关键链项目管理

https://zh./wiki/关键链项目管理

关键链项目管理（英语：Critical Chain Project Management，缩写为CCPM），是由高德拉特博士创造的一种项目规划和管理方法，它主要侧重于项目执行中所需的资源。

目录

  [隐藏] 

• 1起源
• 2详细介绍
• 3方法论
  • 3.1计划
  • 3.2执行
  • 3.3监测
• 4参见

起源[编辑]

详细介绍[编辑]

关键链被用来替代关键路径分析方法。关键链区别于关键路径的主要特征如下：

1. 使用资源依赖
2. 缺乏寻求最佳方案的方法。这意味着一个“足够好”的解决方法已经足够了，因为：
   1. 就目前所知，没有任何分析方法能找到一个绝对的最佳的（比如，总体的最短关键链）。
   2. 估算上的固有的不确定性，远远大于最优和接近最优（即“足够好”的解决方案）之间的差异。
3. 插入缓冲
   • 项目缓冲（Project Buffer，缩写为PB）
   • 输入缓冲（Feeding Buffer，缩写为FB）
   • 资源缓冲（Resource Buffer，缩写为RB）
4. 监测项目的进展和缓冲的使用率，而不是规划个别任务的进展速度。

方法论[编辑]

计划[编辑]

项目计划的建立，和关键路径大致相同。一个落后的任务完成后下一个计划才可能开始。每个任务都输入两个持续时间：一个“最好的猜测”或者50％可能的持续时间，以及一个能高可能地完成任务的“安全”持续时间（也许是90％或95％，依赖于项目组能接收的风险量）。

执行[编辑]

监测[编辑]

参见[编辑]

• 甘特图
• PMBOK
• Prince2
• 计划评审技术（PERT）
• 项目
• 项目管理
• 项目计划
• 工作分解结构
• 关键路径，

https://en./wiki/Critical_chain_project_management

Critical chain project management (CCPM) is a method of planning and managing projects that emphasizes the resources (people, equipment, physical space) required to execute project tasks. It was developed by Eliyahu M. Goldratt. It differs from more traditional methods that derive from critical path and PERT algorithms, which emphasize task order and rigid scheduling. A critical chain project network strives to keep resources levelled, and requires that they be flexible in start times.

Contents

  [hide] 

• 1Origins
• 2Details
  • 2.1Planning
  • 2.2Execution
  • 2.3Monitoring
• 3Underpinnings of CCPM
• 4See also
• 5References
• 6Further reading
• 7External links

Origins[edit source]

This section has been nominated to be checked for its neutrality. Discussion of this nomination can be found on the talk page. (November 2013) (Learn how and when to remove this template message)

Critical chain project management is based on methods and algorithms derived from Theory of Constraints. The idea of CCPM was introduced in 1997 in Eliyahu M. Goldratt's book, Critical Chain. Application of CCPM has been credited with achieving projects 10% to 50% faster and/or cheaper than the traditional methods (i.e., CPM, PERT, Gantt, etc.) developed from 1910 to 1950s.^[1]

According to studies of traditional project management methods by Standish Group and others as of 1998, only 44% of projects typically finish on time. Projects typically complete at 222% of the duration originally planned, 189% of the original budgeted cost, 70% of projects fall short of their planned scope (technical content delivered), and 30% are cancelled before completion^[2] CCPM tries to improve performance relative to these traditional statistics.

Details[edit source]

With traditional project management methods, 30% of lost time and resources are typically consumed by wasteful techniques such as bad multitasking (in particular task switching), student syndrome, Parkinson's law, in-box delays, and lack of prioritization.^[3]

In a project plan, the critical chain is the sequence of both precedence- and resource-dependent tasks that prevents a project from being completed in a shorter time, given finite resources. If resources are always available in unlimited quantities, then a project's critical chain is identical to its Critical path method.

Critical chain is an alternative to critical path analysis. Main features that distinguish critical chain from critical path are:

1. Use of (often implicit) resource dependencies. Implicit means that they are not included in the project network, but must be identified by looking at the resource requirements.
2. Lack of search for an optimum solution—a "good enough" solution is enough because:
   1. As far as is known, there is no analytical method for finding an absolute optimum (i.e., having the overall shortest critical chain).
   2. The inherent uncertainty in estimates is much greater than the difference between the optimum and near-optimum ("good enough" solutions).
3. Identification and insertion of buffers:
   • Project buffer
   • Feeding buffers
   • Resource buffers (companies are usually reluctant to give more resources)
4. Monitoring project progress and health by monitoring the consumption rate of the buffers rather than individual task performance to schedule.

CCPM planning aggregates the large amounts of safety time added to tasks within a project into the buffers—to protect due-date performance and avoid wasting this safety time through bad multitasking, student syndrome, Parkinson's Law, and poorly synchronized integration.

Critical chain project management uses buffer management instead of earned value management to assess the performance of a project. Some project managers feel that the earned value management technique is misleading, because it does not distinguish progress on the project constraint (i.e., on the critical chain) from progress on non-constraints (i.e., on other paths). Event chain methodology can determine a size of project, feeding, and resource buffers.

