Meta-knowledge
Meta-knowledge or metaknowledge is knowledge about knowledge.Some authors divide meta-knowledge into orders:

zero order meta-knowledge is knowledge whose domain is not knowledge (and hence zero order meta-knowledge is not meta-knowledge per se)
first order meta-knowledge is knowledge whose domain is zero order meta-knowledge
second order meta-knowledge is knowledge whose domain is first order meta-knowledge
most generally, 
  
    
      
        n
        +
        1
      
    
    {\displaystyle n+1}
   order meta-knowledge is knowledge whose domain is 
  
    
      
        n
      
    
    {\displaystyle n}
   order meta-knowledge.Other authors call zero order meta-knowledge first order knowledge, and call first order meta-knowledge second order knowledge; meta-knowledge is also known as higher order knowledge.Meta-knowledge is a fundamental conceptual instrument in such research and scientific domains as, knowledge engineering, knowledge management, and others dealing with study and operations on knowledge, seen as a unified object/entities, abstracted from local conceptualizations and terminologies. Examples of the first-level individual meta-knowledge are methods of planning, modeling, tagging, learning and every modification of a domain knowledge. Indeed, universal meta-knowledge frameworks have to be valid for the organization of meta-levels of individual meta-knowledge. Meta-Knowledge may be automatically harvested from electronic publication archives, to reveal patterns in research, relationships between researchers and institutions  and to identify contradictory results.