The following sections contain the formal SGML definition of HTML 4.
It includes the SGML declaration, the Document Type Definition (DTD), and the Character entity references, as well as a sample SGML catalog.
A command line system identifier of - can be used to refer to the standard input.
(Normally in a system identifier, Part of an SGML System Conforming to International Standard ISO 8879 -- Standard Generalized Markup Language.
The article is organized in four main sections plus an appendix. XML is a markup language for documents containing structured information.
Structured information contains both content (words, pictures, etc.) and some indication of what role that content plays (for example, content in a section heading has a different meaning from content in a footnote, which means something different than content in a figure caption or content in a database table, etc.). A markup language is a mechanism to identify structures in a document.
Not all ESIS information is output in this case: the active LPDs are not explicitly reported, although each link attribute is qualified with its link type name; there is no information about result elements; when there are multiple link rules applicable to the current element, onsgmls always chooses the first.These files are also available in ASCII format as listed below: Many authors rely on a limited set of browsers to check on the documents they produce, assuming that if the browsers can render their documents they are valid.Unfortunately, this is a very ineffective means of verifying a document's validity precisely because browsers are designed to cope with invalid documents by rendering them as well as they can to avoid frustrating users.specified on the command line separately, rather than concatenating them. If -tfilename is also specified, then the specified filename will be prefixed to the sysid to make the filename for the RAST result for each sysid.Map public identifiers and entity names to system identifiers using the catalog entry file whose system identifier is sysid. If there is a catalog entry file called catalog in the same place as the document entity, it will be searched for immediately after those specified by -c.This release is both a bug fix release and also contains the early XML Schemas structures and datatypes code, beware, all interfaces are likely to change, there is huge holes, it is clearly a work in progress and don't even think of putting this code in a production system, it's actually not compiled in by default.October 3, 1998 Norman Walsh Author's Note: It is somewhat remarkable to think that this article, which appeared initially in the Winter 1997 edition of the World Wide Web Journal was out of date by the time the final XML Recommendation was approved in February.Otherwise you can use the following sample SGML catalog.It assumes that the DTD has been saved as the file "strict.dtd" and that the entities are in the files "HTMLlat1.ent", "HTMLsymbol.ent" and "HTMLspecial.ent".For better validation, you should check your document against an SGML parser such as nsgmls (see [SP]), to verify that HTML documents conform to the HTML 4 DTD.If the document type declaration of your document includes a URI and your SGML parser supports this type of system identifier, it will get the DTD directly.