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New Post 5/14/2008 6:42 PM
User is offline Jay
10 posts
10th Level Poster


Re: Context Diagram: Bank ATM Example 

Hello Adrian

 

Thanks a lot for your feedback. I apologize for the mistakes and my limited knowledge. This is my first attempt of a context diagram or anything I will be creating in the near future. Be prepared for the worst but the efforts are sincere. I hope to give it my best and am glad there are other team members participating too.

 

Thanks a lot : Jay

 
New Post 5/14/2008 9:18 PM
User is offline sonavi
37 posts
9th Level Poster


Re: Context Diagram: Bank ATM Example 

Hi Adrian

Thank you for your valuable advise. I have few questions, you mentioned that  the relationships among processes and entities in a Context Diagram show Data Flow and not actions.  Therefore the relationships should not be named as "Verb Noun" but just  "Noun".

1. At the Level 0 diagram do we just show the external entities interacting with the system and not show different process how the systems is interacting with the external entities like ( cash withdraw, deposit, error message, transfer between a/c, print balance, etc)

2. If we show just the external entities interacting with the system then how do you name them for eg ( customer interacting with Cyber ATM bank)

3. What is the next step after the Level 0 diagram?

Thanks

sonavi

 

 

 
New Post 5/14/2008 11:24 PM
User is offline Adrian M.
686 posts
3rd Level Poster




Re: Context Diagram: Bank ATM Example 

Hi Jay & Sonavi,

You are most welcome!

Here are some quick answers to Sonavi's questions:

  1. Yes.  In the Level 0 of the Data Flow Diagram, also called Context Diagram, the only things included are:
    • The process or system being analyzed and described depicted as one process.
    • The external entities which the system/process exchanges data.
    • The data stores with which the system/process exchanges data.
  2. In general, external entities, similar to actors in Use Case diagrams, should be named using the same terms that the business or stakeholders.  Introducing new names for the same things will, in long term, only cause more confusion.  For example:
    • If the customer interacts with the process then just call the entity "Customer" unless you have multiple types of customers which may exchange different type of data with the process/system.
    • If the external entity is another system then use the existing system name. Ex: "Cyberbank Loan Processing System"
    • If the external entity is an organization then user the organization name.  Ex: "ACME Widget Maker"
  3. After Level 0 you decompose the main process/system into key sub processes which becomes the Level 1 diagram.  After that each sub-process in Level 1 is further decomposed (if needed and it makes sense) into further sub-processes which now become part of the Level 2 set of diagrams.  Theoretically, you can have as many levels as you want.  The purpose of the levels is to break down a complex process/system into manageable pieces.  How many levels you are going to have and how many processes you should show at one level is somewhat arbitrary and depends on the complexity of your data flows.  Use common sense.  For example:
    • BAD: having only Level 0 with one process and then in Level 1 having the main process decomposed into 100 sub-processes is not a good thing.
    • BAD: having Level 0 and then Level 1 - 20 where in each Level x diagram you only have 2 sub-processes doesn't sound good either.

I think that you guys should now take another try at creating the Level 0 and maybe Level 1 of the Data Flow Diagram.  You should both do it independently since there isn't just one "right/exact" way of modeling this.

BUT FIRST: However, before you guys move on to that step, you should Google "Data Flow Diagram" and "Context Diagram" and each one of you should post a short tutorial on the subject.  This will force you to learn the subject matter and make it stick.  Focus on: What is a Data Flow Diagram, What is a Context Diagram, What are the main symbols of the DFD and what do they represent, a couple of best practices when creating DFDs.  FYI: There are two popular notations for DFDs: "Gane-Sarson" and "Yourdon-DeMarco" named after the brilliant guys who came up with this stuff.  For some reason, don't ask me why, I have predominantly used the "Gane-Sarson" notation - maybe it has to do with the available notation in my modeling software.

Here are some links to get you started:

Up to the challenge???

;-)  Adrian


Adrian Marchis
Modern Analyst Blog - Featured Business Analyst Blog
Business Analyst Community Blog - Post your thoughts!
 
New Post 5/15/2008 8:25 AM
User is offline sonavi
37 posts
9th Level Poster


Re: Context Diagram: Bank ATM Example 

Wow, that was a great explanation. I am ready for the Challenge!!!. I will post a short tutorial on DFD / Context diagram and start working on the DFD diagram for cyber bank ATM example.

I have another request from all the Sr.Business Analyst.  Adrian is being very helpful in explaining the concept and giving his valuable advise and suggestion and we are very thankful to him that he is  explaining and guiding us. I would request even other Sr.Business Analyst to please help new people like us by giving their advise and suggestions and helping us to learn more.

 

Thanks

-Sonavi

 
New Post 5/15/2008 11:50 AM
User is offline sonavi
37 posts
9th Level Poster


Re: Context Diagram: Bank ATM Example 
Modified By sonavi  on 5/15/2008 2:46:54 PM)

Hello Everyone,

 

I found this wonderful PPT on DFD online. Hope this can help others also i found it useful for me.

I have attached  the Context Level Diagram for Bank ATM example. I had few questions while working on context level diagram. I was not able to attach two files at the same time so i am attaching the DFD PPT in my next message.

1. I read online in a document that we dont include data store in the context level diagram, but we use it in the next level diagrams. Is this correct?

2. I didnt know the exact procedure as to how the cheques and non-cash instruments will be collected from the ATM. Is there a seperate process for that or do the cyber bank employees go and collect them. I have drawn a two-way process in the context level diagram is that how we are supossed to handle.

3. I had hard time in naming the realtionships becasue as suggested by Adrian i didnt use the verbs. Please correct me if i need to change the names of the realationships.

 

 I would appreciate if all the Sr. Business Analysts can point out my mistakes and give their valuable advise.

Thanks

sonavi

 
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