Planning[edit source]

A project plan or work breakdown structure (WBS) is created in much the same fashion as with critical path. The plan is worked backward from a completion date with each task starting as late as possible.

A duration is assigned to each task. Some software implementations add a second duration: one a "best guess," or 50% probability duration, and a second "safe" duration, which should have higher probability of completion (perhaps 90% or 95%, depending on the amount of risk that the organization can accept). Other software implementations go through the duration estimate of every task and remove a fixed percentage to be aggregated into the buffers.

Resources are assigned to each task, and the plan is resource leveled, using the aggressive durations. The longest sequence of resource-leveled tasks that lead from beginning to end of the project is then identified as the critical chain. The justification for using the 50% estimates is that half of the tasks will finish early and half will finish late, so that the variance over the course of the project should be zero.^{[citation needed]}

Recognizing that tasks are more likely to take more time than less time due to Parkinson's law, Student syndrome, or other reasons, CCPM uses "buffers" to monitor project schedule and financial performance. The "extra" duration of each task on the critical chain—the difference between the "safe" durations and the 50% durations—is gathered in a buffer at the end of the project. In the same way, buffers are gathered at the end of each sequence of tasks that feed into the critical chain. The date at the end of the project buffer is given to external stakeholders as the delivery date. Finally, a baseline is established, which enables financial monitoring of the project.

An alternate duration-estimation methodology uses probability-based quantification of duration using Monte Carlo simulation. In 1999, a researcher^[who?] applied simulation to assess the impact of risks associated with each component of project work breakdown structure on project duration, cost and performance. Using Monte Carlo simulation, the project manager can apply different probabilities for various risk factors that affect a project component. The probability of occurrence can vary from 0% to 100% chance of occurrence. The impact of risk is entered into the simulation model along with the probability of occurrence. The number of iterations of Monte Carlo simulation depend on the tolerance level of error and provide a density graph illustrating the overall probability of risk impact on project outcome.

Execution[edit source]

When the plan is complete and the project is ready to start, the project network is fixed and the buffers' sizes are "locked" (i.e., their planned duration may not be altered during the project), because they are used to monitor project schedule and financial performance.

With no slack in the duration of individual tasks, resources are encouraged to focus on the task at hand to complete it and hand it off to the next person or group. The objective here is to eliminate bad multitasking. This is done by providing priority information to all resources. The literature draws an analogy with a relay race. Each element on the project is encouraged to move as quickly as they can: when they are running their "leg" of the project, they should be focused on completing the assigned task as quickly as possible, with minimization of distractions and multitasking. In some case studies, actual batons are reportedly hung by the desks of people when they are working on critical chain tasks so that others know not to interrupt. The goal, here, is to overcome the tendency to delay work or to do extra work when there seems to be time. The CCPM literature contrasts this with "traditional" project management that monitors task start and completion dates. CCPM encourages people to move as quickly as possible, regardless of dates.

Because task duration has been planned at the 50% probability duration, there is pressure on resources to complete critical chain tasks as quickly as possible, overcoming student's syndrome and Parkinson's Law.

Monitoring[edit source]

According to proponents, monitoring is, in some ways, the greatest advantage of the Critical Chain method. Because individual tasks vary in duration from the 50% estimate, there is no point in trying to force every task to complete "on time;" estimates can never be perfect. Instead, we monitor the buffers created during the planning stage. A fever chart or similar graph can be created and posted to show the consumption of buffer as a function of project completion. If the rate of buffer consumption is low, the project is on target. If the rate of consumption is such that there is likely to be little or no buffer at the end of the project, then corrective actions or recovery plans must be developed to recover the loss. When the buffer consumption rate exceeds some critical value (roughly: the rate where all of the buffer may be expected to be consumed before the end of the project, resulting in late completion), then those alternative plans need to be implemented.

Underpinnings of CCPM[edit source]

This section needs expansion. You can help by adding to it.(April 2010)

History and discussion of the underlying principles behind CCPM.

Critical sequence was originally identified in the 1960s.^{[citation needed]}

See also[edit source]

• Theory of Constraints
• Event chain methodology

References[edit source]

1. Jump up^ "Critical Chain Project Management Improves Project Performance". www.. Retrieved 2017-01-27.
2. Jump up^ "The Standish Group Report Chaos" (PDF). www.. Retrieved 2017-07-20.
3. Jump up^ Harvey Maylor, Project Management

Tzvi Raz, Robert Barnes and Dov Dvir, Project Management Journal, December 2003.

