the data flowing from a process to another, and the results. First, the system designer draws a context-level Data Flow Diagram which shows the relationship of the internal and external entities as single step, input and outputs [1]. Data Flow Diagram provides isolation of data which is called data stores that are derived from a process steps being executed within the system processes [2]. Some key characteristics of Data Flow Diagram that are mentioned by Charles(1999) are:
Two-dimensional Summary – Data Flow Diagram summarizes data flow characteristics of of a process on a single page and can provide a useful and concise summary of system-related process attributes. An example of this system-related process that mentioned by Charles(1999) is data-driven processes. This processes are dependent on the data that is being processed. This processes also takes its actions based on what kind of data is passed on it.
Completeness – When creating the Data Flow Diagram of a system, it is easily to look after those components that are needed for the system since it represents your idea of the data that is being inputted and produce by each processes in the system.
Processing, not processes – This term or word may be confusing when it comes in designing Data Flow Diagrams, process. We refer process as the movement of data throughout the system but in Data Flow Diagram, process is the “steps” or operations made in requiring and outsourcing data on the process, processing work.
Patterns – Data Flow Diagram helps the system designer to track which processes requires, stores and generates data or those processes that do not need any. With this, system designer can pin-point critical sections of the system and provide supports or revisions to it.
Another thing that we should know about Data Flow Diagram is those symbols that are used in making one. This symbols represents each entities or processes which is required in the designed system. These symbols and their descriptions are as follows:
Source – it is any data that is identified outside the boundary of the process that Data Flow Diagram is modeling [2]. For example, in UseP's pre-enrollement process, the data source are those requirements like personal information, form 138, certificate of moral conduct and 2x2 pictures that is needed at the UGTO in order to proceed to the process of the pre-enrollment process.
Processing Step – it is the activity that process data. It is presumed that the processing is important enough to play a significant role in the system's process that Data Flow Diagram is modeling [2]. Processing step may or may not be sound as if there is data processing involved but it is still relevant enough to the design system. For example, in UseP's pre-enrollment process, “Get Examination Schedule” process in a Data Flow Diagram in Assignment # 9 describes the processing actions that should be done in order to process the request.
Data Store – it is not the same way as Database. It is a collection of accumulated data that is used by the process. This accumulated data may not in in form of an electronically created file but it could be as papers records. One thing that is why we design Data Flow Diagram is for us to identify entities that is in the data store which serves as the basis of designing Database using Entity Relationship Diagram [2].
Data Flow(s) – it is represented by arrows and labeled with the data that is passed to another process and the arrowhead indicated where data is passed to [2]. Data that was on the data flow are the results of a process in the system which serves as a requirement for the proceeding process of the system.
And now that we know what is Data Flow Diagram is about, let us find out what characteristics does an analyst examine when evaluating Data Flow Diagram quality. First, we should know what are the requirements of the system and does it have representation on the Data Flow Diagram. It was mentioned above by Charles (1999) as one of the characteristics of a Data Flow Diagram is completeness. It is important that all requirements of the system (atleast) was on the Data Flow Diagram because as what is mentioned above, processes is presumed to be important enough when modeling the Data Flow Diagram of the system. So, any missing process or entity may result into inefficiencies in the Data Flow Diagram. Completeness in the diagram makes it more clear when someone will review the processes or when presenting it to those who are concern. At it was said on a quotation, “It's the first impression and will either open the door or close it”. The first thing that will undergo on the test of quality of Data Flow Diagrams is how the diagram looked like. It should give (in general) to those who will look at the diagram what are the processes that occur on the system and those external entities that is needed on the modeled system. These also refers to the symbols used in creating the Data Flow Diagram, correct symbols should be observed and used when defining processes and other entities of the system being modeled. Second, Data Flow Diagram is modeled based on the system requirements so by virtue, Data Flow Diagram should summarizes the processes and actions that the modeled system has. Ala dapat dagdag-bawas unless if it is beneficial to the system being designed. Third, the Data Flow Diagram should enables the analyst to determine critical parts of the system being modeled (processes that requires large amount of data) and be able to observe activities that occurs on every process the modeled system conducts. Data that are passed on the proceeding processes should be stated and as it is expected from the previous process. Fourth, Data Flow Diagram must also identifies those processes that can be analyze further. By creating levels of the processes on the modeled system, the analyst can have a closer look to the underlying processes in a process of the modeled system. And lastly which does not actually refer to the diagram but to those who analyze the Data Flow Diagram. Analyst should keep in mind the goals why the the analysis is conducted, it is to modeled and design that will meet the requirements set by the benefactors and make the modeled system effective and efficient. Analyst should be observant, every details that are presented on the diagram should have taken into account by the analyst and treat it as relevant date for the analysis. Analyst should also have the knowledge and insights on the processes that a system is required to do and all other ideas that makes its processes more efficient and be able to express those ideas by means of plotting it on the Data Flow Diagram.
References:
1. Data Flow Diagram
http://www.edrawsoft.com/Data-Flow-Diagrams.php
2. Data flows: Note on Data-Driven Process Modeling - Data Flow Diagramming by Charles Osborn 1999
http://faculty.babson.edu/dewire/Readings/dfddiag.htm
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