Guideline A.3.4: (For the authoring tool user interface) Enhance navigation and editing via content structure. [Implementing A.3.4] Rationale: Some authors who have difficulty typing or operating the mouse benefit when authoring tools make use of the structure present in web content to simplify navigating and editing the content. A.3.4.1 Navigate By Structure: If editing-views expose the markup elements in the web content being edited, then the markup elements (e.g. source code, content renderings) are selectable and navigation mechanisms are provided to move the selection focus between elements. (Level AA) Implementing A.3.4.1 A.3.4.2 Navigate by Programmatic Relationships: If editing-views allow editing of programmatic relationships within web content, then mechanisms are provided that support navigation between the related content. (Level AAA) Note: Depending on the web content technology and the nature of the authoring tool, relationships may include, but are not limited to, element nesting, headings, labeling, programmatic definitions, and ID relationships. Implementing A.3.4.2