{ identifier: 'name',
   items: [
     { name:'Africa', type:'continent',
         children:[{reference:'Egypt'}, {reference:'Kenya'}, {reference:'Sudan'}] },
     { name:'Egypt', type:'country' },
     { name:'Kenya', type:'country',
         children:[{reference:'Nairobi'}, {reference:'Mombasa'}] },
     { name:'Nairobi', type:'city' },
     { name:'Mombasa', type:'city' },
     { name:'Sudan', type:'country',
         children:{reference:'Khartoum'} },
     { name:'Khartoum', type:'city' },
     { name:'Asia', type:'continent',
         children:[{reference:'China'}, {reference:'India'}, 
{reference:'Russia'}, {reference:'Mongolia'}] },
     { name:'China', type:'country' },
     { name:'India', type:'country' },
     { name:'Russia', type:'country' },
     { name:'Mongolia', type:'country' },
     { name:'Australia', type:'continent', population:'21 million',
         children:{reference:'Commonwealth of Australia'}},
     { name:'Commonwealth of Australia', type:'country', population:'21 million'},
     { name:'Europe', type:'continent',
         children:[{reference:'Germany'}, {reference:'France'}, {reference:'Spain'}, {reference:'Italy'}] },
     { name:'Germany', type:'country' },
     { name:'France', type:'country' },
     { name:'Spain', type:'country' },
     { name:'Italy', type:'country' },
     { name:'North America', type:'continent',
         children:[{reference:'Mexico'}, {reference:'Canada'}, {reference:'United States of America'}] },
     { name:'Mexico', type:'country',  population:'108 million', area:'1,972,550 sq km',
         children:[{reference:'Mexico City'}, {reference:'Guadalajara'}] },
     { name:'Mexico City', type:'city', population:'19 million', timezone:'-6 UTC'},
     { name:'Guadalajara', type:'city', population:'4 million', timezone:'-6 UTC' },
     { name:'Canada', type:'country',  population:'33 million', area:'9,984,670 sq km',
         children:[{reference:'Ottawa'}, {reference:'Toronto'}] },
     { name:'Ottawa', type:'city', population:'0.9 million', timezone:'-5 UTC'},
     { name:'Toronto', type:'city', population:'2.5 million', timezone:'-5 UTC' },
     { name:'United States of America', type:'country' },
     { name:'South America', type:'continent',
         children:[{reference:'Brazil'}, {reference:'Argentina'}] },
     { name:'Brazil', type:'country', population:'186 million' },
     { name:'Argentina', type:'country', population:'40 million' },
]}