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The relationships between each task and the cost of every task are made based on the historical engineering experience.

Part 2: Schedule Management & Control
3. Overview of Schedule Management Tools
3.1 Work Breakdown Structure (WBS)
Work breakdown structure (WBS) is a hierarchical representation of the work contents. It is proved to be efficient that using WBS to define and structure the project works. WBS for now is a common tool in project management as the Project Management Book of Knowledge (PMBOK) collected the word and redefined it. According PMBOK’s describe, WBS is a deliverable oriented hierarchical decomposition of the work to be executed by the project team (PMI, 2008). Through WBS, the project can be subdivided into smaller parts in order to let project managers or other workers clear about the components of the project. And also, it can make a great contribution to operate procedure standardization.

The importance of Work Breakdown Structure has been acknowledged by both theoretical researchers and engineering practice personnel. First of all, tt is the basis for defining work packages which is the crucial work of project management preparation (Rad, 1999; Colenso, 2000). Garcia-Forniels et al. (2003) declared that the WBS is the most important tool for project management because it provides a basis for scheduling, planning, responsibility assignment, information management and control. Also, through the procedure of WBS, the construction project information can be collected by the computer. Thus the WBS is the fundamental of project informationize.

Being a kind of scientific methodology of project management, the process of decomposition lead by WBS is not arbitrary but according to a sequence of principles and standards. There are 3 most important pre-works need to complete before project managers initiate the WBS process. The first relates to the decomposition criteria, which reflect the facets of information by which the work is subdivided across the WBS hierarchy. The second is the sequencing of these criteria, which relates to the order in which the criteria are applied in the hierarchy. The third issue relates to the level of detail, which reflects the extent to which the entire work is decomposed.

Meanwhile, there are another 3 principles should be followed:
1) Each hierarchy should be a complete reflection of the whole project.
2) Different hierarchy should have different standard when decomposition.
3) The amount of hierarchies should stay at a proper level that those tasks in the lowest hierarchy can be precisely evaluated.

3.2 Gantt Chart
Gantt chart is invented by Henry Laurence Gantt in 1917. The form of Gantt chart is a kind of bar diagram. In the bar diagram, the horizontal axis represents for the duration and the vertical axis represents for those tasks in the project. The horizontal bar in the chart gives a visual image to readers to understand the condition of each task. The length of the horizontal bar can show how long the task should spend; the start and the end of the bar represent the time point of the task starts and ends. Gantt chart is composed by task duration, line of relationship attachment and time scale.

Gantt chart is used widely in project management. According to the describe of Gantt chart which is stated before, the biggest