Nothing more really needs to be said in terms of the knowledge engine construct according to Google but significant others dispute Google's claim to fame in this nascent field and with good reason.
Wolfram Research promises ready access to the pursuit of knowledge via Wolfram Alpha, a computational knowledge engine promising innumerable ways to get the correct answer to difficult questions in real time, something not even foreseen just 5 years ago. Another player in the knowledge game is Bing, Microsoft's competitor to Google. Bing uses Wolfram Research tech on the knowledge side of things. Also forgot IBM's Watson, a major player for sure.
Precursors to The Knowledge Engine - Greatly Edited
"Every one knew how laborious the usual method is of attaining to arts and sciences; whereas, by his contrivance, the most ignorant person, at a reasonable charge, and with a little bodily labour, might write books in philosophy, poetry, politics, laws, mathematics, and theology, without the least assistance from genius or study.” He then led me to the frame, about the sides, whereof all his pupils stood in ranks. It was twenty feet square, placed in the middle of the room. The superfices was composed of several bits of wood, about the bigness of a die, but some larger than others. They were all linked together by slender wires. These bits of wood were covered, on every square, with paper pasted on them; and on these papers were written all the words of their language, in their several moods, tenses, and declensions; but without any order. The professor then desired me “to observe; for he was going to set his engine at work.” The pupils, at his command, took each of them hold of an iron handle, whereof there were forty fixed round the edges of the frame; and giving them a sudden turn, the whole disposition of the words was entirely changed. He then commanded six-and-thirty of the lads, to read the several lines softly, as they appeared upon the frame; and where they found three or four words together that might make part of a sentence, they dictated to the four remaining boys, who were scribes. This work was repeated three or four times, and at every turn, the engine was so contrived, that the words shifted into new places, as the square bits of wood moved upside down." - Gulliver's Travels, Jonathan Swift