1. A method, implemented by one or more processors in a computing system, for generating a multidimensional synopsis of a stream of textual data, the method comprising: accessing, by the one or more processors, a stream of textual data that includes a number of elements of textual data, each element of textual data comprising plain text content that is associated with an author and is directed to a particular subject; identifying, by the one or more processors, a first dimension and a second dimension for the stream of textual data, the first dimension including a number of concepts that each represent a subject attribute of the particular subject, the second dimension including a number of concepts that each represent an author attribute; processing, by the one or more processors, each of the number of elements of textual data to identify which of the concepts of the first and second dimension appear in the plain text content included in the element, and for each concept within the first dimension that appears in the plain text content included in the element, generating a quantitative value; and generating, by the one or more processors, the multidimensional synopsis of the stream of textual data by generating a score for each intersecting set of concepts from the corresponding quantitative values, each score representing a prevalence of the intersecting set of concepts within the stream of textual data.