## 2 Related Works
### Discussion  
Table 1 compares the BVMO proposed in this study with those of related studies.  
The categories adopted for comparison listed in Table 1 are as follows: (1) whether the resource-provisioning domain is introduced and utilized in the study; (2) whether there is a method or mechanism for reusing cloud resources; (3) whether there is a description of the technique through the system architecture; (4) whether there is a plan for multi-cloud support; and (5) support measures for providing VMs tailored to user needs.  
Table 2 presents the comparison of the IaC tools, cloud-platform-management tools and BVMO.  
As listed in Table 2, the subjects of comparison with the BVMO presented in this study are each components of OpenStack, which is used as an open-source private cloud platform, and the main element of the Hasicorp Software Stack, which performs automation and distributed control of multi-cloud. The vault of the Hashicorp Software Stack performs security related to authentication processing scattered across multiple clouds, Consul controls cloud networking resources through service discovery and Nomad performs service utilization and control through a Remote Procedure Call (RPC). In this stack, the platform deployment and execution of each software package are implemented as templates based on Terraform.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Study** & **Resource Provisioning** & **Resource** & **Methodology System** & **Multi-Cloud** & **Customized** \\  & **Domain?** & **Reuse?** & **Architecture?** & **System Support?** & **VM?** \\ \hline [PERSON] et al. [23] & ✓ & & ✓ & & \\ [PERSON] et al. [24] & ✓ & & ✓ & & ✓ \\ [PERSON] et al. [25] & ✓ & ✓ & ✓ & & \\ [PERSON] et al. [26] & & & ✓ & ✓ & \\ [PERSON] et al. [27] & & ✓ & ✓ & ✓ & ✓ \\ Our method & ✓ & ✓ & ✓ & ✓ & ✓ \\ \hline \hline \end{tabular}
\end{table}
Table 1: Literature Review of Related Studies.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Software Set** & **Specific** & **Software** & **Platform Boundary** & **Implement** & **Coverage** \\ \hline \hline \multirow{8}{*}{Hashicorp Software Stack [29]} & Terraform [28] & IaC & & Template & Cloud platform \\  & & & & & elements deployment \\ \cline{2-5}  & Vault [31] & Security & Multi cloud & Template & Cloud platform \\  & & & & domain where & \\ \cline{2-5}  & Consul [32] & Networking & automation engine & & \\  & & & & & networking strategy \\ \cline{2-5}  & Nomad [33] & Application & & & \\ \cline{2-5}  & Heat [30] & IaC & & Template & OpenStack platform \\  & & & & & elements management \\ \cline{2-5}  & Keystone [34] & Authentication & & & \\ \cline{2-5}  & Neutron [35] & Networking & & & \\ \cline{2-5}  & Nova [36] & Instantiation & & & \\ \hline \hline \multirow{3}{*}{Our Study} & \multirow{3}{*}{BVMO} & VM resource & Multi-cloud platform & & Cloud platform instance \\  & & & & & management for more \\ \cline{1-1}  & & & & & reusability and \\ \cline{1-1}  & & & & & flexibility \\ \hline \hline \end{tabular}
\end{table}
Table 2: Review of Related Technologies.  
Additionally, on the OpenStack Components side, Keystone creates and assigns permission to access the platform, configures and controls instance networks through Neutron, and creates and controls cloud instances through Nova. The distribution and flow control of these components can be achieved using heat templates.  
In contrast, the BVMO in this study is a system that creates and reconfigures VMs by combining cloud resources extracted from multiple private clouds using IaC and supports deployment to specific locations in multiple clouds. In addition, the various tools compared above require prior knowledge of APIs or templates rather than system control through a dashboard for smooth use. However, because the BVMO presented in this study provides the basic flow of combining pre-established resources with the user's choice, compared to other tools, the BVMO is technically accessible and simple to use.