1. A method comprising performing a machine-executed operation involving first instructions, wherein the machine-executed operation is at least one of: A) sending the instructions over transmission media; B) receiving the instructions over transmission media; C) storing the instructions onto a machine-readable storage medium; and D) executing the instructions; wherein the first instructions are instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of: storing metadata that describes the structure of a class of documents that conform to the metadata; wherein the metadata specifies a caching policy that is applicable to documents that conform to the metadata; generating a document that conforms to the metadata; wherein the document includes a reference to the metadata to which the document conforms; and serving the document to a client process.