Question: When did relational quantum mechanics appear?
About the article "Quantum mechanics", section "Philosophical implications".

Candidate passages:
 "This article is intended for those already familiar with quantum mechanics and its attendant interpretational difficulties.
Readers who are new to the subject may first want to read the introduction to quantum mechanics."
The relational approach to quantum physics is an alternative approach to and interpretation of quantum mechanics.
It asserts that the physical world can only be studied accurately in terms of "relationships" between systems, as all experimentally verifiable facts about the world result explicitly from interactions (such as the interaction between a light field and a detector).
According to the relational approach, the assumption that objects possess absolute properties (such as an absolute particle, independent of any detection frame) inevitably leads to ambiguities and paradoxes when these objects are studied closely.
The approach was adopted, in a time span of 1992-1996, by Q. Zheng, S. Hughes, and T. Kobayashi in the University of Tokyo.
As early as in 1985, S. Kochen suggested that the paradoxes of quantum physics could be overcome by developing a relational approach, which was needed at one time to solve the paradoxes of relativistic physics of space and time.
It is also hoped that this entry will serve as a complement to Rovelli’s relational quantum mechanics (RQM).
Historically, the theory of relativity and quantum mechanics were intertwined with each other and the compatibility between both theories was a main theme throughout the Bohr-Einstein debate.
In both theories the physicists emphasized that only measurable quantities, that is, observables, belong in a theory.
Bohr compared his approach to Einstein’s theory of relativity and asserted that in the treatment of quantum processes the complementarity of the measuring results cannot be ignored, just as in high-speed phenomena the relativity of observation cannot be neglected when the simultaneity comes into question.
But Einstein replied: “A good joke should not be repeated too often.” The debate continued in connection with Einstein-Podolsky-Rosen (EPR) paradox, and Bohr proposed the relational conception of quantum states.
Through their analysis Bohm and Schumacher concluded that the characteristic feature of this debate is the failure to communicate due to the absence of a full harmony of quantum mechanics with relativity.
Modern attempts to embrace a relational approach with interpretations of quantum mechanics have been tried many times, ranging from Everett's relative-state interpretation (Everett, 1957), sigma algebra of interactive properties (Kochen, 1979), quantum reference systems (Bene, 1992), quantum theory of the universe (Smolin, 1995), to relational quantum mechanics (Rovelli, 1996).
They more or less emphasize the relational nature of quantum states.
For more information, please refer to the further reading list. 
  Relational quantum mechanics, an interpretation of quantum mechanics which treats the state of a quantum system as being observer-dependent, "that is," the state is the relation between the observer and the system "Relation" (journal), the first newspaper Sexual relations, euphemistic term for human sexual activity  
Famous thought experiments.
Thought experiments are popular in physics and include:  Bell's spaceship paradox (special relativity)  Brownian ratchet (Richard Feynman's "perpetual motion" machine that does not violate the second law and does no work at thermal equilibrium)  Bucket argument – argues that space is absolute, not relational  Double-slit experiment (quantum mechanics)  Elitzur–Vaidman bomb-tester (quantum mechanics)  Einstein's box  EPR paradox (quantum mechanics) (forms of this have actually been performed)  Feynman sprinkler (classical mechanics)  Galileo's ship (classical relativity principle) 1632  Galileo's Leaning Tower of Pisa experiment (rebuttal of Aristotelian Gravity)  GHZ experiment (quantum mechanics)  Heisenberg's microscope (quantum mechanics)  Kepler's Dream (change of point of view as support for the Copernican hypothesis)  Ladder paradox (special relativity)  Laplace's demon  Maxwell's demon (thermodynamics) 1871  Monkey and the Hunter, The (gravitation)  Moving magnet and conductor problem  Newton's cannonball (Newton's laws of motion)  Popper's experiment (quantum mechanics)  Quantum pseudo telepathy (quantum mechanics)  Quantum suicide (quantum mechanics)  Schrödinger's cat (quantum mechanics)  Sticky bead argument (general relativity)  Renninger negative-result experiment (quantum mechanics)  Twin paradox (special relativity)  Wheeler's delayed choice experiment (quantum mechanics)  Wigner's friend (quantum mechanics)  
In physics, fractional quantum mechanics is a generalization of standard quantum mechanics, which naturally comes out when the Brownian-like quantum paths substitute with the Lévy-like ones in the Feynman path integral.
It has been discovered by Nick Laskin who coined the term "fractional quantum mechanics".  
 as a high-level approach to quantum information and computation.
Categorical quantum mechanics, when applied to quantum information theory or quantum computing, provides high-level methods for these areas.
For example, Measurement Based Quantum Computing.