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I am studying function point analysis from Alvin Alexander's website. http://alvinalexander.com/FunctionPoints/ In his example, he is calculating DETs from GUI screen but I cannot understand how he is counting. For example according to him at http://alvinalexander.com/FunctionPoints/node26.shtml (end of page) DET of Create Project is five while there are only three input fields. Same is with other Screens. Can anyone help me? I'm stuck here.

Zohaib Aslam
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2 Answers2

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A DET (Data Element Type) isn't just an input field: it's any piece of information recognizable by the user that crosses the application boundary. Usually, every input field on the screen is indeed a DET, but not always. I'm not going to get into that now, though, since in this particular case all the input fields are indeed DETs. Let's just talk about those 2 DETs that seem unaccounted for.

You should count 3 DETs for the 3 input fields (Project Name, Project Type and Project Description), and also 1 DET for the act of clicking on the Save button. Note that even if there were multiple ways to save the project (clicking on the Save button, pressing Enter etc) you would still count only 1 DET.

As for the fifth DET, I'm assuming the author is counting 1 DET for any messages the application is capable of showing in the process of creating a new project (confirmation message, any error messages, warnings etc). Again, you should only count 1 DET no matter how many possible messages there are. And I said I'm assuming because, while it is correct to count 1 DET for the capability of showing messages (it is, after all, information recognizable by the user that crosses the application boundary), he should have explicitly mentioned at least one message, especially since it's a teaching example.

Raquel Peres da Silva
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DET basically count of controls/fields, error message & button/href on UI screen for transaction functions.

 - 1 DET for 1 controls/fields. 
 - 1 DET for all error messages.
 - 1 DET for all buttons/hrefs.

eg, 1 Text field = 1 DET
    1 Label      = 1 DET
    1 Radio button group = 1 DET
    2 Button (Submit & Cancel) = 1 DET

    Total 4 DET.
Nitesh Kumar
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  • Are you sure about considering `cancel` button as a `DET`? I have seen in many books having instructions about not considering `cancel` as a `DET`, since it doesn't make any `transaction`. – Ahashan Alam Sojib Aug 16 '17 at 11:53