1.4. YANG++ Standard Library

The YANG++ standard library is a set of conceptual APIs that can be implemented in tools. There are also an XPath library function defined for each API.

1.4.1. Compare Classes

The 'compare' API allows two Class Instances to be compared.

• Only the naming information is compared

• Other child nodes of the class root are ignored for this API

Conceptual API

rpc compare {
  input {
    leaf class1-path {
      type string;  // path to class instance
      mandatory true;
    }
    leaf class2-path {
      type string;  // path to class instance
      mandatory true;
    }
  }
  output {
    leaf result {
      type enumeration {
        enum less {
          value -1;
          description "class1 is sorted before class2.";
        }
        enum equal {
          value 0;
          description "class1 sorting is equal to class2.";
        }
        enum more {
          value 1;
          description "class1 is sorted after class2.";
        }
      }
    }
  }

XPath API

Function: number compare (node-set, node-set)

Requirements:

• This function compares the class identifier for the first node-set to the second node-set.

• Each node-set is expected to represent an instance of the same class.

• If the class is based on a container then the value 0 is always returned.

• If the class is based on a list with an empty key-stmt, then the value 0 is always returned.

• If the class is based on a user-ordered list, then the behavior is not defined

• If the class is based on any other list then the key leafs must match

• All classes must support canonical identifier name representations.

• All compare operations are done on the canonical key value representations.

• All classes should support a canonical order.

• The actual canonical order may be implementation dependent, as allowed by YANG 1.1 for system-ordered lists.

Return Value:

• The value -1 is returned if the first node-set is ordered before the second node-set.

• The value 0 is returned if the first node-set order is equal to the second node-set.

• The value 1 is returned if the first node-set is ordered after the second node-set.

TBD: examples