Soft test review - 05- Software Engineering Software Project Estimation & Scheduling Management

Software Project Estimation

Common estimation methods:

1. Estimate based on similar projects have been completed.
2. Estimated based on the decomposition technology plan.
3. Estimate empirical estimation model.

Cost Estimation

1. Top-down : the completion of the project from the previous assembly had now estimate the total cost and then distributed.
2. Bottom-up : first estimated separately for each development effort needed to think, and finally is added.
3. Difference estimation method : the project will be developed with the ratio of completed projects, to find out where the difference lies, and to estimate the impact of the cost for each difference.
4. Experts estimate method
5. Class conjecture algorithm
6. Equation estimation method

COCOMO model estimates

Is an accurate, easy-to-use static cost estimation model.
Basic COCOMO model:

Intermediate COCOMO model

COCOMOII model

Also estimate the model hierarchy is divided into three stages model.

1. Application assembly model. In the early use of software engineering.
2. Early design stage model. On the demand has stabilized and is used to establish grass-roots system software architecture views.
3. Stage model architecture. Use the software build process.

Putnam estimation model

It is a dynamic multi-variable model, assuming that there is a specific workload distribution throughout the life cycle of software development.

Schedule Management

Software Project Management software aims to ensure the project is completed on schedule within the stipulated time. A software project can usually be divided into multiple sub-projects and tasks, there is a relationship between these tasks. Project management and task is to define dependencies between all project tasks, develop scheduling of the project, the planning effort and duration required for each task, and track adjustments in the development process.

The basic principle

1. Division. That product and process decomposition.
2. Interdependencies. After the division since the relationship between the various activities or tasks must be clear.
3. time management. Must allocate a certain amount for each scheduled task work units, you must develop start and end times for each task.
4. Workload confirmation. Each project has a predetermined number of personnel involved.
5. Determine responsibility.
6. Clear output. We arranged a schedule for each task should be enough to have a clear output.
7. Set milestones.

Scheduling

Common graphic description of the method of scheduling there Gantt (Gantt) charts and project PERT (Program Evaluation & Review Technique, PERT) chart.

Gantt chart

Is a simple horizontal bar chart, he described the calendar as a benchmark project tasks. The horizontal axis represents the time line, each bar representative of a task. On the left is the task name, start and end of the horizontal bar corresponds to the time required for the task.

Gantt chart can clearly describe each task when to start, when the end of the parallel between the progress of the task, and each task. But not clearly reflect the dependencies between the various tasks, it is difficult to determine the key to the whole project, it can not reflect the plan has the potential part.

PERT chart

Is a directed graph, arrows in the drawing indicates that the task, the task can be completed on time required superscript, FIG node represents the start and end of the next task on the task of a node, called an event. The event itself does not consume any resources, only that point in time.

• The first time: this means that the task before the time of departure from the event can not start.
• At the latest time: starting from the event task must start before this time.
• Relaxation time: to complete the task without affecting the duration of how much room to maneuver. Relaxation time is 0 path is a critical path to complete the rectification works.

As shown, each amount calculated as follows:

• The minimum time (critical path): and complete the task of drawing the longest path.
• The earliest start time: up to a certain input and flow of the project before the start point.
• Latest Start Time: Critical Path - from the start point to the end point of the last of the entire project (if multiple paths, select the minimum piece).
• Earliest finish time: up to enter and flow of a certain point before the end of the project.
• Latest end time: the critical path - the end point of the distance (selected minimum) final end point of the whole project.
• Relaxation time: latest start time - earliest start time.
• Relaxation time: no later than the end of time - the earliest end time.
• Relaxation time: the critical path - the longest path of the required activities.

Example: Based on the graph, the critical path is determined and FG relaxation time
calculated critical path :
First, calculate the respective path length:
1.ABEGJ:. 3. 7 + 15 + 2 + 27 =
2.ACFGJ:. 3. 6 + + +. 7. 4 20 is =
3.ACFHJ:. 6. 4 + = 40 + 10 + 20 is
4.ADFGJ: + 10. 8. 7 = + 28. 3 +
5.ADFHJ:. 8 + 10 + 10 = 48 + 20 is
6.ADFIHJ: + 10 +. 8. 4 10 = 32 +
7.ADFIJ: + 10 + 8 = 34 is. 4 + 12 is
the longest of the heald 48, 48 so that a minimum time is
calculated relaxation time of the FG:
according to the above formula, were calculated:
the earliest start: 10 + 8 18 =
latest start: 48-3-7 = 38
earliest end: 10 = 21 + 8 + 3
latest end: 48-7 = 41
stars relaxation time: 38-18 or 41-21 = 20 = 20