CS3773 Software Engineering

Lecture 8Software Planning and

Estimation

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Software Management

Software engineering is a managed process – People management – Software cost estimation– Quality management– Configuration management

Software management activities may include– Proposal writing– Software planning– Project monitoring – Personnel selection and evaluation

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Software Planning

Effective software management depends on thoroughly planning the progress of the project

Project planning identifies the activities, milestones, and deliverables produced by a project

Project plan guides the development towards the project goals

In planning, cost estimation is an important task, which is concerned with estimating the resources required to accomplish the project plan

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Project Plan

Project plan shall include the following sections– Introduction– Project organization – Risk analysis– Hardware and software resource requirements– Work breakdown– Project schedule– Monitoring and reporting mechanism

Project plan is revised during project development

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Milestones and Deliverables

A milestone is a recognizable end-point of a software process activity

– Deliverables are milestones Requirements specification Architectural design Program

– Internal project results that are used by the project manager to check project progress are milestones

Software process must be broken down into basic activities with associated outputs to establish milestones

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Project Scheduling

Project scheduling separates the total work involved in a project into separate activities and judging the time required to complete them

Project scheduling organizes all the activities into a coherent order

– Some of the activities can be carried out in parallel– Some of the activities must be organized in a sequential

manner– Project activities shall last lat least a week

Project schedules are usually represented as a set of charts or diagrams

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Mechanics of Scheduling

We follow the three steps to produce a project schedule

– Decomposing activities into subtasks and estimating the

durations - produce an estimation table

– Identifying dependencies on subtasks – produce a priority

graph

– Assigning subtasks and analyzing resulting schedule –

produce a critical path diagram

Project schedule charts or diagrams show work

breakdowns, activities dependencies, and staff

allocations

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Estimation Table

Task Names Duration (days) Accumulated Duration *

IT1 3 3

IT2 5 8

IT3 4 12

IT4 4 16

IT5 7 23

IT6 2 25

* We assume that the project is done by a single developer

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Priority Graph

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Critical Path Method (CPM)

CPM take as input – Estimation table– Priority graph– An assignment of each task to a programmer– An ordering on the tasks assigned to each programmer

It computes – Earliest start time of each task– Earliest completion time for all tasks– Slack time, the amount of time starting on a task can be

delayed without affecting the earliest completion date

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CPM: Notational Convention for Tasks

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CPM: Ordering of Constraints

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CPM Example

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CPM Example

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CPM Example

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CPM Example

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CPM Example

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CPM Example

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Gantt Charts

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Reading Assignments

Sommerville’s Book, 8th edition – Chapter 5, “Project Management”

Sommerville’s Book, 9th edition – Chapter 22, “Project Management”– Chapter 23, “Project Planning”