Activity planning
Activity planning turns a milestone plan into tasks: who does which piece of work, in what order, and what each task must wait for. The inventors of the critical-path method kept order and time apart: “We defined planning as the act of stating what activities must occur in a project and in what order these activities must take place.” Dates come afterwards [1].
1. Who commits to a task: pull or push
In Scrum the team pulls. The development team decides what it can deliver, and the ScrumMaster “cannot decide on behalf of the development team what commitment to make”. Rubin warns that “assigning tasks to individuals might be harmful if doing so reduces team ownership of the tasks” [2]. Capacity is measured first. For example, a team averaging 40 points plans about 20 for a sprint full of holidays, and checks skills as well as hours.
In a plan-driven project the manager pushes: “Every task that is scheduled should be assigned to a specific team member.” Its companion is effort validation: three engineers cannot carry seven parallel half-day tasks [3].
Under pull the team holds the autonomy and answers to itself for the sprint. Under push the manager holds the commitment and answers for the whole schedule.
2. When: one wave at a time
Both styles plan the detail late. Scrum fixes the work for a sprint “at the last responsible moment—the sprint planning for that sprint” [2]. In a plan-driven project, “The activity planning for achieving a specific milestone may wait until close to the starting of the work on this milestone”, because planning early means “the planner chooses early solutions, not optimal solutions” [4]. That is rolling wave planning [5].
3. The activity network
An activity network records which task waits for which. The 1959 method drew tasks as arrows and needed dummy activities; today’s activity-on-node form puts tasks in boxes and needs none [6]. It can also carry lags and percent-complete conditions [7].
Kelley and Walker 1959, Fig. 1.
People are left out on purpose: “Considerations of available manpower and equipment are conspicuous by their absence” [1]. What the network gives instead, in Brooks’s words: “Such a network shows who waits for what.” [8]
4. Example: four dependency types in Quill
Quill is a fictional word processor going live at a publishing house. Each dependency has a reason:
| Type | Quill example | Reason |
|---|---|---|
| Finish-to-start (FS) | Tuning for 500-page documents starts when the new PDF engine is in | Technical: nothing to tune before |
| Start-to-start (SS), 1-week lag | Translating the help centre starts a week after writing it starts | Management: accept rework to save time |
| Finish-to-finish (FF) | The citation-style guide cannot finish before the last style does | The guide covers every style |
| Start-to-finish (SF) | The old word-processor licences end only after Quill goes live | The legacy system stops once the new one runs |
The reason decides whether a link can change: management dependencies “can be reversed, while technical dependencies cannot”. Wysocki calls FS “the simplest and most risk-averse of the four types”, so start with FS everywhere and relax a link to SS or FF only when the date demands it [6]. Relaxing buys time with the risk of rework.
5. When to use it, and where it misleads
Use a network when several people’s work interlocks and the order is not obvious. Skip it inside a sprint, where the team sequences its own tasks.
Expect the first draft to be wrong: “The first chart is always terrible.” Drawing it is still the most valuable part, because it forces dependencies into the open [8]. And a network gives no dates by itself. The critical path computes them, PERT shows why they come out early, resource planning fits them to people, and a Gantt chart displays them.
How solid is this?
- Where it comes from. The inventors’ 1959 report, practitioner and software engineering textbooks, a defence-acquisition guide and a Scrum practitioner book. No study compares pull with push.
- What is ours. Pull and push are the lecture’s words; Rubin and Pressman supply the mechanisms without using them. The Quill dependencies are constructed for teaching.
Acknowledgments
This page adapts material from lectures by Eduardo Miranda [9] on software project management.
References
- J. E. Kelley Jr. and M. R. Walker,“Critical-Path Planning and Scheduling,” in Papers Presented at the December 1–3, 1959, Eastern Joint IRE-AIEE-ACM Computer Conference, ACM, 1959, pp. 160–173. doi: 10.1145/1460299.1460318.
- K. S. Rubin,Essential Scrum: A Practical Guide to the Most Popular Agile Process. in Addison-Wesley Signature Series (Cohn). Addison-Wesley Professional, 2012. [Online]. Available: https://innolution.com/essential-scrum
- R. S. Pressman,Software Engineering: A Practitioner’s Approach, 7th ed. McGraw-Hill, 2010.
- E. S. Andersen,“Warning: activity planning is hazardous to your project’s health!,” International Journal of Project Management, vol. 14, no. 2, pp. 89–94, Apr. 1996, doi: 10.1016/0263-7863(95)00056-9.
- G. D. Githens,“Rolling Wave Project Planning,” in Proceedings of the 29th Annual Project Management Institute 1998 Seminars & Symposium, Project Management Institute, Oct. 1998. [Online]. Available: https://www.wcu.edu/pmi/1998/NP02.PDF
- R. K. Wysocki and R. McGary,Effective Project Management: Traditional, Adaptive, Extreme, 3rd ed. Wiley Publishing, 2003.
- F. P. Brooks,The mythical man-month (anniversary ed.). Addison-Wesley Longman Publishing Co., Inc., 1995.
- E. Miranda,“Managing Software Development.” 2014.
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