So#ware Effort Es-ma-on With Use Case Points

So#ware Effort Es-ma-on With Use Case Points

1 Ho Tuong Vinh

How Do I Start The So#ware Development ?

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Use Case Defini-on A Use Case consists of: •  Actor(s) : Actors can be persons, but also interfaces with other systems.

•  Goal: An Actor should have a goal that (s)he tries to accomplish

•  Main scenario: This scenario describes the steps to take to accomplish the earlier described goal.

•  Alterna-ve scenarios: Due to business rules such as constric-ons, or due to judgment by the actor, Alternate scenarios may be described.

•  Pre-‐ condi-on: Condi-ons that must be fulfilled before at the Start of the Scenario

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Use Case example

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A sample User-‐Goal Use Case

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This use case is from a job pos-ng and search site. It describes the situa-on in which a third-‐party recruiter has already posted a job opening on the site and now needs to submit payment for placing that ad.

A sample User-‐Goal Use Case

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Main Concepts of Use Case Points

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UCP = Use Case Points UUCW = Unadjusted Use Case Weight UAW = Unadjusted Actor Weight TCF = Technical Complexity Factor ECF = Environment Complexity Factor PF = Produc-vity Factor

Unadjusted Actor Weight

Actors are classified as simple, average and complex.

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Unadjusted Use Case Weight Use Cases are classified as simple, average and complex.

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–  a use case transac-on as a "round trip" from the user to the system back to the user; a transac-on is finished when the system awaits a new input s-mulus.

–  In other words, in one transac-on the actor performs some ac-on which is input for the system. Then the system reacts; i.e., it processes the input and returns the result to the Actor.

UCP calcula-on

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TCF = 0.6 + (0.01 * TFACTOR)

EF = 1.4 + (-‐0.03 * EFACTOR)

Effort = UCP * Produc>vity Factor

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UCP calcula-on -‐ 1

Actor Type Description Multiplier # of Actors Totals Reasons

Simple System Interface 1

Average Interactive I/F 2

Complex Graphical I/F 3

Total Unadjusted Actor Weights (UAW)

Step 1. Tabulate Actors: Obtain UAW, Unadjusted Actor Weights Step 2. Tabulate Use Cases: Obtain UUCW, Unadjusted Use Case Weights Step 3: Total Unadjusted UCP, UUCP = UAW + UUCW

Use Case Type Description Multiplier

(Given) # of Use Cases Reasons Total

Simple 1-3 Transactions 5

Average 4-7 Transactions 10

Complex > 8 Transcations 15

Total Unadjusted Use Case Weights (UUCW)

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UCP calcula-on -‐ 2 Step 4: Iden>fy & grade Complexity Factors: Obtain TCF

TCF = 0.6 + (0.01 * TFACTOR)

Factors Description Weight (Given)

Assigned Values (0-5) Total

T1 Must have a distributed solution 2

T2 Must respond to specific performance objectives 1

T3 Must meet end-user efficiency desires 1

T4 Complex Internal Processing 1

T5 Code must be reusable 1

T6 Must be easy to install 0.5

T7 Must be Easy to Use 0.5

T8 Must be Portable 2

T9 Must be Easy to Change 1

T10 Must allow concurrent operations 1

T11 Include Special Security Features 1

T12 Must provide direct access for 3rd parties 1

T13 Requires special user training facilities 1

TOTAL TFACTOR

0-‐ irrelevant 3-‐ average 5-‐ essen-al

TCF < 1: reduce UCP TCF > 1: increase UCP

Project’s complexity

TCF reduce in maximum 40%, increase 30%

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UCP calcula-on -‐ 3 Step 5: Iden>fy & grade Environment Factors: Obtain EF EF = 1.4 + (-‐0.03 * EFACTOR)

UCP EnvF Description Weight

(Given) Assigned

Values (0-5) Total

E1 Familiarity with the VSII Process 1.5

E2 Application Experience 0.5

E3 OO Experience 1

E4 Lead Analyst Capability 0.5

E5 Motivation 1

E6 Stable Requirements 2

E7 Part Time Workers -1

E8 Difficult Programming Language -1

TOTAL EFACTOR

E1-‐E4 0-‐ no experience 3-‐ average 5-‐ expert

EF reduce in maximum 57.5%, increase 40%

Team’s experience

E5 0-‐ no mo-va-on 3-‐ average 5-‐ high mo-va-on

E6 0-‐ unchanging 3-‐ average 5-‐ extremely unstable

E7 0-‐ no part-‐-me 3-‐ average 5-‐ all part-‐-me

E8 0-‐ easy 3-‐ average 5-‐ difficult

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UCP calcula-on -‐ 4 Step 6: UCP = UUCP * TCF * EF Step 7: Effort in Person-‐Hours = UCP * Produc>vity Factor

