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In Odysseus go to the "Project Explorer" and open "Import.." from the context menu (right click with your mouse).
Choose "Existing Project into Workspace" from the "General" folder and click on "Next". Choose "Select archive file" and "Browse..." for the downloaded "NexmarkProject.zip" in your filesystem. You should see "Nexmark" in the "Projects:" field like here:
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You can also have a look at the query plan to investigate the running operators by hiting the "Active graph" command:
Then you should get a view like:
That's all. Now you can, for example, express your own queries using Odysseus Script
See this tutorials for some examples projects explaning Odysseus.