ISO/IEC JTC1/SC18/WG8 N1711 Information Described by SGML Markup ("SGML Information Set") PART I: ELEMENT STRUCTURE (INCOMPLETE) This paper is an early step toward defining a class-object model for SGML element structure. The model is presented using vocabulary defined in an accompanying paper (ISO/IEC JTC1/SC18/WG8/ N1710). It is expected that this model will be refined and elaborated over time. As of this writing, the effort is not complete. In any case, it, does not represent the only possible approach. This draft is intended to initiate discussion; later versions will actually define the element structure. Note that the model does not account for SGML syntax (the character strings used to represent a particular element structure), entity structure, or marked section structure. The model begins by identifying classes defined in ISO 8879. Some of these classes are listed in the following table, where the first column contains a name usually given to instances of the class: Class Property Rule --------------------------------------------------------------------- Attribute Name An SGML name Value A character string, or an indication that no value was specified Element Generic An SGML generic identifier identifier Attribute A set of attributes information Content A sequence of data characters, pro- cessing instructions, elements, and references to subdocument, specific character data, or external data enti- ties. No element appears more than once in the sequence of elements formed by listing the original ele- ment, the elements in its content, the elements in their content, and so on. Attribute Name An SGML name Type Declared Value An SGML declared value Content Indicates whether this is a content reference reference indicator Fixed attribute Indicates whether this is a fixed indicator attribute Fixed value Value of a fixed attribute Required Indicates whether this is a required attribute attribute indicator Class of Derived from the class of Attributes; attributes of enforces SGML rules for allowed this type values of attributes Element Type Name An SGML generic identifier Allowable Content model or declared value content Attribute A sequence of attribute types definition list Class of Derived from the class of Elements; elements of enforces SGML rules for attributes this type and content Document Type Document type An SGML generic identifier name Element types Set of element types Class of Derived from the class of Elements documents of and the value of the Element's Name this type must be the same as the document type name A document type definition defines particular element types: Class Property Rule --------------------------------------------------------------------- Instance of a Name The name exhibited by the attribute particular type attribute type (derived from attribute) Value A string interpreted according to Clause 7.9.3 of ISO 8879 that satis- fies the declared value exhibited by the attribute type Instance of a Generic The SGML generic identifier speci- particular identifier fied for this element type element type (derived from element) Attribute A set of attributes as specified in the information element type, including one for each required attribute, Content Content permitted for elements of this type, accounting for inherited exceptions. Element Generic The document type name structure identifier (instance of a document type) Attribute As for instance of a particular element information type Content As for instance of a particular element type