Salesforce.com has two unequal brothers in the platform-as-a-service (PaaS) space. While force.com is the basis and natural extensibility platform for the core CRM system, the Heroku platform acquired at the end of 2010 addresses developers with open source stacks. The two of them could not be more different. Force.com is an application-centric PaaS that attracted a huge ecosystem building add-ons around Salesforce.com’s Sales, Service, and Marketing application. They all work together somehow because of the very limited freedom for developers. All apps usually start with the same canonical CRM data model, use the same data object store, use the same proprietary programing language (APEX), and use the same user interface techniques. That’s why force.com apps or add-ons fit nicely into the business buyer's perspective.