This is sometimes a formidable problem since it can involve anticipating and describing the processing that is to be applied to the information in the document. The essence of the Architectural Forms idea is that it allows users to extend the attribute set for an element without doing violence to the basic processing, parsing and integrity of the DTD or associated document instances. Extending the attribute set allows users to express and preserve information that would otherwise require use of external files. Background SGML systems must couple an SGML parser with an application. As far as the parser is concerned, an SGML file is a series of nested containers.
Some containers hold data, some hold other containers and some hold both.
However, all the containers are of the same nature. SGML attributes and their values are also attached to containers and provide extra information about particular containers. From the application's point of view, containers are processed based on the information attached to them. In this kind of application, processing semantics are determined directly be the container names. The strength of SGML is realized when multiple sets of processing semantics can be attached to a single set of DTD named containers.