Viewing and editing markup language files with complex semantics

A data processing system for editing a document written in a markup language, comprising:

• a memory storing said document, a primary editor, and a plurality of specialized editors;
• a display;
• a computer processor connected to said display and said memory operative to:
• automatically define a tree of hierarchical elements of said document comprising a first layer of hierarchical elements, a second layer of hierarchical elements, and a boundary layer of hierarchical elements according to a document type definition (DTD) or schema of the document, said boundary layer being disposed between said first layer and said second layer, wherein said hierarchical elements in said boundary layer head respective subtrees comprising a portion of said second layer of hierarchical elements, said subtrees having child elements;
• edit said first layer of hierarchical elements using a tree view editor;
• establish an association of respective said specialized editors with said hierarchical elements in said boundary layer;
• responsively to said association automatically associate said specialized editors with said child elements of said subtrees, respectively;
• and
• cooperatively with said display, said computer processor presents and edits content of said hierarchical elements in said boundary layer and presents and edits content of said child elements of said subtrees thereof using said respective specialized editors, the specialized editors are from applications different from the applications of the tree view editor and primary editor.