If you want to buy the project management book mail [email protected]  for more details or call any of our book shops MUMBAI-22078296/97/022-22070989, KOLKATA-22826518/19 HYDERABAD-24756967,24756400,BANGALORE-25587923, 25584641,AHMEDABAD-26421611,BHATINA(PUNJAB)-2237387,CHENNAI-28410796,28550491,DELHI/NEWDELHI-23254990/91,23325760,26415092,24691288.If you want to write to the author directly email at [email protected]
 

Home

(B) How do we estimate using Use Case Points?

Steps for UCP (Use Case Points) Estimation

• Determine the UAW (Unadjusted Actor weight): The first step is to classify all the actors in to the following classification. Table ‘Actor Classification’ will give you a clear idea of how to classify the actors. Second column is the litmus test for making a decision of which type of actor falls in which category. The last column provides the factor of complexity.

Table: - Actor classification

• Determine number of UUCW (Unadjusted Use case Weight): The second step is to count Use Cases and assign weights depending on number of scenarios and number of transactions.

Table: - Use case value factor

• Determine Total UUCP (Unadjusted Use Case Point): Total UUCP = Total UAW + Total UUCW.
• Computing technical and environmental factor: Final step is to take into account the technical complexity. All technical factors will be assigned a value from 0 to 5 depending on complexity.

Table: - Technical Factor

• Equation for Tfactor = sum(T1....T13)
• TCF (Technical Complexity Factor): TCF = 0.6 + (0.01 * Tfactor).
• EF (Environmental Factor): There are other factors like trained staff, motivation of programmers etc. which have quiet a decent impact on the cost estimate.

Table: - Environmental factor

• Efactor = SUM(e1...e8).
• Calculating Environmental Factor = EF = 1.4 + (-0.03 * Efactor).
• AUCP (Adjusted Use Case Points). Finally, calculating the Adjusted Use case points: AUCP = UUCP * TCF * EF
• Multiplying by Man/Hours Factor: AUCP * Person/Hours/AUCP.

Karner[13] proposed a factor of 20 staff hours per Use Case point for a project estimate. While Sharks states that field experience has shown that effort can range from 15 to 30 hours per Use Case point.Schneider and Winters proposed number of staff hours per Use Case point depends on the environmental factors. The number of factors in E1 through E6 that are below 3 are counted and added to the number of factors in E7 through E8 that are above 3. If the total is 2 or less, the general idea is to use twenty staff hours per UCP; if the total is 3 or 4, use twenty-eight staff hours per UCP. If the number exceeds 5, it is usually recommended that changes should be made to the project so the number can be adjusted, because in this case, the risk is unacceptably high. Another possibility is to increase the number of staff hours to thirty-six per

Sample project scope (Sample Data Entry Project):

Let's start with a sample fiction project. Here's the scope of the project. TNC company till now was using manual way of maintaining its customer database and there credit card information. Data entry operator manually validates credit card information from external payment gateway. They maintain customer code, customer name, customer address, customer phone and validated customer credit card information in Customer registry. Customer code is unique for a customer. So, TNC manually checks for the validations and enters in the customer registry. TNC wants the data entry project to be automated. TNC is looking for the following automation:

• Customer code assigned should be checked for uniqueness automatically.
• Customer code should not exceed 8 length.
• Credit card validation should be automatic for the current system. TNC has already given the API documentation of how to interact with the third party payment system.
• Credit card length should not exceed more than 10 length.
• Data entry operator should be able to add/update/delete customer information.
• The database will be in the TNC head office and only data entry operators will be allowed to use the data entry software.
• Software should work on Windows platform. At this moment, TNC has Windows 2000 client installed in all computers.

Writing Use Case for Sample Data Entry Project:

I have used Alistair Cockburn's template for the "Use Case point" example. Use Case template varies from person to person, project to project, and organization to organization. I found Alistair's template to be complete, so just took it. But there's no hard and fast rule that you have to follow this template. What will matter is what steps you write in the Use Case.

Use Case Transactions: It’s an atomic set of activities that are either performed entirely or not all. What is a Use Case transaction and what’s not: just see if the transaction is adding any business value or else do not include it as a transaction. Example: the user switches on the computer, user clicks on add button or any GUI, are not valid business transaction steps. But the customer code validated for credit card information is a valid business transaction. Use Case points are heavily affected by the way the Actors and their transactions are identified. So a Use Case Document should be written by predefined guidelines, uniformly in a project. Just take a meeting with the whole project team before starting writing Use Cases. The depth of the Use Case Document will affect estimation by 40%.

Applying Use Case Points:

Let's start applying Use Case Points to the above given document.

• Determining Unadjusted Use Actor Weights (UAW): In this project, we have identified only one actor “Data Entry Operator”. The upper Actor (data entry operator) is complex as data entry operator will be interacting through GUI. So UAW=3 as per Table:2.0.
• Determine number of UUCW (Unadjusted Use case Weight): There are 12 transactions [Adding also the alternative flows] in Table 6.0 Use Case. So the above Use Case is complex according to Table ‘Use case value factor’. So referring Table ‘Use case value factor’, UUCW=15.
• Now calculating the total UUCP = 15 + 3 = 18.
• Determining the technical factor

• Depending on the table, calculating the Technical Factor: TCF = 0.6 + (0.01 * Tfactor) = 0.6 + (0.01 * 19) = 0.79
• Calculating environmental factor

According to [Kirsten Ribu Master of Science Thesis], Environmental factor plays a very important role in the estimation. A slight variation will increase the Use Case point by a very, very drastic amount. Even small adjustments of an environmental factor, for instance by half a point, can make a great difference to the estimate. Difference of 3 to 2.5 increased the estimate by 4580 hours, from 10831 to 15411 hours, or 42.3 percent. This means that if the values for the environmental factors are not set correctly, there may be disastrous .

• Using formulae for calculating EF = 1.4 + (-0.03 * Efactor) = 1.4 + (-0.03 * 23.5) = 0.695.
• Calculating AUCP = UUCP * TCF * EF = 18 X 0.79 X 0.695 = 9.88 approx = 10 Use Case Points. I have done the approximation as its only creates 3 to 4 hours of difference.
• Calculating according to Karner, i.e., 20 staff hours per Use Case points = 10 X 20 = 200 hours for the total project. If programmer works for 8 hours for a day, then 340/8 = 25 days.
• Calculating according to Schneider and Winters, from e1 to e6 there are only 3 properties that are below 3. And from e7 to e8, there are none whose value is above 3. So the total is 3. We use 28 staff hours. 10 X 28 = 280 hours.

If programmer works for 8 hours, then 35 days. If this step is not understood, look at the steps defined in theory of Use Case points. If we apply sixth sense, we will find Karner approach is coming to round about figure. It really depends what you want to follow: Karner or Schneider approach. Best is that after two or three projects, whatever is coming accurate from history, take that approach. Best approach is to use Excel and incorporate formulas properly.

If you want to buy the project management book mail [email protected]  for more details or call any of our book shops MUMBAI-22078296/97/022-22070989, KOLKATA-22826518/19 HYDERABAD-24756967,24756400,BANGALORE-25587923, 25584641,AHMEDABAD-26421611,BHATINA(PUNJAB)-2237387,CHENNAI-28410796,28550491,DELHI/NEWDELHI-23254990/91,23325760,26415092,24691288.If you want to write to the author directly email at [email protected]
 

Home