1. An unstructured data processing apparatus, comprising: a processor; and a non-transitory computer-readable storage medium for storing a tetrahedral data model in the non-transitory computer-readable storage medium; and a tetrahedral annotation module for representing unstructured data generated by the apparatus using the tetrahedral data model, the tetrahedral annotation module comprising: an annotation module for automatically creating an instance of the tetrahedral data model for a piece of unstructured data generated by the apparatus, the tetrahedral data model having a vertex, four facets, and lines between the facets, the vertex including an identifier associated with the tetrahedral data model, the four facets of the tetrahedral data model including a basic attribute set, a semantic feature set, a low-level feature set, and a raw data set, and the lines between the facets designating associations among the basic attribute set, the semantic feature set, the low-level feature set, and the 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, the low-level feature set including one or more of color, texture, shape for an image, audio frequency for audio, or a key frame for a video; a semantic feature module for populating the semantic feature set with one or more semantic properties of the piece of unstructured data, the semantic feature set including one or more of author intention, subject, descriptions of content of the unstructured data, descriptions of objects of the unstructured data, meaning of one or more of the low-level features, annotations in keywords, free text styles, or concepts of data objects described using ontology; a basic attribute module for populating the basic attribute set with one or more attributes that are universal to unstructured data, the basic attribute set including one or more of a name, type, author, or time of creation; and an association module for populating the tetrahedral data model with the lines designating associations among the basic attribute set, the semantic feature set, the low-level feature set, and the raw data set.