Overview

• Software planning involves estimating how much time, effort, money, and resources will be required to build a specific software system. After the project scope is determined and the problem is decomposed into smaller problems, software managers use historical project data (as well as personal experience and intuition) to determine estimates for each. The final estimates are typically adjusted by taking project complexity and risk into account. The resulting work product is called a project management plan.

Estimation Reliability Factors

• Project complexity
• Project size
• Degree of structural uncertainty (degree to which requirements have solidified, the ease with which functions can be compartmentalized, and the hierarchical nature of the information processed)
• Availability of historical information

Project Planning Objectives

• To provide a framework that enables software manager to make a reasonable estimate of resources, cost, and schedule.
• Project outcomes should be bounded by 'best case' and 'worst case' scenarios.
• Estimates should be updated as the project progresses.

Software Scope

• Describes the data to be processed and produced, control parameters, function, performance, constraints, external interfaces, and reliability.
• Often functions described in the software scope statement are refined to allow for better estimates of cost and schedule.

Customer Communication and Scope

• Determine the customer's overall goals for the proposed system and any expected benefits.
• Determine the customer's perceptions concerning the nature if a good solution to the problem.
• Evaluate the effectiveness of the customer meeting.

Feasibility

• Technical feasibility is not a good enough reason to build a product.
• The product must meet the customer's needs and not be available as an off-the-shelf purchase.

Estimation of Resources

• Human Resources (number of people required and skills needed to complete the development project)
• Reusable Software Resources (off-the-shelf components, full-experience components, partial-experience components, new components)
• Development Environment (hardware and software required to be accessible by software team during the development process)

Software Project Estimation Options

• Delay estimation until late in the project.
• Base estimates on similar projects already completed.
• Use simple decomposition techniques to estimate project cost and effort.
• Use empirical models for software cost and effort estimation.
• Automated tools may assist with project decomposition and estimation.

Decomposition Techniques

• Software sizing (fuzzy logic, function point, standard component, change)
• Problem-based estimation (using LOC decomposition focuses on software functions, using FP decomposition focuses on information domain characteristics)
• Process-based estimation (decomposition based on tasks required to complete the software process framework)

Empirical Estimation Models

• Typically derived from regression analysis of historical software project data with estimated person-months as the dependent variable and KLOC or FP as independent variables.
• Constructive Cost Model (COCOMO) is an example of a static estimation model.
• The Software Equation is an example of a dynamic estimation model.

Make-Buy Decision

• It may be more cost effective to acquire a piece of software rather than develop it.
• Decision tree analysis provides a systematic way to sort through the make-buy decision.
• As a rule outsourcing software development requires more skillful management than does in-house development of the same product.

Automated Estimation Tool Capabilities

• Sizing of project deliverables
• Selecting project activities
• Predicting staffing levels
• Predicting software effort
• Predicting software cost
• Predicting software schedule