28. What are the advantages of Function Point Analysis (FPA) in relation to Use Case Points (UCP)?


Firs­tly, it is neces­sary to demys­tify that only the UCP tech­ni­que is sui­ta­ble for mea­su­ring sys­tems whose requi­re­ments are expres­sed through Use Cases. The Func­tion Point Analy­sis (FPA) can be used nor­mally to these situ­a­ti­ons as well as for mea­su­ring sys­tems whose requi­re­ments were docu­men­ted using a dif­fe­rent methodology.


Some advan­ta­ges of Func­tion Point Analy­sis over UCP are lis­ted below:


1. The UCP can only be applied on soft­ware pro­jects whose spe­ci­fi­ca­tion has been expres­sed by Use Cases. The mea­su­re­ment of Func­tion Point Analy­sis (FPA) is inde­pen­dent of how the soft­ware requi­re­ments were expres­sed. This advan­tage of the Func­tion Point Analy­sis (FPA) was cited by Gus­tav Kar­ner in his ori­gi­nal work “Resource Esti­ma­tion for Objec­tory Pro­jects” (1993).


2. It´s not pos­si­ble to apply the UCP in the mea­su­re­ment of exis­ting appli­ca­ti­ons whose docu­men­ta­tion is either out­da­ted or even don´t exist. The alter­na­tive would be to write the Use Cases for these appli­ca­ti­ons and then mea­sure it! But this would make the mea­su­re­ment imprac­ti­ca­ble, using a cost benefit analysis. Using the Func­tion Point Analy­sis (FPA) is pos­si­ble to per­form the mea­su­re­ment by analy­zing the actual appli­ca­tion in use.


3. There is not a sin­gle stan­dard for wri­ting Use Cases. Dif­fe­rent sty­les of wri­ting Use Case or on its gra­nu­la­rity can lead to dif­fe­rent results in mea­su­re­ment using UCP. The mea­su­re­ment by FPA of the Use Cases for a sys­tem will even­tu­ally reach the same result regar­dless the wri­ting style of the Use Cases or its gra­nu­la­rity, because Func­tion Point Analy­sis (FPA) “bre­aks” the requi­re­ment at the appro­pri­ate level for the mea­su­re­ment using the con­cept of Ele­men­tary Process.


4. Due to the pro­cess of mea­su­ring of the UCP being based on Use Cases, the method can­not be employed prior to com­ple­ting the analy­sis of requi­re­ments of the pro­ject. In most cases there is a need to get an esti­mate before the end of this step. Also, the Func­tion Point Analy­sis (FPA) pro­cess of mea­su­ring can only be used after the gathe­ring of the pro­ject requi­re­ments. But there are tech­ni­ques to esti­mate size in func­tion points that can be suc­ces­s­fully imple­men­ted before the requi­re­ments analy­sis is com­ple­ted. One exam­ple is the Indi­ca­tive and Esti­mate coun­ting pro­po­sed by NESMA. See the arti­cle Early Func­tion Points Count.


5. The UCP method does not include the mea­su­re­ment of soft­ware impro­ve­ment pro­jects (main­te­nance), only deve­lop­ment pro­jects. The Func­tion Point Analy­sis (FPA) addres­ses the mea­su­re­ment of deve­lop­ment pro­jects, impro­ve­ment pro­jects and appli­ca­ti­ons. These other types of mea­su­re­ment play an impor­tant role in metric pro­grams and in the hiring of soft­ware development.


6. There is no user group or orga­ni­za­tion res­pon­si­ble for the stan­dar­di­za­tion or evo­lu­tion of the UCP method, and the documentation about this sub­ject is scarce. There isn´t an offi­cial kno­wledge body on UCP. For Func­tion Point Analy­sis (FPA), the IFPUG is res­pon­si­ble for main­tai­ning the Coun­ting Prac­ti­ces Manual — the body of kno­wledge of the FPA, which is in con­ti­nu­ous evo­lu­tion. And there are also seve­ral dis­cus­sion forums about Func­tion Point Analy­sis (FPA) to exchange experiences.


7. The UCP method is not com­pli­ant with ISO/IEC 14.143 that defi­nes a model for the func­ti­o­nal mea­su­re­ment of soft­ware. The Func­tion Point Analy­sis (FPA), as the IFPUG manual, is stan­dar­di­zed under ISO/IEC 20926 as a method of func­ti­o­nal mea­su­ring, adhe­ring to ISO/IEC 14.143.


8. There isn’t a cer­ti­fi­ca­tion pro­gram of pro­fes­si­o­nals who know the PCU tech­ni­que and know how apply it appro­pri­a­tely. The IFPUG has CFPS cer­ti­fi­ca­tion pro­gram for the Func­tion Point Analy­sis (FPA).


9. The envi­ron­men­tal fac­tor inser­ted into the UCP com­pli­ca­tes its appli­ca­tion in soft­ware metrics pro­grams and ben­ch­mar­king between orga­ni­za­ti­ons, because it makes the size of a pro­ject vari­a­ble, without even chan­ging its func­ti­o­na­lity. If the same pro­ject is deli­ve­red to two dif­fe­rent teams to score points by Use Cases of this pro­ject, it will also be dif­fe­rent in each situ­a­tion. In order words, the same pro­ject has two sizes!


10. The UCP deter­mi­na­tion of tech­ni­cal and envi­ron­men­tal fac­tors is sub­ject to a cer­tain degree of sub­jec­ti­vity which in turn is dif­fi­cult to make the con­sis­tency of the method in dif­fe­rent orga­ni­za­ti­ons. The Func­tion Point Analy­sis (FPA) adjust­ment fac­tor also has the same pro­blem, although the IFPUG has spe­ci­fic gui­de­li­nes that help to mini­mize this impact. Howe­ver, the use of the adjust­ment fac­tor is opti­o­nal in the Func­tion Point Analy­sis (FPA) and the count of unad­jus­ted func­tion points is cur­ren­tly an objec­tive process.


Among the UCP disad­van­ta­ges quo­ted in rela­tion to Func­tion Point Analy­sis (FPA), some could be over­come with sim­ple adjust­ments. Howe­ver, there is no addi­ti­o­nal bene­fit of UCP over Func­tion Point Analy­sis (FPA). Using both methods would not com­pen­sate the addi­ti­o­nal cost of mea­su­re­ment and the effort to train the staff in the two methods.


Although Func­tion Point Analy­sis (FPA) is not a per­fect tech­ni­que, there is a great matu­rity in the mar­ket regar­ding its use and IFPUG works con­ti­nu­ously to its evolution.




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