## 3 Research Scope and Methodology
### Study Methodology  
In order to establish a BIM-based VDI environment, firstly, physical hardware should be built. Specifications of VDI hardware requirements are greatly affected by how they are assessed, measured, and sized. Therefore, a reasonable and adequate method of measurement is imperative to properly size the VDI hardware requirements. This hardware sizing, in general, can be done using three different methods: the calculating method, the referencing method, and the simulation technique. Their characteristics, advantages, and disadvantages are summarized in Table 4.  
Among these three methods for hardware sizing, the calculating method calculates figures of volume based on factors for sizing, and then applies corrected values, which gives it an advantage in that it can provide an accurate rationale for sizing. However, a large difference may occur depending on the correction value applied. The referencing method generates a similar scale of hardware specifications in comparison with an approximate scale of the system, based on basic data including workload (the number of users, and DB sizes). It provides a great deal of reliability by making it possible to calculate sizes in a relatively safe fashion, because comparison can be made with work systems that were previously established. On the other hand, as it uses comparison rather than calculation, it falls short of presenting sufficient grounds for comparison under different environments, which is a drawback. The simulation technique performs modeling of workload for the applicable work, simulates it, and then estimates sizes. The positive side of this method is that it can produce accurate values when compared to both the calculating method and the referencing method, however, it takes a great deal of time and money to calculate. In general, not only hardware, but also software and networks should be subject to sizing, but the study on Integrated Standards for Information System Sizing [29] specified that only hardware is subject to sizing because the influence of the others is insignificant. Although hardware is composed of various components, three items in particular, including CPU, RAM and disk space, are defined as subject to sizing due to their importance in terms of system price and performance. As such, this study also considered these three components in sizing the VDI hardware. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Division** & **Characteristic** & **Advantage** & **Disadvantage** \\ \hline \multirow{4}{*}{Referencing Method} & Checking similar scale by comparing rough system scale based on basic data dependent on business volume & Relatively safe scale could be estimated as comparison with existing & Not a calculation method, but a comparison \\ \hline \multirow{4}{*}{Calculating Method} & A method of calculating numerical scale and applying correction value based on elements for calculating scale including & Ground of scale estimation could be clearly presented and it could be estimated more simply compared with other methods & If the correction value is incorrect, there is a considerable difference from the desired value \\ \hline \multirow{4}{*}{Simulation Technique} & Scale is estimated by modeling work load for the target business and simulating it & Relatively accurate value could be obtained & Time-consuming and costly \\ \cline{1-1} \cline{2-4}  & & & \\ \cline{1-1} \cline{2-4}  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Server sizing method. It is difficult to utilize the simulation technique for the BIM project because it requires considerable time. Therefore, this study established a VDI system optimized for BIM users by combining both the referencing method and the calculating method. The higher volatility in the calculation method was corrected by adding the higher reliability of the referencing method, while the accurate grounds were presented to compensate for the insufficient grounds of the referencing method by applying factors of the calculating method.