abstract Service
    requirements : Requirements  // resources required by a service
    machine -> Machine          // machine the service is allocated to 
    [this in machine.services]  // inverse relationship constraint

abstract Requirements
    morning_cpu -> integer
    midday_cpu -> integer
    evening_cpu -> integer
    night_cpu -> integer

abstract Resources
    cpu -> integer

abstract Machine
    services -> Service*        
        [this.machine = Machine]
        
    isFree? 
    [isFree <=> no services]

    limits : Resources

/* constraints for limiting total requirements */

    morning_utilization : Resources
        [cpu = sum services.requirements.morning_cpu]
        [cpu < limits.cpu]

    midday_utilization : Resources
        [cpu = sum services.requirements.midday_cpu]
        [cpu < limits.cpu]

    evening_utilization : Resources
        [cpu = sum services.requirements.evening_cpu]
        [cpu < limits.cpu]

    night_utilization : Resources
        [cpu = sum services.requirements.night_cpu]
        [cpu < limits.cpu]

Task   
    // total number of machines free
    total_free -> integer = #Machine.isFree
<<max Task.total_free>>

GoogleCA : Machine
    [limits.cpu = 10]

GoogleNY : Machine
    [limits.cpu = 16]

GoogleTX : Machine
    [limits.cpu = 14]

MailService : Service
    [requirements.morning_cpu = 5]
    [requirements.midday_cpu = 4]
    [requirements.evening_cpu = 5]
    [requirements.night_cpu = 1]

SearchService : Service
    [requirements.morning_cpu = 7]
    [requirements.midday_cpu = 7]
    [requirements.evening_cpu = 8]
    [requirements.night_cpu = 3]

CalendarService : Service
    [requirements.morning_cpu = 2]
    [requirements.midday_cpu = 2]
    [requirements.evening_cpu = 2]
    [requirements.night_cpu = 1]