Revenue RecognitionWe generate revenue by providing software as a service ("SaaS") solutions through on-demand subscription, on-premise perpetual and term licenses and related software maintenance, and services. Amounts that have been invoiced are recorded in accounts receivable and in deferred revenue or revenue, depending on whether the revenue recognition criteria have been met. Recurring Revenue. Recurring revenue, which includes SaaS revenue and maintenance revenue, is recognized ratably over the stated contractual period. SaaS revenue consists of subscription fees from customers accessing our cloud-based service offerings. Maintenance revenue consists of fees from customers purchasing licenses and receiving support for such on-premise solutions. We also recognize SaaS and maintenance revenue associated with customers using our solutions in excess of contracted usage ("Overages"). Overages are primarily attributed to SaaS products and are recorded in SaaS revenue in the period incurred. Revenue related to Overages was immaterial for all years presented.Service and License Revenue. Service and license revenue primarily consists of services revenue related to training, integration and configuration services. Our professional services arrangements are generally billed on a time-and-materials basis. Time and material services are recognized as the services are rendered based on inputs to the project, such as billable hours incurred. For fixed-fee professional services arrangements, we recognize revenue under the proportional performance method of accounting and estimates the proportional performance on a monthly basis, utilizing hours incurred to date as a percentage of total estimated hours to complete the project. If we do not have a sufficient basis to measure progress toward completion, revenue is recognized upon completion. Service and license revenue also includes revenue from perpetual licenses, which is recognized upon delivery of the product, using the residual method, assuming all the other conditions for revenue recognition have been met.  Revenue related to perpetual licenses was immaterial for all the years presented.In a limited number of arrangements with non-standard acceptance criteria, we defer the revenue until the acceptance criteria are satisfied. Reimbursements, including those related to travel and out-of-pocket expenses, are included in services and license revenue, and an equivalent amount of reimbursable expenses is included in cost of services and license revenue. In general, recurring revenue agreements are entered into for 12 to 36 months, and the professional services are performed within nine months of entering into a contract with the customer, depending on the size of integration.Our SaaS agreements provide specified service level commitments, excluding scheduled maintenance. The failure to meet this level of service availability may require us to credit qualifying customers a portion of their subscription and support fees. Based on our historical experience meeting its service level commitments, we do not currently have any liabilities on our consolidated balance sheets for these commitments.31We recognize revenue when all of the following conditions are met:        * Persuasive evidence of an arrangement exists;* Delivery has occurred or services have been rendered;* The fees are fixed or determinable; and    * Collection of the fees is reasonably assured. If we determine that any one of the four criteria is not met, we will defer recognition of revenue until all the criteria are met.Multiple-deliverable arrangements with on-demand subscription. For on-demand subscription agreements with multiple deliverables, we evaluate each element to determine whether it represents a separate unit of accounting. We determine the best estimated selling price of each deliverable in an arrangement based on a selling price hierarchy of methods contained in Finance Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") No. 2009-13, Revenue Recognition (Accounting Standards Codification ("ASC") Topic 605)-Multiple-Deliverable Revenue Arrangements. The best estimated selling price for a deliverable is based on its vendor-specific objective evidence ("VSOE"), if available, third-party evidence ("TPE"), if VSOE is not available, or estimated selling price ("ESP"), if neither VSOE nor TPE is available. Total arrangement fees are allocated to each element using the relative selling price method. We have currently established VSOE for most deliverables, except for fixed fee service arrangements and on-premise software licenses.     We considered all of the following factors to establish the ESP for fixed fee service arrangements when sold with its on-demand services: the weighted average actual sales prices of professional services sold on a stand-alone basis for on-demand services; average billing rates for fixed fee service agreements when sold with on-demand services, cost plus a reasonable mark-up and other factors such as gross margin objectives, pricing practices and growth strategy.         Multiple-deliverable arrangements with on-premise license.