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Software Size Estimation

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This presentation describes: - What is software size? - How to Measure Software size? - Techniques and parameters in Software Size estimation - Where and how to apply the techniques?

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Software Size Estimation
Software Size Estimation
Software Size Estimation An activity in software engineering that is used to estimate the size of a software application or component What is Software Size Estimation?
Size increases, the interdependency among various elements of the software grows rapidly increase.  “Software size is the main driver for project cost estimation” Why we feel need? Software Size Estimation
1) Initial sizing during or after requirements phase 2) Subsequent sizing after system design or when change occurs 3) Final sizing after install Define Design Build Test Implement Sizing Sizing Sizing When to Size Phases 1. Define 2. Design 3. Implement Software Size Estimation
The measurement of software size is hard. The Measurement of Software Size Why
Difference between Software sizing and software effort estimation?  Sizing estimates the probable size of a piece of software  while effort estimation predicts the effort needed to build it. Difference Software Sizing Vs Effort Estimation
The Measurement of Software Size Two methods of software size measurement  Functional size measurement method  Non-Functional size measurement method. Method How?
Functional size measurement methods Functional size measurement methods measure the functionality Advantages of functional size measurement methods  The size measurement is repeatable and verifiable.  The size measurement is defendable. Disadvantages of functional size measurement  Need Expert People.  It takes some time and costs effort Software Size Measurement Methods Functional Method (‘what does the software do’)
Non-functional size measurement methods  Measure the technical objects of the software  e.g Use-Case , DFD, Sequence diagram etc. Software Size Measurement Methods Non- Functional Method ( Diagrams )
The Software Size There are many techniques of software size estimation but here we will discuss only five techniques which are : 1. LOC (Line of code) 2. Functional Point (FP) 3. Wideband Delphi 4. Component Estimating 5. 3-point Estimation
The Software Sizing Techniques Types of LOC Two types of LOC 1) Physical LOC 2) Logical LOC Example 1. for (i = 0; i < 100; i++) printf("hello"); /* How many lines of code is this? */ 1. for (i = 0; i < 100; i++) { printf("hello"); } /* How many lines of code is this? */ LOC What is LOC ???
 Advantages of LOC 1. Automation of Counting 2. An Intuitive Metric  Disadvantage of LOC 1. Lack of Accountability 2. Lack of Cohesion with Functionality 3. Developer’s Experience 4. Difference in Languages 5. Problems with Multiple Languages 6. Lack of Counting Standards. The Software Sizing Techniques LOC (Analysis)
The Software Sizing Techniques An objective and structured technique to measure software size by quantifying its functionality provided to the user, based on the requirements and logical design. Function Point What is FP ?
Analysis Function Point The Software Sizing Techniques Function point Analysis consists of performing the following steps: • Determine the type of Function Point count • Determine the application boundary • Identify and rate to the Unadjusted Function Point count (UFP) • Identify and rate the data function types to calculate their contribution to the UFP • Determine the Value Adjustment Factor (VAF) by using General System Characteristics (GSCs) • Finally, calculate the adjusted Function Point count
Component Function Point The Software Sizing Techniques There are five component of FP: 1. EI’s (External Input) 2. EO’s (External output) 3. EQ’s (External inquiries) 4. EIF’s(External Interface Files) 5. ILF’s(Internal logical files)
Component Function Point The Software Sizing Techniques 1. External Input (EI) Is an elementary process in which data crosses the boundary from outside to inside 2. External Output (EO) An elementary process in which derived data passes across the boundary from inside to outside 3. External Inquiry (EQ) Is an elementary process with both input and output components that results in data retrieval from one or more internal logical files and external interface files
Component Function Point The Software Sizing Techniques 4. Internal Logical File (ILF) A user identifiable group of logically related data that resides entirely within the application boundary and is maintained through External Inputs 5. External Interface File (EIF) A user identifiable group of logically related data that is used for reference purposes only.
