Comprehensive attribute inheritance

The ODA mechanism for inheriting layout attributes (such as placement of blocks of contents within pages and rectangular areas called frames) and presentation attributes (such as character sets and the placement of items within blocks) is not sufficient. If an attribute value is not specified for the object or its class, then the value can only be inherited according to the object’s position in the tree and not according to its class (chapter, list etc.).

Attribute inheritance can be achieved by adding a facility called “style tables” which will enable the style inherited by an object (and hence its format) to depend both on its class and is position in the document. This will be very valuable for hypertext in order to distinguish between objects of the same type that have different status (such as open and close buttons). It can also be extended to specify changes of state ( for example, when selecting a hotspot) by changing the style table.