● The cost, risk, and communications decisions from the project management plan are used to develop the schedule.
● The project charter defines the summary milestone schedule and project approval requirements that will influence the management of the project schedule.
The enterprise environmental factors that influence the Plan Schedule Management process include:
- Organizational culture and structure
- Resource availability and skills
- Project management software (e.g. MS Project, this depend on different company,so why it is enterprise environmental factors.)
- Published commercial information
- Organizational work authorization systems
Schedule Management Plan
May be formal or informal, highly detailed or broadly framed. Includes:
- Project schedule model development methodology and tools to be used.
- Level of accuracy 規定活動持續時間估算的可接受範圍
- Units of measure staff hours, staff days, or weeks for time measures, or meters, liters, tons, kilometers.
- Organizational procedures links The WBS provides the framework for the schedule management plan, allowing for consistency with the estimates and resulting schedules.
- Project schedule model maintenance The process used to update the status and record progress of the project in the schedule model during the execution of the project is defined.
- Control thresholds Variance thresholds 用於監督進度績效，當出現重大偏差，就有可能要採取某種措施。通常用基准計劃（baseline plan）中的參數的某個百分數來表示。
- Rules of performance measurement 規定用於績效測量的掙值管理（Earned value management (EVM)）規則或其他測量規則
For example, the schedule management plan may specify: - Rules for establishing percent complete - 制定完成百分比的規則
- Control accounts at which management of progress and schedule will be measured - 制定完成百分比的計算項目
- Earned value measurement techniques
- Schedule performance measurements such as schedule variance (SV) and schedule performance index (SPI) compare to the original schedule baseline
- Reporting formats - 各種進度報告的格式和編制頻率
- Process descriptions - 進度管理過程的描述
6.2 Define Activities
● The Inputs of Define Activities should includes Scope Baseline.
Described in Section 5.4.3.1. The project WBS, deliverables, constraints, and assumptions documented in the scope baseline are considered explicitly while defining activities. WBS is modeling by 100% rules, so it prevent to missing work item.
● Activity Attributes have durations, resources and costs associated. During the initial stages of the project, they include the activity identifier (ID), WBS ID, and activity label or name, and when completed, may include activity codes, activity description, predecessor activities, successor activities, logical relationships, leads and lags, resource requirements, imposed dates, constraints, and assumptions.
● Activity Identifier vs Activity Code
Activity Identifier is a unique code we assign to each of the project activities to differentiate them from each other as well as for referencing purposes. Activity Codes are not unique , i.e., same code can be given to multiple activities. One reason behind this concept is to group similar activities together so that they can be filtered-out of the project plan for further analysis.
● Activity attributes can be used to identify the person responsible for executing the work, geographic area, or place where the work has to be performed.
● LOE = level of effort
● Activity attributes are used for schedule development and for selecting, ordering, and sorting the planned schedule activities in various ways within reports.
● Milestones are similar to regular schedule activities, with the same structure and attributes, but they have zero duration because milestones represent a moment in time.
6.3 Sequence Activities
Precedence diagramming Method
- Finish-to-start (FS). A logical relationship in which a successor activity cannot start until a predecessor activity has finished. Example: The awards ceremony (successor) cannot start until the race (predecessor) has finished.
- Finish-to-finish (FF). A logical relationship in which a successor activity cannot finish until a predecessor activity has finished. Example: Writing a document (predecessor) is required to finish before editing the document (successor) can finish.
- Start-to-start (SS).A logical relationship in which a successor activity cannot start until a predecessor activity has started. Example: Level concrete (successor) cannot begin until pour foundation (predecessor) begins.
- Start-to-finish (SF).A logical relationship in which a successor activity cannot finish until a predecessor activity has started. Example: The first security guard shift (successor) cannot finish until the second security guard shift (predecessor) starts.
Dependency Determination
- Mandatory dependencies - e.g. A unit test cannot be run until the test case is write.
- Discretionary dependencies
- External dependenciesWhen is the programmer start their work dependent on the delivery of hardware from IBM.
- Internal dependencies
● Lead - in a finish-to-start dependency with a ten-day lead, the successor activity can start ten days before the predecessor activity has finished.
● Lag - in a finish-to-start dependency with a ten-day lag, the successor activity cannot start ten days after the predecessor activity has finished.
6.5 Estimate Activity Durations
● Analogous estimating is a technique for estimating the duration or cost of an activity or a project using historical data from a similar activity or project.
● Analogous estimating is generally less costly and less time consuming than other techniques, but it is also less accurate.
● Parametric Estimating uses a statistical relationship between historical data and other variables. Activity durations can be quantitatively determined by multiplying the quantity of work to be performed by labor hours per unit of work.
For example, activity duration on a design project is estimated by the number of drawings multiplied by the number of labor hours per drawing, or on a cable installation, the meters of cable multiplied by the number of labor hours per meter. For example, if the assigned resource is capable of installing 25 meters of cable per hour, the duration required to install 1,000 meters is 40 hours. (1,000 meters divided by 25 meters per hour).
