## 3 Proposed Method
### Overall Procedure
#### 3.2.2 Structured Data Analysis  
The values of the technological novelty (VON) of a technology manifested in a patent are determined using a novel map of technology changes over time, based on structured data of the patent set, as shown in Figure 4. This reveals the emergence of new technologies. A three-step process is introduced to draw a map for calculating VON, as follows:  
Figure 2: Framework for identifying technological opportunities of radical inventions.  
Figure 4: A map of technological changes over time.  
Figure 3: Structure of the description section of a Chinese invention.  
1. Fill in an IPC/date matrix, as shown in Table 1. The application dates are in the first column of the matrix (the date interval can be yearly, quarterly, monthly, etc.), and the IPC symbols of each patent in the patent collection are in the first row. The number of patents that meet both the application date and IPC symbol is placed in the corresponding position in the matrix. The application date set is Y = {Y1, Y2, Y3,..., Yi,..., Yi,..., YM} and the IPC symbol set is IPC = {IPC1, IPC2, IPC3,..., IPCm,..., IPCm}.
2. Use the IPC/date matrix as the input to a map of technological changes over time. Use application year as the time interval for illustration. The nodes in the map are all IPC symbols, to which patents belongs in the first year and new IPC symbols in each subsequent year. Then, the nodes distributed in different years are connected, and connections are weighted based on the difference between pairwise IPC symbols. The difference is marked as D\({}_{n(y\times i)}\), its value represents the degree of difference between the IPC\({}_{j}\) and IPC\({}_{i}\), where \(j>i\) and IPC\({}_{j}\) appear for the first time in Y\({}_{n}\). Assign values based on the following rules: D\({}_{n}\) is 2 if the difference exists only in the last English letter between two IPC symbols, 3 for the same chapter symbols, and 4 for inconsistent chapter symbols.
3. The degree of novelty set of IPC symbols is Nd = {Nd1, Nd2, Nd3,..., NN}. The degree of novelty of an IPC symbol depends on both its difference from existing IPC symbols and the year when it first appeared, which can be decided as: \[\text{Nd}_{y}=\text{Y}_{i}+\text{min}\{\text{D}_{y(i\times(i\text{-}1))}, \text{D}_{y(i\times(i\text{-}2))},\ldots,\text{ D}_{y(i\times 2)},\text{D}_{y(i\times 1)}\},\] (1) where \(y\) is the mark of an IPC that first appeared in year \(i\). Therefore, the larger the Nd\({}_{x}\), the higher the degree of novelty of IPC symbols.  
Taking Figure 4 as an example, G01C first appeared in 2010, so the degree of novelty of G01C is Nd\({}_{1}\) = Y\({}_{1}\) + D\({}_{1}\) = 1 + 1 = 2. In the second year, only F16M emerged; thus, the degree of novelty of F16M is Nd\({}_{2}\) = Y\({}_{2}\) + D\({}_{2(2\times 1)}\) = 2 + 4 = 6. No new IPC symbols originated in 2012, and G03B and F16F arose in 2013; therefore, the degree of novelty of G03B is Nd\({}_{3}\) = Y\({}_{4}\) + min[D\({}_{3(3\times 1)}\), D\({}_{3(3\times 2)}\)] = 4 + min[4, 3] = 4 + 3 = 7; and the degree of novelty of F16F is Nd\({}_{4}\) = Y\({}_{4}\) + min[D\({}_{4(4\times 1)}\), D\({}_{4(4\times 2)}\)] = 4 + min[4, 2] = 4 + 2 = 6. The results show that there are three categories: G01C that appears first, F16F and F16M with higher values of technological novelty (VON), and G03B with the highest VON.