Rating the Transactional and Data Function Types Each of the identified components is assigned a rating (as Low, Average, and High) General System Characteristics (GSCs) The value adjustment factor (VAF) is calculated based on General System Characteristics that rate the general functionality of the application being counted • Rating the Transaction • Data Functi0n Types Function Point The Software Sizing Techniques
The degree of effect of each characteristic has to be determined as a rating on a scale of 0 to 5 as defined below. 0: Not present, or no effect 1: Incidental effect 2: Moderate effect 3: Average effect 4: Significant effect 5: Strong effect throughout General System Characteristics (GSCs) Degree of Effect Characteristic
General System Characteristics (GSCs) Once all the GSCs have been rated, TDI is obtained by summing up all the ratings. Now, Value Adjustment Factor is calculated using the formula: VAF = 0.65 + TDI/100 Final FP Count FP = Unadjusted Function Point count (UFP) * Value Adjustment Factor (VAF) Total Degrees of Influence (TDI)
Advantages: 1. Helps Comparison 2. Helps Monitor Scope Creep 3. Ease of Agreement Talks 4. Use of Historic Data Advantages & Disadvantages Function Points
Three steps for estimating the software Point Estimation Technique The Software Sizing Techniques In this technique we examine the three steps for estimating the software. Step1: work with the team member assigned to each task to identify both the positive and negative risks involved in their task. Step2: we ask the team member to make three estimates 1. BG 2. P 3. O Step3: mathematics with the three estimates the weighted mean=(O + 4BG + P) ÷ 6 the standard deviation= (P-O)/6
Delphi Estimating a way of attempting to get specialists in predicting software size to come to a consensus on their predictions - important because experts often disagree. How apply Delphi Technique ? 1. Group of experts [E1….Ei……En] 2. Meet to discuss project 3. Each estimates size:[X1….. Xi ….. Xn] 4. Each Ei __ gets to see all the Xs (anonymously) 5. Stop if the estimates are sufficiently close together 6. Otherwise, back to step 2 Wideband-Delphi Estimating Delphi Estimating is ?
Standard Component Estimation Technique guess the size of a software system as a function of the size estimates of its components. Apply Method • Gather historical data on key components • Guess how many of each type you will need (Mi) • Also guess largest (Li)_ and smallest (Si)_ extremes • Final estimate (Ei_) is a function of Mi,Li and Si • For example Ei=(Si+(4*Mi)+Li)/6 How to Apply ?

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Software Size Estimation

  • 3. Software Size Estimation An activity in software engineering that is used to estimate the size of a software application or component What is Software Size Estimation?
  • 4. Size increases, the interdependency among various elements of the software grows rapidly increase.  “Software size is the main driver for project cost estimation” Why we feel need? Software Size Estimation
  • 5. 1) Initial sizing during or after requirements phase 2) Subsequent sizing after system design or when change occurs 3) Final sizing after install Define Design Build Test Implement Sizing Sizing Sizing When to Size Phases 1. Define 2. Design 3. Implement Software Size Estimation
  • 6. The measurement of software size is hard. The Measurement of Software Size Why
  • 7. Difference between Software sizing and software effort estimation?  Sizing estimates the probable size of a piece of software  while effort estimation predicts the effort needed to build it. Difference Software Sizing Vs Effort Estimation
  • 8. The Measurement of Software Size Two methods of software size measurement  Functional size measurement method  Non-Functional size measurement method. Method How?
  • 9. Functional size measurement methods Functional size measurement methods measure the functionality Advantages of functional size measurement methods  The size measurement is repeatable and verifiable.  The size measurement is defendable. Disadvantages of functional size measurement  Need Expert People.  It takes some time and costs effort Software Size Measurement Methods Functional Method (‘what does the software do’)
  • 10. Non-functional size measurement methods  Measure the technical objects of the software  e.g Use-Case , DFD, Sequence diagram etc. Software Size Measurement Methods Non- Functional Method ( Diagrams )
  • 11. The Software Size There are many techniques of software size estimation but here we will discuss only five techniques which are : 1. LOC (Line of code) 2. Functional Point (FP) 3. Wideband Delphi 4. Component Estimating 5. 3-point Estimation
  • 12. The Software Sizing Techniques Types of LOC Two types of LOC 1) Physical LOC 2) Logical LOC Example 1. for (i = 0; i < 100; i++) printf("hello"); /* How many lines of code is this? */ 1. for (i = 0; i < 100; i++) { printf("hello"); } /* How many lines of code is this? */ LOC What is LOC ???
