{ "items" : [
    { "id" : "http://dbpedia.org/resource/X-wave"
      "properties" : {
        "http://www.w3.org/2000/01/rdf-schema#comment" : [ "In physics, X-waves are localized solutions of the wave equation that travel at a constant velocity in a given direction. X-waves can be sound, electromagnetic, or gravitational waves. They are built as a non-monochromatic superposition of Bessel beams.  X-waves carry infinite energy. Finite-energy realizations have been observed in various frameworks.In optics, X-waves solution have been reported within a quantum mechanical formulation." ] ,
        "http://www.w3.org/2002/07/owl#differentFrom" : [ "http://dbpedia.org/resource/X_band",
          "http://dbpedia.org/resource/X-ray"] } } }
