the source code so that it can be referenced. The abstract representation of this conceptual entity, a "function argument" instance, will likely be mentioned in the function signature, and also one or more times within the implementation code body. Since the function as a whole is the parent of both its header or "signature" information as well as its implementation body, an AST would not be able to use the same node to co-identify the multiple uses or appearances of the argument entity. This is solved by the DAG nature of an ASG. A key advantage of having a single, distinct node identity for any given code element is that each element's properties are, by definition, uniquely stored. This simplifies refactoring operations, because there is exactly one existential nexus for any given property instantiation. If the developer decides to change a property value such as the "name" of any code element (the "function argument" in this example), the ASG inherently exposes that value in exactly one place, and it follows that any such property changes are implicitly, trivially, and immediately propagated globally. See also Abstract syntax tree Ontology (computer science) Semantic Web Semantic Grid References External links Graph data structures Formal languages