4D technology is a current fact and challenging visualization medium for project planning.  It will be very important for such type of studies to extend 4D research in further directions. The authors cover tremendously a great body of literature necessary for the study. However, there are some questions this research & case study did not answer clearly, they are summarized below:
- How was the critical activities in the schedule affected the study in the decision to develop the 4D model?
- The author mentions in Section (2.1) 3D CAD models lack necessary detail information like temporary work. The reader will expect to see such information being modeled in the current case study to extend on previous 4D research. None of the Figures presented actually illustrates this implementation.
- It is understood that the purpose of 4D development in this work should help planners in validating complex activity sequences (section 5). This is a major challenge indeed. It will be argued that for a simple rectangular shape building, sequencing ground floor slab before the upper floor slabs is a simple activity. I can guess (and not being critical) that the case study should highlight more real conflicts between complex activities. For example, previous 4D researchers highlighted sever conflicts as result of M&E work package and other activities. It is, as the author mentioned, common practice to construct building from the ground up to the roof!
- Section (8.1). What was the extra level of detail developed for PCC slab work package? The illustration figures do not seem to show such level of detail. This is a challenging 4D model production technique and it will be very interesting if more visual illustration is provided to show the level of detail in the project schedule and product model. The explanation is too general be or real benefit to the reader.
- Section (10): that current 4D tools like Common Point, Graphisoft 5D Constructor, NavisWorks Time Liner, etc. are being used by contractors and have support to all these features.
Genera notes on language and clarity of paper writing:
- Section (2.2) paragraph 1: use ‘… his/her…’ instead of ‘… a planner uses its own…’.
- Section (11, i) tackles a valid problem in current industry that is the lack of technical skills future planners. Please replace ‘… 4D planning is a profession..’ with ‘… 4D planners’.
- The second conflict visualization and resolution mentioned in Section (8.2) is not clear. It is perhaps easier if the author provides additional illustration showing the detailed level 4D model showing the foundation work package and the sub-assembling of its components. Has this been reflected in the construction schedule too?
