global class InvoiceWebService 
{

 webService static Id generateQuote( Id OpportunityId )
 {
  List< OpportunityLineItem > oli = new List< OpportunityLineItem >();
  oli = getOpportunityLineItems( OpportunityId );
  
  Opportunity o = [select id, accountid, type, stageName from Opportunity where id = :OpportunityId];
  
  Account a = [select id, type, customer_id__c, maintenance_expiration_date__c, asp_expiration_date__c from Account where id = :o.AccountId];
  
  if ( o.type == 'Standard' )
  {
   if ( hasMaintenanceOpportunityProducts( oli ) == false )
   {
    // Do something  
   }
  }
  
 }
 
 //////////////////////////////////////////////////////////////
 // Private helper functions for the webservice
 //////////////////////////////////////////////////////////////
 
 private List< OpportunityLineItem > getOpportunityLineItems( Id OpportunityId )
 {
  // Reduced the SQL command to allow it to be viewable in this thread.
  return [select FIELDS from OpportunityLineItem o where o.OpportunityId = :OpportunityId ];
 }
 
 private Boolean hasMaintenanceOpportunityProducts( List< OpportunityLineItem > oliItems )
 {
  Boolean hasMaintenance = false;
  
  for ( OpportunityLineItem oliTemp : oliItems )
  {
   if ( oliTemp.PricebookEntry.Product2.Family == 'Maintenance' )
    hasMaintenance = true;
  }
  
  return hasMaintenance;
 }
}