A UsageVolumeProductSpec is a type of AtpmicProductSpecification.<br/>It represents a predefined quantity of product usage (aka bucket), like a 2 hours national calls, often known as an Allowance.<br/>It could be either a quantity or an amount in a currency (i.e. It could represent a fixed number of SMS, MMS, minutes of calls, Quantity of data as well as a specific amount in € …).<br/>A UsageVolumeProductSpec requires one or many NetworkProductSpecs from which Usages will debit the bucket.<br/>A UsageVolumeProductSpec also defines UsageVolumeChargingRules specifying how to decrement the bucket.<br/>A NetworkProductSpec might be monitored or not. The wording monitored means that the user can’t realise a type of usage if he hasn’t any FixedVolumePackageProd for this type of usage (i.e. without an empty balance). In this case, the attribute isUsageMonitoring is TRUE.<br/>