On 6/5/11, Admin Askari <vuaskarihelpline110@gmail.com> wrote:
> *Nice working thanks. But can you make one or examples from amazon.com
>
> Question: Assume the working phenomenon of www.amazon.com, while considering
> their shopping cart mechanism in mind; draw the 'Data Flow Diagram' for a
> specific department with respect to a customer?
> Hint: Visit www.amazon.com and consider acceptable assumptions regarding
> online sales mechanism. Use Microsoft Word or Microsoft Visio for drawing
> DFD.
>
> Note: You have to draw the complete diagram with proper labeling
>
> *
> 2011/6/5 `•..•´ šψεd вяотнêяS `•..•´ <syedbrother1983@gmail.com>
>
>> *
>>
>> n the late 1970s data-flow diagrams (DFDs) were introduced and popularized
>> for structured analysis and design (Gane and Sarson 1979). DFDs show the
>> flow of data from external entities into the system, showed how the data
>> moved from one process to another, as well as its logical storage. Figure
>> 1 <http://www.agilemodeling.com/artifacts/dataFlowDiagram.htm#Figure1>
>> presents
>> an example of a DFD using the Gane and Sarson notation. There are only
>> four
>> symbols:
>>
>> 1.
>>
>> Squares representing external entities, which are sources or
>> destinations of data.
>> 2.
>>
>> Rounded rectangles representing processes, which take data as input, do
>> something to it, and output it.
>> 3.
>>
>> Arrows representing the data flows, which can either be electronic data
>> or physical items.
>> 4.
>>
>> Open-ended rectangles representing data stores, including electronic
>> stores such as databases or XML files and physical stores such as or
>> filing
>> cabinets or stacks of paper.
>>
>>
>>
>>
>>
>> Figure 1. Enrolling in the university.
>>
>> To create the diagram I simply worked through a usage scenario, in this
>> case the use case logic described in the Enroll in
>> University<http://www.agilemodeling.com/artifacts/systemUseCase.htm#Figure1>
>> system
>> use case. On actual projects it's far more common just to stand at a
>> whiteboard with one or more project stakeholders and simply sketch as we
>> talk through a problem.
>>
>> In this case I started with the applicant, the external entity in the top
>> left corner, and simply followed the flow of data throughout the system.
>> I
>> introduced the Inspect Forms process to encapsulate the initial validation
>> steps. I assigned this process identifier 1.0, indicating that it's the
>> first process one the top level diagram. A common technique with DFDs is
>> to
>> create detailed diagrams for each process to depict more granular levels
>> of
>> processing. Were I to do this for this process I would number the
>> subprocesses 1.1, 1.2, and so on. Subprocesses of 1.1 would be numbered
>> 1.1.1, 1.1.2, and so on. I wouldn't bother to expand this process to more
>> detailed DFD as it is fairly clear what is happening in it and therefore
>> the
>> new diagram wouldn't add any value. I also indicated who/what does the
>> work
>> in the bottom section of the process bubble, in this case the registrar.
>> This information is optional although very useful in my experience. You
>> can
>> see how the improperly filled out forms are returned to the applicant if
>> required.
>>
>> I then continued to follow the logic of the use case, concentrating on how
>> the data is processed by each step. The second process encapsulates the
>> logic for creating a student record, including the act of checking to see
>> it
>> the person is eligible to enroll as well as if they're already in the
>> database. Notice how each data flow on the diagram has been labeled.
>> Also
>> notice that the names of the data change to reflect how it's been
>> processed.
>>
>> Now that I look closer at the diagram the arrow between the Input Student
>> Information process and the Student DB data store should be two-way
>> because this process searches the database for existing student records.
>> Unfortunately I've erased this diagram from my whiteboard so it isn't easy
>> to address this minor problem. Yes, I could use a drawing program to
>> update
>> the arrowhead but its more important to make the point that agile models
>> don't need to be perfect, they just need to be good enough. AM recommends
>> that you follow the practice Update Models Only When it
>> Hurts<http://www.agilemodeling.com/practices.htm#UpdateOnlyWhenItHurts>
>> and
>> in this case this issue doesn't hurt enough to invest the two or three
>> minutes it would take to fix the diagram.
>>
>> The Collect Fees process is interesting because it interacts with an
>> electronic data store, Financial DB, as well as a physical one, Cash
>> Drawer. DFDs can be used to model processes that are purely physical,
>> purely electronic, or more commonly a mix of both. Electronic data stores
>> can be modeled via data models, particularly if they represent a
>> relational
>> database. Physical data stores are typically self explanatory.
>>
>> There are several common modeling rules that I follow when creating DFDs:
>>
>> 1.
>>
>> All processes must have at least one data flow in and one data flow
>> out.
>> 2.
>>
>> All processes should modify the incoming data, producing new forms of
>> outgoing data.
>> 3.
>>
>> Each data store must be involved with at least one data flow.
>> 4.
>>
>> Each external entity must be involved with at least one data flow.
>> 5.
>>
>> A data flow must be attached to at least one process.
>>
>> Although many traditional methods have a tendency to apply DFDs in
>> dysfunctional ways it is still possible to do so in an agile manner as
>> well. Keep your diagrams small, as I did above. Use simple tools, such
>> as
>> whiteboards, to create them with your stakeholders. Travel light and
>> erase
>> them when you're through with them. Create them if they're going to add
>> value, not simply because your process tells you to do so. The bottom
>> line
>> is that some of the modeling methodologies may have been flawed but the
>> need
>> to represent the data flow within a system is still required.
>>
>>
>>
>> --
>> Thanks & Regards*
>> *
>> *
>> *Syed Brothers*
>> *MBA Multi Semester Fall 2010*
>> *
>> *
>>
>> --
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