Among many clustering algorithms, the K-means clustering algorithm is widely used because of its simple algorithm and fast convergence. However, the K-value of clustering needs to be given in advance and the choice of K-value directly affect the convergence result. To solve this problem, we mainly analyze four K-value selection algorithms, namely Elbow Method, Gap Statistic, Silhouette Coefficient, and Canopy; give the pseudo code of the algorithm; and use the standard data set Iris for experimental verification. Finally, the verification results are evaluated, the advantages and disadvantages of the above four algorithms in a K-value selection are given, and the clustering range of the data set is pointed out.

Interconnection between multiple data link systems is an urgent problem for wireless control systems. Its difficulty lies in the fact that data link messages are multi-source heterogeneous, By analyzing its sub-domain characteristics, we constructs the data message domain ontology and establishes a data link message ontology model based on Bayesian network(DLMOBN). It includes the study of nodes, directed edges and node similarity probability distribution and so on, convert multi-source heterogeneous messages into mathematical models. We propose a data link message ontology mapping algorithm, the OWL syntax is used to formally describe the acquired domain ontology, extract useful information such as concepts, attributes, and instances, and then store the information in a preset data structure, k-means algorithm is used to cluster them to form ''cluster'', which is used as a classification index to classify the similarity pair as a node in the Bayesian network, and pass the concept of the lower layer between nodes to the prior concept of the upper layer. The semantic distance, the attribute, the feature and other factors of the similar pair are used to calculate the semantic similarity. Finally, the final semantic similarity value is obtained by weighting. It is verified by experiments that the method improves the recall rate and precision, reduces the time complexity.