Replace data in Jena

[Mikael Pesonen]

Hi,
I want to change all dcterms:abstract to dcterms:description in a graph. 
Following update query doesnt do anything in Fuseki UI (using 
fuseki/ds/update):

PREFIX dcterms: <http://purl.org/dc/terms/>


DELETE { ?s dcterms:abstract ?o }

INSERT { ?s dcterms:description ?o }

WHERE

{

 GRAPH  <somegraph> {

 ?s dcterms:abstract ?o

}}

So I must be doing something wrong here?

Br,
Mikael