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New Post 5/29/2008 2:36 AM
User is offline Adrian M.
739 posts
3rd Level Poster




Re: Context Diagram: Bank ATM Example 

Hi Guys,

Here's some feedback/answers related to your questions and Level 1 diagrams (not necessarily in same order):

  • Yes - requirements elicitation is an ongoing process! There is no such thing as perfect process, model, system, etc.  The more you are familiar with a system and the given business domain the more you will uncover new requirements and areas which should be refined.  Requirements gathering is an iterative process.  This is why prioritization should be a key concept for every business analyst.  The BA should prioritize at every step in the process; for example at the problem statement state consider which are the most pressing business needs, at vision level consider which features are most important, at the requirements level identify the high priority requirements, at the data flow modeling level identify the key processes.  So at every step work first on the most important things first and then move to the next step of the process (you can refine later) or else you'll never go anywhere.
  • Sonavi: related to the item above - in the Level 1 diagram you need to show the key processes (Withdraw Cash, Deposit Money, etc.) your diagram has none of those.  Things like "Display Error Message" are too detailed at this level and not very important at this time.  Same goes for: "Display Options", "Exit Session", "Send for data input and outputs
  • Data flows from Entities must flow into Processes
  • Data flows to Entities must come from Processes
  • Processes and Data Stores must have both inputs and outputs; what goes in must come out!
  • Inputs to Data Stores only come from Processes
  • Outputs from Data Stores only go to Processes
  • A few more corollaries:
    • There can be no Data Flows between Entities
    • There can be no Data Flows between Data Stores
    • There can be no Data Flows between an Entity and a Data Store
  • - Adrian


    Adrian Marchis
    Business Analyst Community Blog - Post your thoughts!
     
    New Post 5/29/2008 9:17 AM
    User is offline Tony Markos
    493 posts
    5th Level Poster


    Re: Context Diagram: Bank ATM Example 

    Adrian:

    Data Flow Diagrams or Use Cases?

    It has always been my experience that , especially for larger scale efforts, proceeding in a pure top-down fashion (i.e., STARTING with a Context diagram that is anywhere near adequate and then proceeding to lower level diagrams) is not possible.  If an analyst is on a larger scale project where someone, anyone, has, at the start fo the project, an adequate top-down understanding of the essential functionality within the scope of the system, I would say that analyst is in a very rare situation.  Recognizing this unfortunate but typical reality is key, as  it helps explain why good Context diagrams, especially for larger scale efforts, are so rare in the business world.

    It has always been my experience that  the analyst(s)  need to proceed from somewhere in the middle and then go up levels of abstraction.    In other words,  we must first create some lower level data flow diagrams and then summarize them upwards into a Context diagram..  I know, if we could start from a context diagram, analysis would be alot easier.    

    At what point can we switch to use cases?    That point is debatable.  However, for larger scale projects, the required need for data flow diagrams often extends well beyond the Context diagram.

    Tony

     

     

     
    New Post 5/29/2008 3:15 PM
    User is offline Adrian M.
    739 posts
    3rd Level Poster




    Re: Context Diagram: Bank ATM Example 

    Hi Tony,

    I would argue that it is up to the Business Analyst to ensure that they have all they need in order to start with a top-down approach.  Every project should have some sort of charter and problem statement or list of needed features.  I realize that the business analysis process is an iterative one and that not all info gets discovered upfront.  As new info is discovered the models should be updated.

    - Adrian


    Adrian Marchis
    Business Analyst Community Blog - Post your thoughts!
     
    New Post 6/1/2008 10:55 PM
    User is offline Jay
    10 posts
    10th Level Poster


    Re: Context Diagram: Bank ATM Example 

    Hello Adrian and team members

    Thanks for the reply and the feedback.  I have gone ahead and modified the diagrams . I have tried to keep in mind the data flow rules. I have given both the level 1 diagram and the level 2 diagrams. Adrain, would be great if you can tell me whether I am going in the right direction and where I am going wrong. Once this is done, I would like to go ahead and create use case diagrams .

    Would like other team members to participate and give their views and opinions and guide us where we are going wrong.

    Thanks :- Jay

     

     
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    New Post 9/17/2008 4:34 PM
    User is offline OliverG
    8 posts
    10th Level Poster


    Re: Context Diagram: Bank ATM Example 

    Im really struggling with these Dataflow Diagrams.

    Iva attached my level 0 and 1. Level 1 is incomplete as I got so muddled!

    Ive kind of got muddled with what i do and dont need.

    How in depth do you go, that kind of thing?

    Ive moved onto Use cases till Someone can tell me to Bin my WFD!!!!!

    Ok scrap that work firewall wont allow me to upload docs? Can I email them to somebody (and thus lkeep them private! LOL ;0) _

     
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