Why isn't the 'volume' field always populated in XigniteGlobalIndices?

Is there an option to return Xignite data in JSONP format? What Security Identifiers does Xignite APIs support? Can Xignite APIs be called from multiple locations? Does Xignite charge per API call? Is it possible to point to an Xignite IP address instead of an URL? What is the maximum number of symbols (or identifiers) supported in Xignite APIs? What is a Xignite API Token? Can I call Xignite APIs securely? Does Xignite support CUSIP? Does Xignite support FIGI? What is CompositeIdentifier? What is “automatic identifier stitching”? What is IdentifierAsOfDate? At what time are mutual fund NAVs available? When are dividends available under Xignite APIs in relation to their Ex-Date? Does the IPO share count number include underwriter options? Are the treasury rate figures published in XigniteMoneyMarkets and XigniteRates yields or discount rates? Why isn't the 'volume' field always populated in XigniteGlobalIndices? Can I use Xignite's technology to eliminate terminals?