SubGraph

This allows you to define a graph within the graph. This will group those objects together in some engines.

 graph g {
    subgraph 0 -Attributes @{label='DMZ'} {
        node web1,web2,reports
        edge report -To web1,web2
    }        
    edge loadBalancer -To web1,web2
    edge user -To loadBalancer,report
    edge web1,web2,report -To database
}

ID requirements

One special requirement of the subgraph is that it needs a numerical ID. They need to sequential starting from 0.

This does allow you to define parts of the same subgraph in different sections if needed.

graph g {
    subgraph 0 -Attributes @{label='DMZ'} {
        node web1,web2            
    }  
    edge report -To web1,web2      
    edge loadBalancer -To web1,web2
    edge user -To loadBalancer,report
    edge web1,web2,report -To database
    subgraph 0 {
         node report
    }
}