# An Ontology for Spatio-Temporal Media Management and an Interactive Application
## 8 Discussion and Conclusions  
In this paper, we proposed the SDM Ontology Version 2, an ontology of spatio-temporal media that can comprehensively and precisely describe events and their semantic information in real space. The SDM Ontology can structurally describe spatio-temporal media, which describes positional and temporal information in 3D space as a whole, and their related equipment, processing, and semantic information. By taking advantage of this feature, the SDM Ontology is expected to become a digital media management framework that comprehensively describes the workflow of digital media from recording, processing, and editing to playback and the related semantic information. The SDM Ontology is an ontology for realizing digital media suitable for providing interactive and highly realistic viewing experiences in AR/VR applications, which are expected to become popular. We have created a dataset based on the recorded data of jazz band and classical orchestra concerts in accordance with SDM Ontology Version 2 and confirmed that the dataset could comprehensively describe a large number of recorded media and a variety of metadata. Furthermore, we developed a web-based VR application (Web360\({}^{2}\)) to reproduce concerts by referring to this dataset and showed that it is possible to realize an interactive application that can reproduce a high sense of presence based on the dataset described by the SDM Ontology. In addition, from the results of the subjective evaluation of the Web360\({}^{2}\), it was estimated that the network and rendering speed were generally satisfactory in a PC environment. At the same time, the performance was insufficient for tablets and smartphones, and hence we discussed the performance requirements of these devices. These results demonstrate that the SDM Ontology Version 2 has the potential to serve as a framework for digital media management, but the scope identified in this work is limited, and more use cases need to be tested by creating data sets to confirm its effectiveness. A website ([[https://tlab.hongo.wide.ad.jp/sdmo/](https://tlab.hongo.wide.ad.jp/sdmo/)]([https://tlab.hongo.wide.ad.jp/sdmo/](https://tlab.hongo.wide.ad.jp/sdmo/)) (accessed on 1 June 2023)) for the SDM Ontology in Japanese has already been created, but the English version is still in progress and we would like to develop it. In addition, many research issues remain to be addressed. Expanding the definition of the SDM Ontology and reducing the burden of dataset creation are critical issues. The definition of SDM Ontology version 2 still needs to be revised to realize the specified design policy (Section 3.1). The **Recorder**, **Processor** and **Player** classes still define only essential functions and lack information to describe the workflow from recording to playback. It will be necessary to extend the definitions so that the **Recorder**, **Processor** and **Player** classes can describe the equipment and programs that performed the respective processes and their configuration information. The **CoordinateSystem** class definition is a provisional version, and the detailed definition needs to be completed. Descriptions of the coordinate system origin, the direction of the coordinate axes, and the definition of the derived coordinate system are the essential requirements items described in Section 3.1. This functionality is essential for describing media data and metadata handled in the coordinate transformation processes. By enhancing these definitions, it will be possible to describe a series of workflows from media recording, processing, and editing to playback in a dataset. As a result, it is expected that media management will become more sophisticated and include automation of the data processing and tracking of the processing history. Another issue is to reduce the workload of dataset creation. As mentioned in Section 4.2, creating a dataset requires recording many video and audio media, processing and editing them, and collecting the metadata to connect them or add semantic information.