## 3 Identifying Promising Vacant Technologies
### Detailed Procedures
#### 3.2.2 Technical Analysis of Vacant Technology Field through Criticality and Trend Analyses  
After identification of the vacant technology field, the second step focuses on determining if it holds promise through two substeps: criticality analysis and trend analysis. (Figure 3).  
Figure 2: The process of identifying vacant technology fields.  
To design practical R&D planning, it is necessary to investigate the prominent characteristics of the vacant technology and identify the related trends. To understand a technology's potential, it is necessary to evaluate the current level of technology and predict its prospects [59; 60; 61]. Therefore, we performed a criticality analysis through a technology level map to evaluate the current technology level and a time series analysis to predict prospects.  
A criticality analysis aims to assess the current technological level by using a map that evaluates the relative level of technology. This technology level map uses the number of patent applications as a quantitative evaluation criterion and the number of patent claims as a qualitative evaluation criterion [59]. Its \(X\)-axis represents the technology activity index (TAI) for the relative quantitative valuation of technology. As more patents are applied for, it shows that a technology is growing rapidly [62]. The \(Y\)-axis represents the technology impact index (TII) for the relative qualitative valuation of the technology. The number of claim items is suitable as an evaluation index of the effect of technology because it represents the scope of patent validity [63]. Therefore, we performed a criticality analysis using a technical level map to evaluate the current level of vacant technology fields. The technical fields can be located in the 1, 2, 3, and 4 quadrants of the map. The 1 quadrant is defined as the high level where both the TAI and TII indicators are high, and the 2 and 3 quadrants are defined as the medium level where either the TAI or TII indicator is high. Finally, the 4 quadrant is defined as the low level where both indicators are low.  
A trend analysis aims to forecast the future of a technology field. A time series analysis is a method of predicting values using historical data obtained continuously at regular intervals over time. Time series data is composed of viewpoints and frequency; the viewpoint is the independent variable, and the frequency is the dependent variable. The predicting value is then determined using a statistical method. Due to various environmental variables, a time series analysis is more suitable for short- and medium-term perspectives than for long-term perspectives [64]. There are various predictive analysis models for time series analysis. In this study, we apply the ARIMA model, which reflects the autocorrelation of previous values affecting subsequent values, the effects of random variables over time, and trends in historical data to analyze trends analysis in technical fields Based on the trend analysis results, we defined the rising technical field as hot field, the decreasing technical field as cold field, and the stable technical field as active field [65; 66].  
Figure 3: Technical analysis of a vacant technology field.