1. An unstructured data processing apparatus, comprising: a tetrahedral annotation module for representing unstructured data generated by the apparatus using a tetrahedral data model, comprising: an annotation module for automatically creating an instance of the tetrahedral data model (“tetrahedron”) for a piece of unstructured data generated by the apparatus, wherein the tetrahedron comprises a basic attribute set, a semantic feature set, a low-level feature set, and a raw data set; a raw data module for populating the raw data set with one or more raw data files of the piece of unstructured data; a low-level feature module for populating the low-level feature set with one or more properties that are specific to a type of the piece of unstructured data; a semantic feature module for populating the semantic feature set with one or more semantic properties of the piece of unstructured data; a basic attribute module for populating the basic attribute set with one or more attributes that are universal to unstructured data; an association module for populating the tetrahedron with associations among elements of different sets; and a non-transitory computer-readable storage medium for storing the populated tetrahedron in a non-transitory computer-readable storage medium.