Determine Produc>vity Factor From industrial reports: PF = (10 ÷ 30) person-‐hours per UCP Or From your past projects (Update PF: A#er the project completes, compute new PF ( new PF = Actual Effort / UCP)

Adjus>ng Man-‐hours for Risk Risk coefficients to adjust an es-mate when a project includes specific risk that cannot be compensated for within the model itself

Adjusted Effort = (1 + XX [%]) x Measured Effort

Prac-cal exercise

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The requirement for construc>on of a Web site The website should order photos into galleries. The visitor

can review a thumbnail and request to see the full image. The full image will have descrip-on such as camera used, f-‐stop, shuker speed, focal length and ar-s-c comment. My bio and contact informa-on is available as well as email. I should be able to upload photos, thumbnails and descrip-ons easily. The website should cost less than $100 to host.

Your task: give an es-mate of effort for construc-ng the site

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Use-‐Case Structure Makers

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•  Generaliza>on between actors: If two actors have 80 percent in common, put them in generaliza-on rela-onship and count them only once.

•  Included and extending Use Case: are essen-al func-onali-es, and reducing them will reduce steps and hence the es-ma-on.

•  Level of detail in the Use Case descrip>on : The level of detail and transac-on in Use Case impact the Use-‐Case es-ma-on a lot. So if that transac-on step is not adding business value, do not add it as transac-on step. This will also increase the es-ma-on to a good level.

•  Use-‐Case Spligng and Merging: Simple Use-‐Case masters maker a lot. Wri-ng Use-‐Cases, for example “Adding Country Master". User can write three different Use Cases for Add, Update, Delete; or he can write one Use-‐Case and put the Update and Delete in alternate scenarios. If the Update and Delete do not have different business valida-ons, put them in one Use-‐Case. During my coun-ng, I had seen that accuracy increases if for simple master we put them in one Use-‐Case.

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Wri-ng effec-ve use case

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Important terms v  Ac>on step: Single ac-ve-‐verb phrase/sentence v  Actor: Someone playing a role (e.g. teacher, student) v  Scenario: Narra-ve describing how an actor achieves a goal through a series of ac-on steps v  Use Case: Collec-on of scenarios, expressing all possible behaviours as actor tries to achieve goal

Wri-ng effec-ve use case (2)

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Project, System, Service

Use case

Use case

Use case

Use case

Use case

Scenario Ac-on step Ac-on step Ac-on step Ac-on step Ac-on step Ac-on step Use case


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Alan, a maths lecturer, uses a learning object repository to find a simula-on of the behaviour of an equa-on. He logs in using his Athens account, searches using suitable keywords, finds the object and obtains a reference to the object that he uses in the class web site. He demonstrates the simula-on in a lecture by using the class web site.

Write use case that:

–  Describes usage, not requirements –  Defines key stakeholder (primary actor) and his goal –  Lists the ac-on steps in a narra-ve text –  Scenarios are o#en wriken to reflect success


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Goal: Teacher locates a learning object in a repository and uses it in another web site

Primary actor: Teacher Other actors: repository, authen-ca-on system, web site

Main success scenario: 1. Teacher logs into repository with ATHENS authen-ca-on 2. Teacher searches for object by keywords 3. Teacher iden-fies suitable object 4. Teacher obtains reference to object 5. Teacher uses reference in web site

Other scenarios (extensions): 1a. Teacher’s authen-ca-on refused (fail) 1b. Teacher authen-cates using a local LDAP authen-ca-on (s) 3a. Teacher cannot find suitable object (f)

Ac>on Steps

Use Case Defini-on

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•  Use Case Model –  Describes a system’s func-onal requirements –  Consists of all the users (actors) and all the use cases –  Iden-fies reuse via use case inclusions and extensions

•  Use Case –  A use case is a single task, performed by the end user of a system, in

interac-on with the system, that has a useful outcome –  The end user may be a human or another system –  Examples: Iden-fy Subject in a criminal tracking system, Locate Tracks in a

radar system •  Use Case Transac-ons

–  a use case transac-on as a "round trip" from the user to the system back to the user; a transac-on is finished when the system awaits a new input s-mulus.

–  In other words, in one transac-on the actor performs some ac-on which is input for the system. Then the system reacts; i.e., it processes the input and returns the result to the Actor.

Ho Tuong Vinh

So#ware Effort Es-ma-on With Use Case Points

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