Having worked in the public sector (and quasi-public sector) including building a KM program, I'd suggest that KM tools / systems aren't different there.

They are related to the nature of the business problem that you are trying to solve (e.g. a call centre's KM problems are the same whether it is public or private; complex knowledge work is the same whether it is lawyers in a law firm or policy advisors in Cabinet Office).

G
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Gordon Vala-Webb
Building Smarter Organizations
How to lead your zombie organization back to life