Version 17 (modified by Chris Nelson, 9 years ago) (diff)

Fix a typo

Trac is strong in basic, individual and small-team task management but lacks features for heavy-duty project management a la Microsoft Project, Project Manager Workbench, etc. This page discusses those missing features and how they can best be realized.

Requirements and Definitions

Project management support software should help us answer a few basic questions:

  • When will my project be done?
  • How are my resources being utilized?
  • How will a change (e.g., in scope or constraints) affect project completion or resource utilization?

To answer these questions, it must know about:

  • Tasks to be done
  • Dependencies between tasks
  • Resources available to do tasks
  • Assignment of resources to tasks
  • Deadlines for task or project completion

Task Properties

Answering the questions listed above requires recording certain properties of a task.

  • Duration - The amount of work needed to complete the task. This is not, necessarily, the time it will take to complete the task. The task may be unassigned (and will take forever to complete) or has a resource assigned only part-time (so it will take longer to complete than the amount of work indicates).
  • Assigned resource - The individual who will work on this task.
  • % Effort - The amount of the resource's time that will be spent on this task. If the resource is working on a 2-day task 50% of the time, we expect it to take 4 days.
  • % Complete - The amount of the task that has been done already.
  • Dependencies - Other tasks that affect when this task can be started or finished.


Task dependencies can be quite complex. Project management generally involves four types of dependencies between tasks or activities:

Finish-to-Start (FS)
Task B cannot begin until task A is complete. This is the most common. When building a house, the walls cannot be put up until the foundation is complete.
Start-to-Start (SS)
Task B cannot begin until after task A begins (though they may end independently). When building a house, interior painting cannot begin until the dry wall is started. (Each room can be painted as soon as its dry wall is up.)
Finish-to-Finish (FF)
Task B cannot end until task A ends (though they may begin independently). When building a house, inspections cannot be completed until construction has completed (though parts may be inspected before the whole job is done).
Start-to-Finish (SF)
Task B cannot end until Task A begins. When building a house, the builder may begin getting interim payments during construction but payment will not be completed until the owner can start moving in.

In addition, managing the complexity of a large project requires breaking large tasks into smaller ones (or viewing groups of small tasks as larger aggregates). For example, interior painting might be broken down into paint the living room, paint the dining room, etc.

While useful, the FF and SF dependencies are somewhat more esoteric than the others and implementation may be deferred.

NOTE: The relationships are directional and inverting them is not straightforward. If A has a FS dependency on B, it is not true that B has an SF dependency on A.

Gantt Charts

The basic answer to "When will my project be done?" is generally provided by a Gantt chart which shows tasks, their dependencies, their duration (scaled by resource availability), and milestones. As discussed in two threads on the Trac Users mailing list, a Gantt chart is a fundamental requirement for project management.

Trac has three Gantt chart plugins:

seems complex and stale.
is a very simple Gantt chart implemented in a formatted text region. It is manually edited, not data-driven.
has potential but has some funky fields (e.g., Due to Assign) that don't seem to be appropriate to what we want to do with a Gantt chart.

Gantt Chart Components

In its most basic form, a Gantt chart shows:

Self-contained units of work
Relationships between tasks that constrain when they can be done
Dates by which one or more tasks must be completed

It may also show resource assignments and progress in tasks. It often includes a "today" line to show where a project stands. (If the project is on schedule, all tasks to the left of today are complete and any task that spans today has a progress bar to the right of today.)

A Gantt chart may also show slack time for tasks, how much they can slip before affecting the overall schedule. It often also highlights the critical path, the set of tasks which determine the overall length of the project and which delay the project completion unit-for-unit as they are delayed or extended.

Component Data

Each Gantt chart component or feature requires data to support it. For Trac-based project management, this data is often in addition to the core ticket data.

In general, we might expect to have multiple resources assigned to a task but if we use a Trac ticket as the basis for a task, we have only a single resource, the ticket owner.

Core Fields

Core ticket fields include relevant to project management include:

  • owner (who is working on it)
  • milestone (what milestone this ticket is part of)
  • status (new, assigned, ..., closed)
  • summary (short description)

Core milestone fields relevant to project management include:

  • name
  • due (date and time)
  • completed (treated as a Boolean: open or closed)

Additional Data

For project management, we must have the following additional information about a task/ticket:

  • estimate (expected work required to complete task)
  • percent complete
  • dependencies
  • percent effort

NOTE: While Gantt charts typically show percent complete, this can be computed from time remaining vs. total estimate or time worked vs. total estimate. We will not, necessarily, store percent complete. It is intuitive for display and analysis but difficult for data entry.

Related Work

MasterTicketsPlugin supports FS dependency (but calls it blocks and blocked by).

The SubTickets page talks about adding composition type dependency. Can this be done in a plugin like MasterTickets or must it be in the core?

