Table of contents

Appendices

3.8 DOM Interfaces and DOM Implementations

The DOM specifies interfaces which may be used to manage XML or HTML documents. It is important to realize that these interfaces are an abstraction - much like "abstract base classes" in C++, they are a means of specifying a way to access and manipulate an application's internal representation of a document. Interfaces do not imply a particular concrete implementation. Each DOM application is free to maintain documents in any convenient representation, as long as the interfaces shown in this specification are supported. Some DOM implementations will be existing programs that use the DOM interfaces to access software written long before the DOM specification existed. Therefore, the DOM is designed to avoid implementation dependencies; in particular,

1. Attributes defined in the IDL do not imply concrete objects which must have specific data members - in the language bindings, they are translated to a pair of get()/set() functions, not to a data member. Read-only attributes have only a get() function in the language bindings.

2. DOM applications may provide additional interfaces and objects not found in this specification and still be considered DOM conformant.

3. Because we specify interfaces and not the actual objects that are to be created, the DOM cannot know what constructors to call for an implementation. In general, DOM users call the createX() methods on the Document class to create document structures, and DOM implementations create their own internal representations of these structures in their implementations of the createX() functions.

The Level 2 interfaces were extended to provide both Level 2 and Level 3 functionality.

DOM implementations in languages other than Java or ECMAScript may choose bindings that are appropriate and natural for their language and run time environment. For example, some systems may need to create a Document3 class which inherits from a Document class and contains the new methods and attributes.

DOM Level 3 does not specify multithreading mechanisms.