  Semantic communication is not focused on improving the accuracy of
transmitted symbols, but is concerned with expressing the expected meaning that
the symbol sequence exactly carries. However, the measurement of semantic
messages and their corresponding codebook generation are still open issues.
Expansion, which integrates simple things into a complex system and even
generates intelligence, is truly consistent with the evolution of the human
language system. We apply this idea to the semantic communication system,
quantifying semantic transmission by symbol sequences and investigating the
semantic information system in a similar way as Shannon's method for digital
communication systems. This work is the first to discuss semantic expansion and
knowledge collision in the semantic information framework. Some important
theoretical results are presented, including the relationship between semantic
expansion and the transmission information rate. We believe such a semantic
information framework may provide a new paradigm for semantic communications,
and semantic expansion and knowledge collision will be the cornerstone of
semantic information theory.
