## 5 Discussion  
In sum, the roadmapping framework that we have built could be analyzed from three essential parts that cover the features of the proposed approach. The first part lies in the nodes which are set to depict the implication of extracted technology or product. Research by [PERSON] et al. [2] defined nodes by the aid of patent document while research by [PERSON] and [PERSON] [78] utilized the concept of scenarios in order to build nodes. In comparison, we built nodes in Tables 5 and 7 with the aid of keyword-based MA which could decompose target fields hierarchically and systematically similar to [PERSON] et al. [4]. Secondly, the linkage between layers is essential to analyze. The pair of nodes with a high similarity value indicates a high probability to conduct coordinated development, which was depicted in Tables 6, 8 and 9. Researches by [PERSON] et al. [79] and [PERSON] et al. [4] established the linkage between technology and product layer based on the technology-product link matrix, evidencing that the relationship between technology and product layer could be measured by the similarity. Thirdly, the process of identifying new opportunities from existing TRM is established in a novel way. The process refers to two aspects. One relates to the analysis of the technology and product development trends in a dynamic perspective based on SGTM map. [PERSON] [73] modified the conventional GTM algorithm and achieved simultaneous data visualization and clustering in a dynamic perspective, which is utilized in this study to identify sparse and dense innovation areas. The other one refers to the application of TRIZ inventive principles. Research by [PERSON] [80] confirmed the validity of integration between TRIZ and TRM, in which the evolutionary patterns of technical systems are utilized to elaborate the structure and composition of TRM. In this study, TRIZ inventive principles are particularly introduced in order to impact on the innovation elements derived from innovation sparse areas. As can be seen in Table 11, six new technology and product opportunities in the technology-product MA-based TRM are derived from the sparse areas in a hybrid way which contains quantitative and qualitative tools. New technologies hasten new products, while the related conception of new products will promote the development of new technologies accordingly. For example, as an alternative material, the usage of titanium metal could improve the mechanical performance of underwater vehicles to a certain extent. As for the practical production, it will depend on the level of technology development, which is related to production cost. The derived new opportunities represent a development trend to direct the organizations to plan technology and product strategy. Therefore, how to utilize the discovered new opportunities in practical production is another important decision making aspect. It should be noted that the application of each opportunity is not mandatory, since whether a firm prevent all kinds of unexpected things or not is simply a matter of decision, if a firm does not possess enough resources and capabilities. Traditional MA-based TRM provides a standard form to utilize morphology configuration to identify technology opportunities. [PERSON] et al. [4] established the morphological matrix of mobile phone technologies and products mainly based on expert's participation and identified technology opportunities by substituting the components of technology and product configurations. Compared with that, the results of this article reveal the technology and product development trends with a further quantitative analysis in the identification of sparse and dense innovation areas, which make the process of identifying new opportunities systematic. According to the technology and product trends, we define new opportunities by the aid of TRIZ inventive principles. Several policies of the proposed approach are worth noting.