This process for managing meeting for large groups of people was developed by Harrison Owen. It has been for groups as large as 2,000 people and run over several days.

Open Minded Days uses a subset which lasts a day and which works for group of between 30 and 300 people.

The first objective is to get people discussing topics related to the theme.

The second objective is draw some conclusions from that discussion.

The third objective is to take some action if that is within the remit of those in the discussion or to coomunicate with those who can.

Brief details of the elements of Open Space are provided here.  More informatin can be found on Wikipedia or in Harrison Owen's book.