1. One or more computer-readable media storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising: receiving a request to execute a first application on a computing device; determining if the first application is directly executable on the computing device; executing the first application at least partly in response to determining that the first application is directly executable on the computing device; and at least partly in response to determining that the first application is not directly executable on the computing device: determining if the first application specifies an application for executing the first application; executing the specified application on the computing device at least partly in response to determining that the first application specifies an application, the specified application for executing the first application; and executing a default application on the computing device at least partly in response to determining that the first application does not specify an application, the default application for executing the first application.