  We introduce KOSMOS, a knowledge retrieval system based on the constructed
knowledge graph of social media and mainstream media documents. The system
first identifies key events from the documents at each time frame through
clustering, extracting a document to represent each cluster, then describing
the document in terms of 5W1H (Who, What, When, Where, Why, How). The event
centric knowledge graph is enhanced by relation triplets and entity
disambiguation from the representative document. This knowledge retrieval is
supported by a web interface that presents a graph visualisation of related
nodes and relevant articles based on a user query. The interface facilitates
understanding relationships between events reported in mainstream and social
media journalism through the KOSMOS information extraction pipeline, which is
valuable to understand media slant and public opinions. Finally, we explore a
use case in extracting events and relations from documents to understand the
media and community's view to the 2020 COVID19 pandemic.