Further reading[edit source]

• Project Management In the Fast Lane, ISBN 1-57444-195-7
• Critical Chain Project Management, ISBN 1-58053-074-5
• Projects in Less Time: A Synopsis of Critical Chain, by Mark Woeppel
• Critical Chain in Practice: Using the Theory of Constraints to Manage Projects & Portfolios, by J.P.Bernard & I.Icord, ISBN 978-2-35422-253-6
• A critical look at critical chain project management, Tzvi Raz, Robert Barnes and Dov Dvir, Project Management Journal, December 2003.
• a critical review of "A Critical Look at Critical Chain", Scott Button, EM 540 Research Paper, March 2011
• "Lean, Agile and Six Sigma IT Management", by Peter Ghavami (2008)
• Critical Chain Project Management Theory and Practice, Roy Stratton, POMS 20th Annual Conference, May 2009

https://ja./wiki/クリティカルチェーン・プロジェクトマネジメント

クリティカルチェーン・プロジェクトマネジメント（Critical Chain Project Management、略称CCPM）は、エリヤフ・ゴールドラットが開発した制約条件の理論に基づき全体最適化の観点から開発されたプロジェクト管理手法。

工期短縮、納期遵守率の向上を目指す。

目次

  [非表示] 

• 1概要
  • 1.1クリティカル・チェーン
  • 1.2プロジェクトマネジメント
• 2参考書籍

概要[編集]

クリティカル・チェーン[編集]

近代的なプロジェクトマネジメント理論はクリティカルパス法やPERT法に端を発するが、これらのマネジメント手法は軍事や建築を対象として生まれたことから、「予算の制約よりも納期が優先される（納期を遵守するために潤沢な予算の追加投入が可能）」「作業員を雇用することが容易」という暗黙の前提があった。このため、人員、設備といったリソースが乏しく、競合を起こす場合の制約条件は考慮されてこなかった。

5つのマイルストーン（10から50）と6つの作業（AからF）がある7か月間のプロジェクトのPERTネットワーク図

プロジェクトにおいて各タスクの実行順序を考えたとき、「作業工程上の従属関係」を考慮するのは伝統的なクリティカルパス法やPERT法と同じであるが、CCPMはこれに加えて「必要リソースが限られているために発生する従属関係」の考慮も行う。

図の例で言うなら、作業Aと作業Bに作業工程上に依存関係、従属関係はなく、並行して作業が可能なように見える。この作業Aと作業Bに、リソースが作業量に対して十分ではなく、作業が集中した場合には、作業を順次行わなければならないという従属関係（例えば、開発要員が総勢10名で、作業Aに必要な要員が6名、作業Bに必要な要員が5名といった場合、または、作業A,作業Bのどちらも開発機器Zを排他的に使用して開発する必要がある場合には、作業Aと作業Bの並行実施はできない。）が発生した場合の作業所要期間はクリティカルパスより長くなる。

このように作業工程の従属関係とリソースの従属関係の両方を考慮に入れて、作業所要期間を決めている最も長い作業の流れのことをクリティカルチェーンと呼ぶ。図の例では、クリティカルパスは作業B→作業C、または作業A→作業D→作業Fの7ヶ月であるが、作業A,Bのリソースに従属関係があり並行実施ができない場合、作業A→作業B（あるいは作業B→作業A）→作業D→作業Fの11ヶ月がクリティカルチェーンとなる。

リソースが十分に存在し、各作業での競合が発生しない場合には、クリティカルチェーンとクリティカルパスは同じになる。

なお、PMBOK第3版以降のプロジェクトスケジューリングでは必要リソースに配慮するよう前提が変わったため、この前提にもとづくのならば、クリティカルチェーンとクリティカルパスは同義語になったとも言える。

プロジェクトマネジメント[編集]

開発要員の人間心理や行動特性、および社会的・組織的問題も考慮して、工期短縮、納期遵守率を目的にプロジェクト管理を行う実践的手法である。

従来のプロジェクト管理では、進捗の妨げとなる不確定要素を考慮し意識的にせよ無意識的にせよ余裕（バッファ）をもたせた作業時間を確保しようとする。ゴールドラットは、各タスクにおいて各作業者は作業所要期間見積もりを約2倍のバッファをもたせて確保しようとすると指摘した。

このような自己申告による余裕ある日程計画においては、各作業者は学生症候群（英語版）を引き起こして作業着手を先延ばししたり、早期に完了してもパーキンソンの法則にみられるように予定の計画終了日まで完了報告を上げないといった問題が起こり、結局は余裕ある日程にも関わらず遅延が発生すると、ゴールドラットは指摘する。

こういった事態を改善するために、ゴールドラットはプロジェクトバッファ、合流バッファ、リソースバッファという概念を導入した。

プロジェクトバッファ

バッファを各作業工程（タスク）毎には管理せず、プロジェクト全体で管理するもの。ネットワーク図の上ではクリティカルパスの後ろに置く。

合流バッファ

クリティカルパス以外のタスクで、クリティカルパスに合流するタスクの完了時期に持たせる。

リソースバッファ

同じリソースを使うタスク同士が、前のタスクの遅れにより後のタスクが遅れることがないように配置する。

CCPMにおいて、マネジメントとは各タスクの進捗度合を監視、管理するのではなく、上述した各バッファの消費量、消費速度を監視、管理することになる。

公表された当初は、ソフトウェア開発などには不向きという意見もあったが、近年は大きな成果を示す事例などが報告されている。