W3_GGS_OmniClass WBS Table Selection Using Additive Weighting Technique

Problem Statement

Project objectives and the scope of work form the basic of the a project. To achieve the project objectives, the first step is to start with the scope of work definition or technical statement of the project. The second step will be to develop scope of work into a work breakdown structure (WBS). The WBS logically displays subdivision of the complete project into smaller, more manageable, pieces of works. Then, the third step is to prepare WBS dictionary to define the work included within each WBS element.

There are some WBS dictionaries which have been formed and developed to help the Project Manager to build their project’s WBS. One of them is OmniClass Construction Classification System. OmniClass consists of 15 tables, each of which represents a different facet of construction information. As the OmniClass covers many areas, not always all the tables are useful and relevant to a project, in this case, to the water supply project. Project Manager then, shall determine which one(s) of the tables that will be most applicable for this project?

Feasible Alternative

To choose 2 or 3 most applicable tables from the 15 tables, the most appropriate technique will be the multi attributes approach. Compensatory models, the additive weighting technique has been chosen to help performing the comparison and selection. In all compensatory models, which involve a single dimension, the values of all attributes must be converted to a common measureable scale. By using determined criteria related to the water supply project, the additive weighting technique will rank the 15 tables (rank 1-15), shows high to low applicability and relevance to the project.  

Compensatory Models – Additive Weighting Technique Approach

There are 4 criteria related to water supply project that have been determined for the OmniClass tables selection:

  1. Tables applicability/uses for construction type of project (low to high)
  2. Recommended Table Users – related to project member (design and construction) (1-6, 6 being preferable)   
  3. WBS Level detail completeness (1-4, 4 being preferable)  
  4. WBS Deliverables related to Construction of Water Supply and Water Treatment Project (1-5, 5 being highest relationship)

These are used as basic criteria to compare each OmniClass tables. The result is shown in the following table 1. 

Table1 OmniClass Tables Comparison Based on Selection Criteria

From the 4 selection criteria, criteria no 4 has the highest ordinal ranking, then, in sequence followed by criteria no 3, no. 1 and no.2.  This result is used to determine the attribute weight as show on table 2. 


Table 2 OmniClass Tables Selection – Attribute Weight

The attributes values on table 1 above  has to be converted in to non dimensional form. The procedure for converting the original data on table 1 for a particular attribute to its dimensionless rating is:

 Rating  =         Outcome being made dimensionless – Worst Outcome 

                                     Best Outcome – Worst Outcome

The non dimension (dimensionless) values of the attributes are shown on table 3 

Table 3 OmniClass Tables Selection – Dimensionless Value

Finally, for each OmniClass table, the normalized weight of the attribute (table 2) is multiplied the non dimensional attribute value (table 3) to obtain a weighted score for the attribute. These weighted score are then summed to arrive at an overall score for each OmniClass table. The result is shown on table 4. 

Table 4  OmniClass Tables Selection – Weighted Score

Result and Conclusion

Based on calculation and table comparison above, the most applicable and relevant WBS from OmniClass for the water supply project are:

  1. Table 22 – Work Results
  2. Table 23 – Products
  3. Table 21 – Elements

Next Steps

The next step will be to build up WBS for the water supply project using the three selected OmniClass WBS above, to prove whether the conclusion above is correct and appropriate, and use the result to compare with the project WBS.


  1. CSI OmniClass (2010), OmniClass A Strategy for Classifying the Built Environment. Retrieved from www.omniclass.org
  2. Humphreys, Gary, C. (2011). Project Management Using Earned Value.Orange,CA: Humphrey & Associates, Inc.
  3. Sullivan, G., William, Wicks, M., Elin, Koelling, Patrick, C. (2009), Engineering Economic, Fifteenth Edition. Pearson International Edition, 2012

1 thought on “W3_GGS_OmniClass WBS Table Selection Using Additive Weighting Technique

  1. Excellent, Gustaf!!! Nice work. The only thing that kept you from earning an AWESOME was why didn’t you explain your selection critria?

    I can understand how Table 22, with a score of 0.90 or Table 23, with a score of 0.87, but why did you include Table 21 with only a score of 0.60?

    Had you written a couple of sentences explaining how or why you chose the selection criteria you did, it would have been a MUCH better posting…..

    Keep up the good work, but PLEASE get in the habit of following the step by step process. Come exam time, you will thank me 1000 times over!!!

    Dr. PDG, Jakarta

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