3 Software Estmation.ppt
- 2. Learning Objectives By the end of the lecture you should be able to: Understand the concept of Size and Cost estimation of SW Comprehend various methods like LoC counting Function Point counting and Work Break down structure Explain various best practices around SW Estimation 2
- 3. Cost Estimation project scope must be explicitly defined task and/or functional decomposition is necessary historical measures (metrics) are very helpful at least two different techniques should be used or two persons doing it remember that uncertainty is inherent
- 4. Estimation Techniques past (similar) project experience conventional estimation techniques Work breakdown and effort estimates size (e.g. FP) estimates
- 5. Functional Decomposition Statement of Scope perform a "grammatical parse" functional decomposition
- 6. Creating a Task Matrix Obtained from process framework application functions framework activities Effort required to accomplish each framework activity for each application function
- 7. Conventional Methods: LOC/FP Approach compute LOC/FP using estimates of information domain values use historical effort for the project
- 8. Example: LOC Approach Functions UICF 2DGA 3DGA DSM CGDF PCF DAM Totals estimated LOC $/LOC Cost Effort (months) LOC/pm 2340 5380 6800 3350 4950 2140 8400 33,360 14 20 20 18 22 28 18 315 220 220 240 200 140 300 32,000 107,000 136,000 60,000 109,000 60,000 151,000 655,000 7.4 24.4 30.9 13.9 24.7 15.2 28.0 145.0
- 9. Function Point - Constituents External Inputs (EI) - is an elementary process in which data crosses the boundary from outside to inside. This data may come from a data input screen or an other application. The data is used to maintain one or more internal logical files. A good source of information to determine EIs are Screen Layouts, Screen Formats & dialogs, and layouts of any input forms. Additional inputs from other applications should be inventoried here. Inputs from other applications must update ILFs of application being counted.
- 10. Function Point - Constituents External Outputs (EO) - an elementary process in which derived data passes across the boundary from inside to outside. The data creates reports or output files sent to other applications. These reports and files are created from one or more Internal Logical Files A good source of information to determine the EOs are report layouts and electronic file formats that are being sent outside the application boundary. Additionally, an EO may update an ILF.
- 11. Function Point - Constituents External Inquiries (EQ) - an elementary process with both input and output components that result in data retrieval from one or more Internal Logical Files. The input process does not update any Internal Logical Files, and the output side does not contain derived data. A good source of information to determine the External Inputs (EIs) are Screen Layouts, Screen Formats & dialogs, and layouts of any input forms.
- 12. Function Point - Constituents Internal Logical Files (ILF) - a user identifiable group of logically related data that resides entirely within the applications boundary and is maintained through External Inputs. A good source of information to determine the ILFs are logical and/or preliminary physical data models, table layouts, data base descriptions. External Interface Files (EIF) - a user identifiable group of logically related data that is used for reference purposes only. The data resides entirely outside the application and is maintained by another application. The External Interface File is an Internal Logical File for another application. The External Interface File is an Internal Logical File for another application. A good source of information to determine EIFs are interfaces descriptions with other systems.
- 13. Function Point - Counting After the components have been classified as one of the five major components (EIs, EOs, EQs, ILFs or EIFs), a ranking of low, average or high is assigned. For transactions (EIs, EOs, EQs) the ranking is based upon the number of files updated or referenced (FTRs) and the number of data element types (DETs). For both ILFs and EIFs files the ranking is based upon record element types (RETs) and data element types (DETs). ILF and EIF
- 14. Taking Complexity into Account Sl General System Characteristic Brief Description 1 Data communications How many communication facilities are there to aid in the transfer or exchange of information with the application or system? 2. Distributed data processing How are distributed data and processing functions handled? 3. Performance Was response time or throughput required by the user? 4. Heavily used configuration How heavily used is the current hardware platform where the application will be executed? 5. Transaction rate How frequently are transactions executed daily, weekly, monthly, etc.? 6. On-Line data entry What percentage of the information is entered On-Line? 7. End-user efficiency Was the application designed for end-user efficiency? 8. On-Line update How many ILFs are updated by On-Line transaction? 9. Complex processing Does the application have extensive logical or mathematical processing? 10. Reusability Was the application developed to meet one or many users needs? 11. Installation ease How difficult is conversion and installation? 12. Operational ease How effective and/or automated are start-up, back-up, and recovery procedures? 13. Multiple sites Was the application specifically designed, developed, and supported to be installed at multiple sites for multiple organizations? 14. Facilitate change Was the application specifically designed, developed, and supported to facilitate change?
- 16. Example: FP Approach number of user inputs number of user outputs number of user inquiries number of files number of ext.interfaces algorithms measurement parameter 4 5 4 7 7 3 count x x x x x x count-total = = = = = = weight complexity multiplier feature points 0.25 p-m / FP = 120 p-m 40 25 12 4 4 60 160 125 48 28 28 180 569 .84 478
- 17. Analyzing the Information Domain complexity multiplier function points number of user inputs number of user outputs number of user inquiries number of files number of ext.interfaces measurement parameter 3 4 3 7 5 count weighting factor simple avg. complex 4 5 4 10 7 6 7 6 15 10 = = = = = count-total X X X X X
- 18. Why Opt for FP Measures? independent of programming language uses readily countable characteristics of the "information domain" of the problem does not "penalize" inventive implementations that require fewer LOC than others makes it easier to accommodate reuse and the trend toward object-oriented approaches But many a times its too early to count DETs, RETs and FTRs
- 19. Estimation Guidelines estimate using at least two techniques get estimates from independent sources avoid over-optimism, assume difficulties you've arrived at an estimate adjust for the people who'll be doing the jobthey have the highest impact Organizational capability should be baselined esp effort per FP or effort per KLoC
- 21. Make or Buy (path probability) x (estimated path cost) i i For example, the expected cost to build is: expected cost = 0.30($380K)+0.70($450K) similarly, expected cost = $382K expected cost = $267K expected cost = $410K build reuse buy contr expected cost = = $429 K
- 22. Case Study for FP counting The Institute wants to develop an automated Examination Tracking System. There are four semesters in MBA and at the end of each semester, there are written examinations. Student attendance for exam is recorded through swiping of ID card. After the exam, papers are sent to respective examiners for evaluation and marks are recorded. The candidates should be able to download their marksheet. Successful candidates can download their semestral certificates also. The criteria for success are to obtain 40% in each subject and 50% on aggregate. The system is expected to generate the following reports: Attendance details / summary for each subject in each semester Performance details / summary for each subject in each semester 22