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Software Cost, Effort,Time and H-resource Estimation: Introduction and COCOMO Model G.Berio.

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Presentazione sul tema: "Software Cost, Effort,Time and H-resource Estimation: Introduction and COCOMO Model G.Berio."— Transcript della presentazione:

1 Software Cost, Effort,Time and H-resource Estimation: Introduction and COCOMO Model G.Berio

2 Estimating Methods Price-to-win Analogy Expert judgement Algorithmic Models (may constraint other estimations)

3 What it is measured Effort (E): usually measured in Person-Month (PM) or Person- Year (PY) (Month and Year are working quantities, not calendar) LOC: lines of code; KLOC: kilo lines of code; DSI: delivered source instructions; KDSI: kilo delivered source instructions Productivity (L) L = LOC/E: lines of codes corresponding to a deployed effort Personal productivity (L p ): - maximal - lines of codes produced by a person per month (year) H-resources (P) P=E/T: average number of (full-time) persons delivering the effort E within time T (if E is in PM or PY) Cost=(Costhour*hoursmonth)*(#months*P) usually measured in Currency (Euro, Dollar etc.) = (Costhour*hoursmonth)*E (E in PM) Costhour, Costmonth: usually each category of personnel has a recognised cost per hour/per month

4 COCOMO: COnstructive COst MOdel Modes of Development (generic features of software and development) Level of the model(specific features ofsoftware and development) E,T in term of KLOC to be delivered (DKSI)

5 Organic Mode: features of software and development Small size – up to 50,000 lines of code small, in-house development team experienced in application area non-stringent specifications of function, performance, acceptance tests, interfaces minimal communication overhead stable development environment minimal schedule pressure existing, proven technology

6 Semi-detached Mode: features of software and development Large size – up to 300,000 lines of code mix of experienced and non-experienced team members in application domain and development environment mix of stringent and non-stringent specifications of function, performance, acceptance tests, interfaces moderate schedule pressure

7 Embedded Mode: features of software and development Any size Poor experience with the same type of software Stringent specifications of function, performance, acceptance tests, interfaces Rigid, formal quality standards Close development among hardware, software, and operational procedures Leading technology employed Strong schedule pressure

8 Organic Mode: Examples, E,T Standard engineering, scientific and business modeling systems

9 Semi-detached Mode: Examples, E,T Standard transaction processing systems New usual DBMS Innovative command & control systems for inventory and production

10 Embedded Mode: Examples, E,T Avionic software systems Large and complex transaction processing systems Real-time systems New operating systems

11 COCOMO (Basic): variabilità di E delle linee di codice KLOC 2.4 * KLOC * KLOC * KLOC

12 Intermediate COCOMO: E, T Modes of Development Level of the model 2.4, , , , , , 1.05 Range of C nominal effort

13 Intermediate COCOMO: C Product Attributes C1C2C3C1C2C3 VL very low L low N nominal H high VH very high XH extra high

14 Intermediate COCOMO: C Computer Attributes C4C5C6C7C4C5C6C7 Virtual machine = software likes DBMS, SO, Network, Middleware, VM and so on used to realise the requested software; platform or infrastructure are also applicable terms

15 Intermediate COCOMO: C Personnel Attributes C 8 C 9 C 10 C 11 C 12

16 Intermediate COCOMO: C Project Attributes C 13 C 14 C 15

17 Riepilogo Coefficienti C i del COCOMO

18 COCOMO Detailed Phase sensitive effort distribution on –Plans&requirements –Software design –Coding&test –Integration&test

19 Waterfall and COCOMO Waterfall milestones LCR = Lifecycle Concepts Review SRR = Software Requirements Review PDR = Product Design Review CDR = Critical Design Review (design walkthrough) UTC = Satisfaction of Unit Test Criteria SAR = Software acceptance review Plans & Requirements Product Design Detailed Design Code & Unit Test Deployme nt Operations & Maintenance Phase out LCRSRRPDR CDR UTC SAR Integration & Test Waterfall COCOMO Design EngineeringConstruction Architecture Design

20 Phase-sensitive Effort Distribution

21 COCOMO: Stime E,T KLOC anche per singolo modulo! E EE E E E E E E E E E EE E

22 Esempio COCOMO E PM (basic) Si può verificare il calcolo a

23 Divisione di Effort - Organic: COCOMO dettagliato

24 Divisione Tempo - Organic: COCOMO dettagliato

25 Effort e Tempo PM Si può verificare il calcolo a

26 Interpolazione Lineare (51-55)/(128-32)*(70-32)+55 y=mx+n Si può verificare il calcolo a

27 Convalida di COCOMO COCOMO è stato convalidato con i seguenti risultati: Tuttavia, se è presente un controllo di processo (basato su un archivio storico dei progetti passati) è possibile valutare l’applicabilità di COCOMO nell’organizzazione specifica (analisi Post-Mortem)

28 Ipotesi COCOMO Cioè si ipotizza solo il tempo di comprensione dei requisiti e non la loro definizione (si tratta di un modello di processo a cascata) PM Richiede la stima delle linee di codice da fornire (KDSI)

29 Stima delle linee di codice (LOC, KLOC, DSI, KDSI) La stima delle linee di codice può essere relativa all’intero codice da sviluppare oppure a singoli “pezzi di codice” I “pezzi di codice” cui può essere associata la stima possono essere definiti in base a –Casi d’uso, –Funzioni in un DFD, –Componenti singoli o package di un’architettura, –… via via che tali informazioni diventano disponibili durante lo sviluppo del software

30 Struttura dei Modelli Algoritmici di Costo effort = const+tuning coefficient * size exponent usually derived as person-months of effort required either a constant or a number derived based on complexity of project Software size in term of LOC (or FP) empirically derived


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