FAST Function Points. David Seaver Director Estimation and Measurement Fidelity Investments

Transcription

1 FAST Function Points David Seaver Director Estimation and Measurement Fidelity Investments

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3 Outline of the Presentation Overview of function points (IFPUG based Technique) FAST Function Points Overview An example of a requirements based Function Point Count An example of a Screen based completed project Function Point Count

4 What is a Function Point Function Points measure software size by quantifying the functionality provided to the user based solely on logical design and functional specifications. With this in mind, the objectives of FP counting are to: measure functionality that the user requests and receives measure software development and maintenance rates and size independently of the technology used for implementation provide a normalizing measure across projects and organizations

5 What is Function Point? External Input Application Being Considered External Interface Files External Output External Inquiry Internal Logical File External Input External Output External Inquiry Other Applications Functionality as viewed from the user s perspective

6 How to Count Function Points

7 How to Count Function Points Displays Reports Master Files Size Control Files Reference Files Signals

8 Steps in FP Counting Determine Type of Count Identify Counting Scope and Application Boundary Count Data Functions Count Transactional Functions Determine Unadjusted Function Point Count Determine Value Adjustment Factor Calculate Adjusted Function Point Count

9 FP Overview: What Is Counted EI P1 Update Master File ILF Master File P2 Produce Weekly Report EO Weekly Summary Report Key Details EQ P3 Master File Details Reference File on another System EIF System Boundary

10 Data Storage Internal Logical File (ILF) Logical group of data maintained by the application (e.g., Employee file) External Interface File (EIF) Logical group of data referenced but not maintained (e.g., Global state table)

11 Transactions External Input (EI) Maintains ILF or passes control data into the application External Output (EO) Formatted data sent out of application with added value (e.g., calculated totals) External Query (EQ) Formatted data sent out of application without added value

12 Functional Size (Unadjusted Function Size) Function Type Low Average High EI x 3 x 4 x 6 EO x 4 x 5 x 7 EQ x 3 x 4 x 6 ILF x 7 x 10 x 15 EIF x 5 x 7 x 10

13 Value Adjustment Factor Based on 14 General System Characteristics (User Business Constraints Independent of Technology) Examples: data communications, response times, end user efficiency, multiple sites and flexibility Adjusts FP count by up to + / - 35%

14 Software Development Challenges Size of Requirements Changes to Requirements Estimation Based on Requirements Measuring and Improving Productivity and Quality

15 Size of Requirements Requirements Complete Business Terms Mutual Understanding Document Assumptions Size

16 Changes to Requirements Changes to Requirements Change Inevitable Trade-offs Customer Definition of Quality Size

17 Estimation Based on Requirements Estimation Based on Requirements Multiple Models Weighted Inputs: Language Skills Methodology Risk Factors Size Historical Base

18 Function Points Some Resources International Function Point Users Group International

19 Problems (real and alleged) with Function Points Takes a long time experienced counter can count 1500 function points a day Boring Cannot perform accurate count until design in reasonably complete Inconsistency

20 Function Points (My personal opinions) Core strength of the technique is the relationship it establishes between user transaction & data and software costs & schedules Very strong communication tool Proactively applied early in a project function points can accelerate the requirements and high level design process

21 Steps in FP Counting IFPUG Determine Type of Count Identify Counting Scope and Application Boundary Count Data Functions Count Transactional Functions Determine Unadjusted Function Point Count Determine Value Adjustment Factor Calculate Adjusted Function Point Count FAST Document Purpose of Estimate Identify Scope and Boundary Count Transactions Assign Data Functions to appropriate transactions Determine Unadjusted Function Point Count Determine Value Adjustment Factor Calculate Adjusted Function Point Count

22 How to Accelerate FP Counts Develop a profile of your Transactions and Data Functions Example Most of my use case have following attributes Create/new data function Edit No delete Edit or delete has an implicit inquiry Maintain 1 logical data group 1 report In function point speak 2 inputs add/edit 1 inquiry 1 file 1 ouput

23 How to Accelerate FP Counts Develop a profile of your typical complexity outputs are medium 5 Function Points inputs are low 3 Function Points inquiries are low 3 Function Points files are low 7 Function Points external interface files are not found 0 Function Points For my typical Use Case 2 inputs 6 Function Points 1 inquiry 3 Function Points 1 output 5 Function Points 1 File 7 Function Points General System Characteristics =1.12 AFP =23.52 round up to 24 Function Points for each use case

24 Accelerate Function Point Counts Take advantage of available Data ISBGS has average complexity numbers for the projects in the data base (700) Also have product delivery rate data for industry and platform PDR = hour/function point Platform Mainframe Midrange PC Useful as a inexpensive benchmarking tool

25 Accelerate Function Point Counts Low Average High ISBGS inputs outputs queries files xfiles Low, Average and High are the IFPUG values for Transactions and Data Functions Values in ISBGS column are the average values for the Transaction and Data Functions from the International Software Benchmarking Groups Database of projects