TimingAndEstimationPlugin and TracHoursPlugin add estimated and actual hours fields to tickets. There is some disagreement about whether the estimate is the remaining time (so total estimated time is actual + estimate) or total time (so remaining time is estimate - actual). A Gantt chart typically wants estimate and percent complete. It is possible to extract this from either recording convention and we should likely allow either convention via a configurable interface.

There is a Google Gadget Gantt chart which might be leveraged for the visualizations once the data is made available (e.g. using [http: TracGViz plugin]). That widget is developed and maintained by a company (i.e. ViewPath). Besides users need access to the internet and their projects environments have to be available too so that the iGoogle container be able to retrieve the data to display in the chart. All this means that local deployments (intranets, ...) are not possible.


A Gantt plugin for Trac should analyze ticket dependencies and produce an interactive, explorable Gantt chart showing task progress and project status.

By "project", I mean a set of related milestones. Perhaps a software project has a Design Phase, an Alpha Release, a Beta Release, and a General Release. Each phase would have a milestone with a target date and tickets to complete the work for that phase. There must be a way to specify which milestones to include either listing explicitly or by giving a pattern or substring filter.

What do we need in the back end ?

The chart should be able to show all tickets (though that may be a very complex chart) or alternately all those tickets matched by a (query | report) or any other ticket group provider.

To effectively display project progress, tickets must have estimated and actual times as in the TimingAndEstimation plugin.

It is also desirable to have loop detection to error-proof the tool used to create dependencies.

It would be nice to be able to choose an As Late As Possible or As Soon As Possible algorithm for laying out tasks.

What do we need in the user interface ?

A "chart these" button on a report page would be very nice.

Tasks in the chart should be links to the tickets they represent (preferentially opened in a separate tab or window).

Milestones should be displayed in the chart as well.

The chart should support interactively "folding" groups of tasks to hide detail.

Zooming in order to see the WBS in more detail.

Panning or scrolling in order to display the schedule at a different time.

Each task's bar in the chart should show actual hours.

The chart should have a Today line.

The chart (or an accompanying report or tool) should aid in resource leveling by (at least) showing overcommitted resources.

Visual indications about delays, task completion and other significant events.

It would be nice to be able to create task dependencies graphically using the Gantt chart as a GUI or to change a milestone date by dragging it along the chart.

Design guidelines

In order to agree about how to implement this functionality, the very first step should be to describe the possible architectures (i.e., how the different components are going to interact with each other since the moment the request is sent by the client until the Gantt chart is rendered by the browser) that will be considered.


In order to add flexibility to the final solution, the MVC pattern should be considered during its development. Hence the following components need to be implemented in order to add Gantt charts to Trac.

The Model

It provides the data in the Gantt chart and is not just a single element but a set of components like the following :

  • The ticket models, which provide data about the issues found in the project environment
  • Trac query mechanism which provides a way to select (filter) the tickets being shown.
  • Other plugins used to track ticket dependencies
  • Other plugins used to track task/subtask relationships
  • Other plugins used to estimate the time needed to finish the given tasks
  • Maybe one (a few) component(s) whose role is to provide the functionality specific to Gantt charts, thus acting as a central access point and a mediator so as to put all the other components together.

The View

It should be a JavaScript component (is this possible ?) responsible for rendering the data provided by the model. Besides it might support other dynamic features

The Controller

¿What do we need this for?


The aforementioned separation should allow the replacement of any of the components involved. Hence the following modifications should be made easily (the list being intentionally incomplete) :

  • Replace the JS-based view by another made with Flash.
  • Use a custom, or specific estimation strategy.


There seems to be a consensus that grandiose project management features for Trac should be implemented with a combination of plugins which provide useful functionality on their own. The following plan assumes that approach.

  1. Fork MasterTickets as TicketDep (or something) and add composed of/part of dependencies and means to create them. Plan for but do not yet implement starts with and ends with dependencies.
  2. Specify the interfaces necessary for a scheduling plugin to use dependencies, estimates, and time worked to determine project schedule.
    • Consider adding a percentage available when scheduling resources.
  3. Specify the interfaces necessary for a Gantt chart to get data from tickets.
    • Each task must have a name, duration, percent complete, and start or end. (The start or end comes from schedule calculations, not direct ticket data.)
    • Access to dependencies between tickets is also needed so as to render the chart.
  4. Implement those interfaces on top of TimingAndEstimationPlugin.


The bulk of this page was prepared by Chris Nelson who makes no claim to be certified project planner or anything of the sort. It is based on his understanding of project management after 25 years of software development. Other developers have also offered some hints and useful comments (according to their experience) in order to enhance this page, and get a better understanding of the features and requirements needed.


  • Olemis Lang

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