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While it is true that carpeting should follow painting, it is not true that all painting must be completed before carpeting starts. The proper representation could be obtained by representing the activities as follows:

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Networks Level of Detail

A general guideline for determining the level of detail is that it must be keyed to the level of management using the network. Hierarchies of networks will be employed in more complex, large scale projects. A major aircraft design project, for example, might have three levels of networks.

The top-level network might summarize the ten major subdivisions of the project into 300 activities. The next level might involve describing each of the ten major project subdivisions with a network of 1,000 activities for a total of approximately 10,000 activities used in this intermediate level.

Each intermediate network could break down into ten l,000-activity networks employed at the actual operating level, resulting in a total of 100,000 activities being used at this most detailed level.

At any given level of management, there is always the question of how much detail is appropriate. Some organizations attempt to control level of detail by specifying that the network shall consist of a total number of activities ranging between X and Y.

This approach applied to projects of varying complexity can produce networks with widely varying levels of detail. A more sound approach to obtaining a consistent level of detail involves specifying that no more than X percent of the activities shall have a duration of more than Y or less then Z time periods.

Some more specific approaches to making level-of-detail decisions are:

1. For the resource entities being controlled by this management level, one activity should end and another start at the point where a different resource comes into use on a given work item. This might be the basis for deciding to use the three activities, Layout Site, Clear Site, and Grade Site rather than the single activity, Prepare Site.

2. If some other activity is dependent on the first portion of the activity in question but is not dependent on its full completion and the overlap amounts to as much as one of the time periods used in duration assignments, the activity in question should be divided into two activities at the point of dependence.

3. If there is considerable doubt left as to whether or not an activity should be broken down into more detail, one should remember that the network analyst can later combine activities without the project manager's assistance, but will require assistance to further subdivide activities.

Combining Sub-networks

No matter how involved and complex the project, the rules for combining activities and precedence information into a network still hold. Often with very large projects, whole subprojects are performed independently but simultaneously as a part of the overall project. It is then possible to network the subprojects to reduce the complexity and then combine these sub-networks. Contractors or managers in charge of the subprojects may then have their responsibilities scheduled separately.

Overall management's total network can correspond precisely to the sub-networks without requiring an overall network to be constructed separately. Under these circumstances, responsibilities are split out before the network is constructed instead of after, and the complexity of the network generation is reduced rather than increased.

Any interface activities are identified with unique symbols to mark the points where the networks rejoin. These activities on the overall network contain the corresponding activity numbers from all sub networks.

CPM Implementation Recommendations

The project management consultant must acquaint himself with the project objective before starting the construction of the network model. He may do this in any or all of the following ways:

1. Reading the specifications 2. Revising drawings

3. Looking at artists' concepts of finished product 4. Discussing the function of the end product 5. Seeing a similar end product in use.

Then, he determines the management objectives, discussing with the project manager the question of which of the following objectives should govern the project management system operation to:

1. Meet a deadline for project completion 2. Minimize project length

3. Minimize the sum of direct and indirect costs 4. Minimize the variation in resource requirements

5. Limit the maximum resource requirements of one or more resource types 6. Communicate project information to various levels of individuals concerned 7. Co-ordinate the project with interface groups

The consultant is now ready to undertake the networking of one of the alternative approaches to the project. Subdividing the project as discussed earlier is the first step which should be attempted.

After either arriving at subdivisions or determining that no reasonable basis for subdivision exists, the planner should obtain a summary narrative from the project manager describing the approach to this portion of the work. This narrative should be in the order of 5-15 minute discussion of the intended project plan.

The consultant is now ready to start networking. It is possible to proceed by eliciting responses from the project manager to the question, "What other activity must take place?", and putting the response on paper as an activity node.

In general, one should put activity descriptions, abbreviated if necessary, in the nodes rather than code letters or numbers referring to some separate list. The network should be a document that can be read directly. Reference to a coded list destroys the flow of logic that one should perceive when examining a network.

Precedence can be ignored at this time and the result will be a sprinkling of unconnected activities over the worksheet. Some activities are obviously near the start of the project and will likely be placed to the left of the sheet, just as activities likely to have few successors will be placed toward the right. It is not necessary, however, that any location rules be followed. Worksheets containing pre-printed or predrawn nodes will speed up the network building process.

There is reluctance on the part of many individuals to commit to even the most preliminary network. It must be emphasized that this first network will be re-drawn and eventually change forms and that the original network will be discarded. Even then, however, some project managers respond more readily if their tentative descriptions are placed in a list first, then put into the network format.

The network planner may well invest some time in listing activities purely for the purpose of getting the modeling process underway. The network planner should never attempt to indicate predecessors on the list, however. Precedence information is much more easily obtained by directly incorporating each bit of information into the network as it drawn. When the process of discovering activities begins to lag, it is desirable to turn to precedence identification, rather than try to identify 100% of the activities on the first pass. Precedence may be determined by asking this question with reference to the predecessor: "What activities cannot start until this activity is completed?" In the process of establishing precedence connections, additional activities will be discovered and redefinition of existing activities will become necessary.

This process should be continued until the project manager is unable to readily find additional precedence relationships. There will usually be some precedence relationships that are not found in this first phase, but these remaining ones can best be discovered during the duration/resource assignment phase.

Network planning differs from bar charting in that no time/resource concerns restrict the construction of a network. This time-free model tends to encourage the consideration of more alternatives than does the bar chart. When the planners begin to have difficulty in thinking of additional activities to place on the network, however, it is then time to consider activity durations and resource requirements.

As the activities are reviewed for time/resource requirements, additional activities and precedence relationships will be discovered and some existing ones changed.

At this point it will be helpful to have a draftsman or clerical assistant redraw the network, attempting to have predecessors to the left of successors and attempting to minimize the crossing of arrows.

It is impossible to avoid having some arrows crossing others, but a sense of flow of the work is best attained when these are minimized. The revised network is then ready for use in estimating time and resource requirements of each activity.

For some individuals and groups, the process of obtaining this basic network model will give new understanding of the nature of the project. In fact, an organization may find it desirable to go no further on its first attempt at network project management.

Such an approach might involve posting the network where the project manager can refer to it during meetings and shading in each arrow as the activity is completed.

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