26 Estimating Examples Cost Categories BSV PPI SRA Function Points ,436 total hours 947 8,859 15,788 Total Cost $ 99,481 $ 885,876 $ 1,578,803 rate/hour person months person years Defects FP/PM Project Start 6/1/00 6/1/00 6/1/00 SRA/PPI Complete 6/10/00 7/25/00 8/8/00 TSD Complete 8/1/00 11/21/00 1/4/01 TPD Complete 9/7/00 2/14/01 4/21/01 SIT Complete 9/7/00 2/14/01 4/21/01 System Test Complete 9/21/00 3/24/01 6/7/01 Install Complete 9/27/00 4/8/01 6/25/01 Management wants to know how cost went from $100K to $1.5M You can use function points to explain what happened You can use function points to get approval of what's happening before you get into trouble

27 Function Point Count at BSV BSV Estimate Name inputs outputs inquiries files ex files Index Note inputs outputs inquiries files ex files maintain core personnel data data elements, add, edit, delete online help maintain users access data Simple project, administer 35 data elements for all employees in the company, simple GUI, online help, maintain user access for security reasons Total of 93 Function Points Created from system context diagram

28 Assumption Made to Generate Estimate System developed in Oracle Team has completed several Oracle Projects Team has completed several projects of this type Team has experience in this industry Requirements are stable

29 Estimate At BSV Function Points BSV Estimate Defects/ Function Points/ Function Hours Points Activity Requirements Analysis Preliminary Design System Designers/ Analysts Programmers Test Engrs. Project Mgt. QA/ CM Tech Pubs Total Hours Activity Length (Days) Start Dates End Dates /1/2000 6/10/ /2/2000 6/30/2000 Detail Design /7/2000 8/1/2000 Code and Unit Test /21/2000 8/18/2000 Integration and Test /27/2000 9/7/2000 System Integn & Test /1/2000 9/21/2000 Installation /27/2000 9/27/2000 Total /1/2000 9/27/2000

30 Function Point Count at SRA SRA Size Estimate Name inputs outputs inquiries files ex files Index Note inputs outputs inquiries files ex files maintain core personnel data data elements, add,edit,delete online help maintain users access data add 4 other data types support 5 different data feed formats international data differences UK Japan Germany China Data Providers data providers Data Consumers data consumers

31 Assumption Made to Generate Estimate System developed in Oracle Team has completed several Oracle Projects Team has completed several projects of this type Team has experience in this industry Requirements are stable?

32 Estimate At SRA Function Points Defects/ Function Points FP/Person Month SRA Estimate Activity System Designers/ Analysts Prog. Test Engrs. Project Mgt. QA/ CM Tech Pubs Total Hours Activity Length (Days) Start Dates End Dates Requirements Analysis /1/2000 7/25/2000 Preliminary Design /19/2000 9/9/2000 Detail Design /26/ /21/2000 Code and Unit Test /17/ /30/2000 Integration and Test /18/2000 2/14/2001 System Integn & Test /1/2000 3/24/2001 Installation /27/2000 4/8/2001 Total /1/2000 4/8/2001

33 Function Point Count at SDS Name inputs outputs inquiries files ex files Reference Note inputs outputs inquiries files ex files Data Encryption 5 5 encryp any standard phone inputs if international Ad HOC report Writer error notification 14 initial error notification and correction notification data push initiate data correction to providers data pull initiate data correction from consumers

34 Assumption Made to Generate Estimate System developed in Oracle Team has completed several Oracle Projects Team has completed several projects of this type Team has experience in this industry Requirements are stable?

35 Estimate At SDS Function Points Defects/ Function Points FP/Person Month 1, SDS Estimate Activity System Designers/ Analysts Programmers Test Engrs. Project Mgt. QA/ CM Activity Tech Pubs Total Hours Length (Days) Start Dates End Dates Requirements Analysis /1/2000 8/8/2000 Preliminary Design /26/ /4/2000 Detail Design /12/2000 1/4/2001 Code and Unit Test /13/2000 2/21/2001 Integration and Test /21/2000 4/21/2001 System Integn & Test /1/2000 6/7/2001 Installation /3/2000 6/25/2001 Total /1/2000 6/25/2001

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44 Function Points for Estimate Tab Name inputs outputs inquiries files interfaces Index Note inputs outputs inquiries files interfaces Model Equation Increment Phasing Increment Breakage Labor Cost APM MN APM Description

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57 Name inputs outputs inquiries files interfaces Me Note inputs outputs inquiries files interfaces New Estimate Open Estimate Save Estimate Save Estimate As Copy Estimate Close Estimate Load Model Import Comands Save Commands as Exit Component List Component Tree View Estimate List Window List Create Component Window Close Reports for Other Estimates Close All Reports Reports Constrain Project Set Default Model Start with empty estimate reset preferences Help

58 Function Points for COSTAR Function Points Component # Component Name Component Summary inputs outputs inquiries files interfaces 1 Estimate TAB Component 2 TAB Menu Items Total