  • 13.  Advantages of LOC 1. Automation of Counting 2. An Intuitive Metric  Disadvantage of LOC 1. Lack of Accountability 2. Lack of Cohesion with Functionality 3. Developer’s Experience 4. Difference in Languages 5. Problems with Multiple Languages 6. Lack of Counting Standards. The Software Sizing Techniques LOC (Analysis)
  • 14. The Software Sizing Techniques An objective and structured technique to measure software size by quantifying its functionality provided to the user, based on the requirements and logical design. Function Point What is FP ?
  • 15. Analysis Function Point The Software Sizing Techniques Function point Analysis consists of performing the following steps: • Determine the type of Function Point count • Determine the application boundary • Identify and rate to the Unadjusted Function Point count (UFP) • Identify and rate the data function types to calculate their contribution to the UFP • Determine the Value Adjustment Factor (VAF) by using General System Characteristics (GSCs) • Finally, calculate the adjusted Function Point count
  • 16. Component Function Point The Software Sizing Techniques There are five component of FP: 1. EI’s (External Input) 2. EO’s (External output) 3. EQ’s (External inquiries) 4. EIF’s(External Interface Files) 5. ILF’s(Internal logical files)
  • 17. Component Function Point The Software Sizing Techniques 1. External Input (EI) Is an elementary process in which data crosses the boundary from outside to inside 2. External Output (EO) An elementary process in which derived data passes across the boundary from inside to outside 3. External Inquiry (EQ) Is an elementary process with both input and output components that results in data retrieval from one or more internal logical files and external interface files
  • 18. Component Function Point The Software Sizing Techniques 4. Internal Logical File (ILF) A user identifiable group of logically related data that resides entirely within the application boundary and is maintained through External Inputs 5. External Interface File (EIF) A user identifiable group of logically related data that is used for reference purposes only.
  • 19. Rating the Transactional and Data Function Types Each of the identified components is assigned a rating (as Low, Average, and High) General System Characteristics (GSCs) The value adjustment factor (VAF) is calculated based on General System Characteristics that rate the general functionality of the application being counted • Rating the Transaction • Data Functi0n Types Function Point The Software Sizing Techniques
  • 20. The degree of effect of each characteristic has to be determined as a rating on a scale of 0 to 5 as defined below. 0: Not present, or no effect 1: Incidental effect 2: Moderate effect 3: Average effect 4: Significant effect 5: Strong effect throughout General System Characteristics (GSCs) Degree of Effect Characteristic
  • 21. General System Characteristics (GSCs) Once all the GSCs have been rated, TDI is obtained by summing up all the ratings. Now, Value Adjustment Factor is calculated using the formula: VAF = 0.65 + TDI/100 Final FP Count FP = Unadjusted Function Point count (UFP) * Value Adjustment Factor (VAF) Total Degrees of Influence (TDI)
  • 22. Advantages: 1. Helps Comparison 2. Helps Monitor Scope Creep 3. Ease of Agreement Talks 4. Use of Historic Data Advantages & Disadvantages Function Points
  • 23. Three steps for estimating the software Point Estimation Technique The Software Sizing Techniques In this technique we examine the three steps for estimating the software. Step1: work with the team member assigned to each task to identify both the positive and negative risks involved in their task. Step2: we ask the team member to make three estimates 1. BG 2. P 3. O Step3: mathematics with the three estimates the weighted mean=(O + 4BG + P) ÷ 6 the standard deviation= (P-O)/6
  • 24. Delphi Estimating a way of attempting to get specialists in predicting software size to come to a consensus on their predictions - important because experts often disagree. How apply Delphi Technique ? 1. Group of experts [E1….Ei……En] 2. Meet to discuss project 3. Each estimates size:[X1….. Xi ….. Xn] 4. Each Ei __ gets to see all the Xs (anonymously) 5. Stop if the estimates are sufficiently close together 6. Otherwise, back to step 2 Wideband-Delphi Estimating Delphi Estimating is ?
  • 25. Standard Component Estimation Technique guess the size of a software system as a function of the size estimates of its components. Apply Method • Gather historical data on key components • Guess how many of each type you will need (Mi) • Also guess largest (Li)_ and smallest (Si)_ extremes • Final estimate (Ei_) is a function of Mi,Li and Si • For example Ei=(Si+(4*Mi)+Li)/6 How to Apply ?