● Three-Point Estimating (三點估算法)
- Most likely(tM)最可能值
- Optimistic(tO)樂觀值
- Pessimistic(tP)悲觀值
- Triangular distribution. tE = (tO + tM + tP)/ 3 (or P+M+O/3 easy to memorize)
- Beta distribution(from the traditional PERT technique). tE = (tO + 4tM + tP)/ 6 = (O+4M+P)/6
- Standard Deviation (標準偏差) - (Pessimistic - Optimistic) / 6
Example:
Duration of an activity has the following estimates:
Optimistic – 3 days;
Most Likely – 5 days;
Pessimistic – 13 days.
The time estimate for that activity based on the triangular distribution is 7 days. (13+5+3/3)
Reserve Analysis
Duration estimates may include contingency reserves (可能性的保留), sometimes referred to as time reserves or buffers. Contingency reserves are associated with the "known-unknowns," which may be estimated to account for this unknown amount of rework.
Activity duration Estimates
Activity duration estimates are quantitative assessments of the likely number of time periods that are required to complete an activity.
Duration estimates do not include any lags.
Activity duration estimates may include some indication of the range of possible results.
For example:
- 2 weeks ± 2 days, which indicates that the activity will take at least eight days and not more than twelve (assuming a five-day workweek); and
- 15 % probability of exceeding three weeks, which indicates a high probability—85 %—that the activity will take three weeks or less.
6.6 Develop Schedule
Schedule network Analysis
● Critical Path Method (CPM, 要徑法)
CPM是用來評估專案最少所需要的時候，以及各路徑的彈性時候。
● The sequence of A-C-D is the critical path. The critical path is the sequence of activities that represents the longest path through a project.
● Critical path is zero total float.
● Free Float (浮時)- The amount of time that a schedule activity can be delayed without delaying the early start date of any successor or violating a schedule constraint.
● Free Float計算方法 : 下一個活動的ES - 這個活動EF - 1，For example the free float for Activity B = 16 - 10 -1 = 5 days.
If start from day "0", there is no need to subtract "1."
● Total Float (Also call Float or Slack),計算方法 : LS-ES or LF-EF. Precedence Diagramming Method
Difference between Total Float and Free Float
● Total float is the amount of time an activity can be delayed without impacting the project schedule.
● Free float is the amount of time an activity can be delayed without impacting the early start date of any of its successors.
e.g. Critical path A-E-F-H : 40 days
Branch A-B-D-H: 36 days,
then Float for each of the activities A, B, D, H is 40-36 = 4 days
i. e. you can use this 4 days spare time and put up that much delay on any one of the A/B/D/H or any combination of activities - not to exceed 4 days otherwise you will be slipping from the schedule completion
Critical Chain Method (CCM)
● CPM is Time Critical, but CCM is Resource Critical.
Resource Leveling (資源撫平)
What is the difference between Resource Levelling and Critical Chain method?
Both are schedule network analysis methods.
When you are preparing a schedule for the project you will try to get the critical path for the project. After taking into account dependencies / constraints you would have prepared the schedule. Now you will have to check the resource situation. If you dont have enough resources then you will have to alter the schedule. This resource constrained critical path is called critical chain.
Now resource levelling does not always result in extension of critical path. In resource levelling you are checking if all resources are loaded around 100%. If someone is above 100%, then you will have to either extend the schedule or move some tasks to other resources.
Another important thing that you do in critical chain is add buffers to manage uncertainties. Since you are resource constrained , chances are there will be some unplanned leaves or unavailabilities of resource. In order to account for that feeder buffers and project buffers are added in critical chain method.
Resource Leveling vs Resource Smoothing Resource Smoothing is subset of Resource Leveling. Leveling allows for changes to the critical path, but Smoothing does not allow.
● What-If Scenario Analysis - 試著模擬變動某個活動的工期，資料，然後要徑、完工日、強制日期(imposed date, 某活動一定要在特定日期)是否變動。
Schedule Compression
● Schedule compression techniques are used to shorten the schedule duration without reducing the project scope, in order to meet schedule constraints, imposed dates, or other schedule objectives.
- Crashing - shorten the schedule duration for the least incremental cost by adding resources, e.g. approving overtime. Crashing works only for activities on the critical path, may result in increased risk and/or cost
- Fast Tracking - activities or phases normally done in sequence are performed in parallel. Fast tracking may result in rework and increased risk. Fast tracking only works if activities can be overlapped to shorten the project duration.
6.6 Develop Schedule: outputs
● Schedule Baseline is the approved version of a schedule model that can be changed only through formal change control procedures and is used as a basis for comparison to actual results.
● Project Schedule, a schedule model are schedule presentations.Which are classified as presentations:
- Bar charts also known as Gantt charts includes activity durations, start and finish dates.
- Milestone charts similar to bar charts, but only identify the scheduled start or completion of major deliverables.
- Project schedule network diagrams -
showing activities and relationships without a time scale = pure logic diagram or presented in a time-scaled = logic bar chart
沒有留言:
發佈留言