Applied Signposting model

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The ASM (Applied Signposting Model) is a process modelling approach developed to model and simulate engineering design processes and other project workflows that can include iteration. It is based on a simple graphical notation reminiscent of a flowchart, designed to be easy to read for large models and by unfamiliar users. It combines this graphical simplicity with the ability to create highly-configurable workflow simulation models. Simulation experiments can be designed to try out different process configurations in a 'virtual environment' (eg. using Design of Experiments methodology)

Why use the ASM? Many process modelling tools are based on standard notations such as UML and BPMN. Those notations have many benefits including their comprehensive, standards-compliant and implementation-independent nature. However, we have found that they are often too 'verbose' and heavyweight, leading to models which are physically large and difficult to read. This can be problematic when modelling large, complex, semi-structured processes comprising 100s or 1000s of activities.

We have found that complex notations are not always the best option for developing large process models in an iterative, collaborative setting, where domain experts must be quickly brought on-board and aligned with the modelling notation and with the content of a particular model. We have found the simple, relatively 'transparent' notation of the ASM approach useful to focus attention on the process, rather than the modelling. This is supported in CAM by various functionalities to help with creating and managing large, hierarchical models.

Strengths and weaknesses: The main strength of the approach is its simple graphical notation which makes it easy to comprehend complex processes, even for unfamiliar users. The approach is well-suited to model and simulate 'semi-structured' processes where the modeller wishes to represent particular behaviours and process scenarios. The simulation logic can handle complex, intertwined processes containing rework and iteration. However, the graphical notation is not ideal for very densely interconnected processes, which can often be better modelled using a Dependency Structure Matrix (DSM). The simulation algorithm does not currently support overlapping and has only rudimentary support for handling resource limitations. These shortcomings may be addressed in future releases.

An example ASM model is shown in the screenshot below (click any figure on this site to enlarge it). Keep reading for more information..

 

The ASM notation comprises 4 types of node, some of which are visible in the screenshot above:

  1. Deliverables (blue ellipses) - represent packages of information or materials that are considered, created or modified by tasks. See also the information on ASM info/material items.
  2. Simple tasks (yellow rectangles) - represent tasks which take account of inputs to create outputs. All the outputs of a simple task are created (or updated) at the same time, when the task is complete.
  3. Compound tasks (red rectangles) - Similar to a simple task, but can have one or more output 'scenarios'. Each scenario represents a different 'forward branch' and contain one or more deliverables.
  4. Iteration constructs (Green diamonds) - Similar to a compound task, but represent the possibility of generating a 'backward branch' (iteration).

These four types of node (shapes on the diagram) can be connected using two types of dependency (arrow):

  1. Flow dependencies (solid lines) - the dependency contributes to the timing of the downstream task (eg. the upstream deliverable must be available to start the task)
  2. Data dependencies (dashed lines) - the dependency indicates that the upstream information is used while executing the downstream task, but doesn't determine when the task can be attempted.

Other types of item are (usually) not shown directly on the diagram:

  1. Resources - represent the individuals, teams or other resources that are needed to perform tasks. These can be created and browsed using the Resources tree in the EXPLORER tab of the left-hand side of the CAM window. Once created, they may be assigned to tasks on the ASM flow diagram. Resource limitations constrain the number of tasks that can be executed concurrently during an ASM simulation.
  2. Info/material items - represent the information, material etc. that is modified by tasks and contained in deliverables. Associated with deliverables on the ASM flow diagram.
  3. Variables - used in simulation models to represent KPIs etc. and their interrelationships with tasks in the process. May be global, or associated with specific tasks and info/material items.

In the screenshot above, some Info/Material items have been placed as shortcuts on the diagram to depict an information hierarchy. These appear as circles at the top of the screen.

How to build an ASM process/simulation model in CAM

For getting started, we recommend the task oriented documentation on the Use cases section of this website. More comprehensive feature-oriented information can be found here:

  • Modelling a process: See the information on the ASM Modelling page.
  • Simulating a process: See the information on the ASM Simulation page.

More information 

  • The "first generation" ASM was described in this paper and this thesis. The approach has since been refined to create the version now implemented in CAM. Recent applications are discussed in these publications:
  1. Modelling the evolution of uncertainty levels during design. WYNN, D.C., GREBICI, K. and CLARKSON, P.J. (2011) International Journal on Interactive Design and Manufacturing, Vol. 5, No. 3
  2. Redesigning the design process through interactive simulation: A case study of life-cycle engineering in jet engine conceptual design. KERLEY W.P., WYNN, D.C., ECKERT, C.M. and CLARKSON, P.J. (2011) International Journal of Services and Operations Management, Vol. 14, No. 1
  3.  Simulating intertwined design processes that have similar structures: a case study of a small company that creates made-to-order fashion products. WYNN, D.C.,  ECKERT, C.M., CLARKSON, P.J. (2011) International Journal of Product Development, Vol. 14, Nos. 1-4