Instruction interfacesHuman participants have access to all process, task, and instruction data that is persisted at this stage via instruction interfaces. Instruction interfaces allow to contribute input in form of Social Computer instructions and may abstract from the raw syntax and semantics of those. We differentiate between built-in, add-on, and mediated instruction interfaces as depicted in Figure 3. Built-in instruction interfaces are a part of the Social Computer core system. Add-on instruction interfaces are remote services that allow to access tasks from a Social Computer instance and to contribute input in an alternative way. Mediated instruction interfaces do not implement the API of a Social Computer instance directly but still allow to interact with it through the means of a built-in or add-on instruction interface. The built-in instruction interfaces are: a) the push task performer, which allows to interact with human participants via Twitter and facebook; b) the Linked Data interface, which allows to access all process, task and instruction data as raw data served in conformance with the Linked Data principles \citep*{Heath_2011}.