Nowadays, social networks play significantly important roles in everyday life. People produce various sorts of content and consume huge amounts of events at the same time. Actually, it has already weaved into the fabric of everyday life seamlessly. With the prevalence of Twitter, Sina Weibo, Facebook etc., they pose challenges to the traditional media companies and institutes because they react fast and the topic have been propagated through underlying dynamics in real time. There are many interesting research questions raised. Detecting online communities from a given small group of people could help us to understand who will involve in a specific group . Topical link or social link prediction and recommendation would facilitate the process of searching related topics or users . Meanwhile, emerging hot topics attract more eyeballs and it is pretty important to rank emerging topics and predict the trend . Rather than identifying the specific topics, how to explain the information propagation over dynamic networks and figure out the key paths and spreaders still pose challenges . Generally speaking, there are more topics to explore rather than listed above. But in this proposal, the points should be focused on the understanding of information propagation over particular topic set. Capturing related data, discovering underlying patterns and visualization should facilitate the journey to unknown world. A framework should be established to demonstrate the idea. There are five parts to construct a coherent and reasonable project, including data crawling, pre-processing, model mapping and semantic affiliation, pattern mining and visualization .
There should be sufficient data so that the distribution of the topic can be represented by the sample from data crawling.
In the process of pre-processing, dirty data should be cleaned and missing value should be given a proper value or the sample with missing value should be discarded.
An appropriate model with sufficient enough semantic information support to describe the topic.
As we discussed in literature review, traditional pattern mining methods AGM , FSG , GSPAN  and FFSM  might be costly to deal with large sub-graph patterns. Both SPIN  and MARGINI  are introduced to mine maximum frequent subgraphs. But they are still costly in the context of large subgraphs mining. ORIGAMI  is introduced to extract a representative set subgraphs. LEAP  aims to find most significant patterns directly. GREW  is designed to overcome the limitations of existing complete or heuristic frequent subgraphs discovery algorithm. One of the most recent work is SpiderMine  ,which is designed to find the top-K largest patterns with a high probability. Unfortunately, ORIGAMI, LEAP, GREW, SpiderMine can’t not process large graphs with constrains. GPRUNE  discusses pruning in both pattern space and data space, which is possible to improve the performance of large pattern discovery with constrains. SKINNYMINE , proposed by Zhu etc. , gains insights of the properties of constraints of long backbone with short twigs. In the context of social network service, constrains should be considered and GPRUNE  and SKINNYMINE  can be treated as baseline methods in the study. The challenge of topic propagation is to identify specific constrains and mine the most significant sub graphs effectively.
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This work was carried out at the International Doctoral Innovation Centre (IDIC). The authors acknowledge the financial support from Ningbo Education Bureau, Ningbo Science and Technology Bureau, China's MOST, the University of Nottingham, and Simon See. The work is also partially supported by EPSRC grant no EP/L015463/1.