1. In a content categorization request entity, a method for content categorization, comprising: transmitting a categorization ability negotiation request to a content categorization providing entity to request categorization abilities of the content categorization providing entity; receiving the categorization abilities of the content categorization providing entity returned by the content categorization providing entity, wherein categorization abilities of the content categorization providing entity includes one of the group consisting of: content types supported by the content categorization providing entity; content coding formats supported by the content categorization providing entity; content language types supported by the content categorization providing entity; content size types supported by the content categorization providing entity; content locators supported by the content categorization providing entity; content identifiers supported by the content categorization providing entity; content digests supported by the content categorization providing entity; digital signature algorithm types supported by the content categorization providing entity; and content categorization rules supported by the content categorization providing entity; based upon one of the categorization abilities of supported by the content categorization providing entity, transmitting a content categorization request to the content categorization providing entity; and receiving, by the content categorization request entity, a categorization result of the content returned by the content categorization providing entity.