  Semantic communication is widely touted as a key technology for propelling
the sixth-generation (6G) wireless networks. However, providing effective
semantic representation is quite challenging in practice. To address this
issue, this article takes a crack at exploiting semantic knowledge base (KB) to
usher in a new era of generative semantic communication. Via semantic KB,
source messages can be characterized in low-dimensional subspaces without
compromising their desired meanings, thus significantly enhancing the
communication efficiency. The fundamental principle of semantic KB is first
introduced, and a generative semantic communication architecture is developed
by presenting three sub-KBs, namely source, task, and channel KBs. Then, the
detailed construction approaches for each sub-KB are described, followed by
their utilization in terms of semantic coding and transmission. A case study is
also provided to showcase the superiority of generative semantic communication
over conventional syntactic communication and classical semantic communication.
In a nutshell, this article establishes a scientific foundation for the
exciting uncharted frontier of generative semantic communication.
