Marginalia

• Sequencing establishes the logical order of the tasks. Therefore one can also say that sequencing at least expatiates the intrinsic domain specific order of the tasks.

(3.2) Activity Sequencing

(3.2.1) Process Input

... generated by predecessor processes

(3.2.2) Process Definition

Activity Sequencing is the process for "[...] identifying and documenting dependencies among schedule activities" (comp. PMBOK3, p. 123), also known as "logical relationships" (comp. PMBOK3, p. 130): Having the list of (all) activities which together constitute all or some of the work packages, one answers the question, which tasks have to be started and/or finished before or after other tasks (without reflecting the question, who have to do the tasks or how long they will have to work).

The subject Time operates on the base of other time concerning concepts

(3.2.3) Tools and Techniques

PMBOK Mentioned Methods

  • Precedence Diagramming Method (PDM) (also known as Activitiy On Node (AON) technique) is that method for documenting an activity sequence, by which each activity is represented as a node and each node is connected to its successors by an arrow. (mathematically expressed: an acyclic directed graph, but not necessarily a tree: Nodes may have more than one father, but no daughter can indirectly become a father of its own father). Because in this case the nodes represents activities with a durance, one can determine the sucessor- or predecessor-releation by subtypes:
    • Finish-to-Start :- the predecessor has to be finished before successor can start
    • Finish-to-Finish :- the predecessor has to be finished before successor can be finished
    • Start-to-Start :- the predecessor has to be start before successor can be started
    • Start-to-Finish :- the predecessor has to be start before successor can be finished
  • Arrow Diagramming Method (ADM) (also known as Activitiy On Arrow (AOA) technique) is that method for documenting an activity sequence, by which each activity is represented as an an arrow and the nodes are the states (of deliverables) which have been reached (generated) by the activities. Because of the structure of this method there exist only one kind of relationship (finish-to-start). And dependencies between states - which don't refer to activities - must be expressed as dummy-activities (no work content, zero durance)
  • Schedule Network Templates are often given as domain specific template
  • Dependency Determination tries to clear the relationship between activies:
    • Mandatory dependencies "[...] are inherent in the nature of the work being done".
    • Discretionary dependencies are dependencies evoked by tradition or best practice and so on and are also known as those, which base on "soft logic" or "prefrential logic". (But of course best practice might be inadequate for the concrete single case.)
    • External dependencies are dependencies on states or products and so on which must be reached, given etc. but which don't are generated by the project itself. Therefore: external dependencies often should become part of the risklist
  • Applying leads and lags:
    • "A lead allows an accelaration of the successor activity": only one part of the predecessor must really be ready before the successor can be started. This will be expressed as finish-to-start relation with x units lead time.
    • "A lag directs a delay of the successor activity": if there must be a pause between predecessor and sucessor, than one has to generate a finish-to-start-relation with x units lag time.

(comp. PMBOK3, pp. 132ff)

Open Source Tools

  • Planner offers a project schedule file containing the successor and predecessor relations of the activities.

(3.2.4) Process Output

  • Project Schedule Network Diagrams are the generated digrams, either activity on node diagramms (AON), generated by the predecence diagramming method (PDM), or activity on arrow diagrams (AOA), generated by arrow diagramming methods (ADM).
  • Updates of the Activity List can be evoked during the activity sequencing.
  • Updates of the Activity Attributes will surely be evoked during the activity sequencing because predecessor / successor relationships, leads and lags are activity attributes.
  • Requested Changes might be evoked because by Activity Sequencing one can find new necessary activities, work packages and so on

(3.2.5) Output Using Successor Processes

Successors using the initially generated output as own input(1):

Processes using the updates as input(2):

  1. For details see FAQ::Q001:1
  2. For details see FAQ::Q001:2