ASPs: The Integration Challenge LEN TAKEUCHI, SALESCENTRIX The promise of software as a service is becoming a reality with many ASPs (application service providers). Organizations using ASPs and third-party vendors that provide value-added products to ASPs need to integrate with them. ASPs enable this integration by providing Web service-based APIs. There are significant differences between integrating with ASPs over the Internet and integrating with a local application. When integrating with ASPs, users have to consider a number of issues, including latency, unavailability, upgrades, performance, load limiting, and lack of transaction support. Web Service API The integration APIs provided by ASPs are usually based on Web services. The ASPs provide documentation and WSDL (Web Services Description Language) files for the APIs. The user of the API uses the WSDL files to generate the Web service client using a Web service toolkit (e.g., Apache Axis). An ASP may provide a feature in its software to create custom fields for various entities. For example, CRM (customer relationship management) systems are likely to provide custom fields on such entities as customer accounts, since organizations will have specific information they want to track about a customer. If an ASP supports custom fields, it will usually provide two separate WSDL files: one generated specifically for an organization based on the custom fields defined by that organization, and one that is generic.