NODAL: Navigation & Editing

Lee Iverson
OHS Design Group

Design Strategy

Organization

• The fundamental navigation building block is a Path, which represents a kind of cursor into the document graph being examined. These Path interfaces are distinct from the data modelling interfaces, in order to mitigate the potential impact of node versioning on parent nodes. Nodes are only accessible if a user is able to construct a Path to that node. Moreover, each Path has exactly one parent Path and is thus able to represent the sibling relationships between nodes in a particular document, a concept not usually considered to be compatible with multiple node parents.
• Each navigational operation in the Path interfaces is associated with a unit of encoding in the path language. Thus any Path can automatically be encoded as an absolute path description in the path language. Moreover the results of Path difference operations can likewise be encoded as relative path descriptions in the Path language.

Paths

Cursors

interface Path {
  readonly attribute Value content;
  readonly attribute Document document;
  
  readonly attribute NodalPath parent;
  readonly attribute Path previousPath;
  readonly attribute Path nextPath;
  
  RelativePath difference (in Path path);
};

interface RelativePath : Path {
};

interface NodePath : Path {
  readonly attribute Path firstChild;
  readonly attribute Path lastChild;
  
  readonly attribute integer length;
  Path item (in integer index);
  
  Editor edit ();
};

interface NodePath : Path {
  Path property (in Name name);
};

interface SequencePath : Path {
};

interface MapPath : Path {
  Path value (in Value name);
};

Editors