Ch. 6

Burst Activity

An activity that has more than one activity immediately following it. When working backwards, the LF of a Burst Activity is the smallest LS of the successor activities.

Predecessor Activity

An activity that logically comes before a dependent activity in a schedule. All Predecessor Activities must be completed before their Merge Activity can begin.

Early Finish

Top Right Corner of Legend Calculated as: EF = ES + DUR or 0 +10

Project Network

A flow chart that graphically depicts the sequence, interdependencies, and start and finish times of the project job plan of activities that is the critical path through the network.

Hammock Activity

A group of related schedule activities aggregated and displayed as a single activity. Key benefit of Hammock Activity: Assignment and Control of Indirect Costs. The goal is to simplify control and Mgmt. by combining tasks.

Forward Pass

Answers questions: How soon can the activity start? (early start—ES) How soon can the activity finish? (early finish—EF) How soon can the project be finished? (expected time—TE) The forward pass starts with the first project activity(ies) and traces each path (chain of sequential activities) through the network to the last project activity(ies). As you trace along the path, you add the activity times. Remember: You add activity times along each path in the network (ES + DUR = EF). You carry the early finish (EF) to the next activity where it becomes its early start (ES), or If the next succeeding activity is a merge activity, you select the largest early finish number (EF) of all its immediate predecessor activities. The forward pass begins with the project start time, which is usually time zero.

Gnatt Chart

Bar charts are popular because they present an easy-to-understand, clear picture on a time-scaled horizon. They are used during planning, resource scheduling, and status reporting. Unfortunately, when projects have many dependency relationships, the dependency lines soon become overwhelming and defeat the simplicity of the Gantt chart.

Backward Pass

Before the backward pass can be computed, the late finish for the last project activity(ies) must be selected. In early planning stages, this time is usually set equal to the early finish (EF) of the last project activity (or in the case of multiple finish activities, the activity with the largest EF). In some cases an imposed project duration deadline exists, and this date will be used. How late can the activity start? (late start—LS) How late can the activity finish? (late finish—LF) Which activities represent the critical path (CP)? This is the longest path in the network which, when delayed, will delay the project. How long can the activity be delayed? (slack or float—SL) The backward pass starts with the last project activity(ies) on the network. You trace backward on each path subtracting activity times to find the late start (LS) and late finish (LF) times for each activity. Before the backward pass can be computed, the late finish for the last project activity(ies) must be selected. Remember: You subtract activity times along each path starting with the project end activity (LF − DUR = LS). You carry the LS to the preceding activity to establish its LF, or If the next preceding activity is a burst activity; in this case you select the smallest LS of all its immediate successor activities to establish its LF.

Activity Time Estimate/DUR

Bottom Middle of Legend

Networks

Built using nodes (boxes) and arrows (lines)

Early Times vs. Late Times

Early Times: The earliest the project can start or finish based on network logic, the data date, and any schedule constraints. Late Times: The latest an activity can start or finish without delaying the completion of the project. ES: Top Left of Legend LF: Bottom Left of Legend

Free Slack

Free slack (FS) The maximum amount of time an activity can be delayed from its early start (ES) without affecting the early start (ES) of any activity immediately following it. FS is unique. It is the amount of time an activity can be delayed without delaying any immediately following (successor) activity. Or, free slack is the amount of time an activity can exceed its early finish date without affecting the early start date of any successor(s). Free slack can never be negative. Only activities that occur at the end of a chain of activities, where you have a merge activity, can have free slack. LF-EF = SL LS-ES = SL SL = Middle Right Column of Legend

Mgmt. process fails when:

Integrating the work packages and the network, because (1) different groups (people) are used to define work packages and activities and (2) the WBS is poorly constructed and not deliverable/output oriented.

Activity

Part of the network that consumes time, ex: working or waiting. Are built out of and around work packages from WBS. Activities are placed in a sequence that provides for orderly completion of the Project. *Requires Time but not necessarily resources.

Dangler Paths

Some computer programs require a common start and finish event in the form of a node—usually a circle or rectangle—for a project network. Even if this is not a requirement, it is a good idea because it avoids "dangler" paths. Dangler paths give the impression that the project does not have a clear beginning or ending. If a project has more than one activity that can begin when the project is to start, each path is a dangler path. The same is true if a project network ends with more than one activity; these unconnected paths are also called danglers. Danglers can be avoided by tying dangler activities to a common project start or finish node.

Lag

Synonymous with delay. A lag is the minimum amount of time a dependent activity must be delayed to begin or end. The use of lags in project networks occurs for two primary reasons: When activities of long duration delay the start or finish of successor activities, the network designer normally breaks the activity into smaller activities to avoid the long delay of the successor activity. Use of lags can avoid such delays and reduce network detail. Lags can be used to constrain the start and finish of an activity.

Finish-to-Finish Relationship

The finish of one activity depends on the finish of another activity

Critical Path

The longest path through a network diagram that determines the earliest completion of a project. Based on finding the series activities, from start to finish, with the minimum (usually zero) slack. Increasing lag on a critical path is the same as increasing duration.

The Manager:

The manager derives activity time estimates from the task times in the work package

Finish-to-Start Relationship

The most common precedence relationship is when one activity cannot start until another activity has finished. In most schedules this is the relationship that exists in almost all (if not all) cases. This is referred to as a Finish-to-Start relationship. For example, it may take 1 day to place orders but take 19 days to receive the goods. The use of finish-to-start allows the activity duration to be only 1 day and the lag 19 days. This approach ensures the activity cost is tied to placing the order only rather than charging the activity for 20 days of work.

Start-to-Start Relationship

The start-to-start relationship reduces network detail and project delays by using lag relationships. 2nd most common precedence relationship. Typically combined with Finish-to-Finish

Parallel activity

These are activities that can take place at the same time, if the manager wishes. However, the manager may choose to have parallel activities not occur simultaneously.

Merge Activity

This is an activity that has more than one activity immediately preceding it (more than one dependency arrow flowing to it).

Total slack

Total Slack = (TS) The amount of time an activity can be delayed and not affect the project duration (TS = LS − ES or LF − EF). TS tells us the amount of time an activity can be delayed and not delay the project. Stated differently, total slack is the amount of time an activity can exceed its early finish date without affecting the project end date or an imposed completion date. Relates to the project end date while Free Slack (FS) related to the successor next (next) activity start date.

Laddering

Under the standard finish-to-start relationship, when an activity has a long duration and will delay the start of an activity immediately following it, the activity can be broken into segments and the network drawn using a laddering approach so the following activity can begin sooner and not delay the work.

Sensitivity

We use the term sensitivity to reflect the likelihood the original critical path(s) will change once the project is initiated. Sensitivity is a function of the number of critical or near-critical paths. A network schedule that has only one critical path and noncritical activities that enjoy significant slack would be labeled insensitive. Conversely, a sensitive network would be one with more than one critical path and/or noncritical activities with very little slack. High sensitivity means focusing on things off the Critical Path. Compares the least amount of "non zero" slack to the overall project duration.

Questions to ask about Activities:

Which activities must be completed immediately before this activity? These activities are called predecessor activities. Which activities must immediately follow this activity? These activities are called successor activities. Which activities can occur while this activity is taking place? This is known as a concurrent or parallel relationship.

The primary inputs for developing a project network plan:

work packages. *Remember, a work package is defined independently of other work packages, has definite start and finish points, requires specific resources, includes technical specifications, and has cost estimates for the package. However, dependency, sequencing, and timing of each of these factors are not included in the work package. A network activity can include one or more work packages.*