Why I can't issue an asset which name is already exist? I got a error as "xcp" is already used.
It's by design.
I don't get it. As "xcp" for example, Some one has issued "xcp" already. And I have some "xcp" and want to sell it. I can't sell it if I didn't issue it, unless I use another name. Why? I mean all the same thing should be under the same name.
because BobsXCPTokens are a different thing from NxtskysXCPTokens. Just issue them like this NxtskysXCP.
Thanks, as a newbie, I don't completely understand how AE works. Is there any paper used to explain the AE works in detail? The NXT wiki is to simply too describe AE system.
ill just explain it to you right now. Exchanges like nxt, ripple, and mastercoin work with an idea called colored coins. So with a bitcoin any one bitcoin is the same as any other bitcoin. They are what we call fungible. Colored coins are intentionally not fungible. They are intentionally distinct and different from one another. Colored coins have a value attached to them. So for example, speaking in abstractions here, a colored nxt may have the value attached to it of "Nxtsky promises to pay 1 btc to who ever sends him this token, signed netsky". Now that token can be traded on a market.
Lets say betty wants to trade litecoin for bitcoin. She sends litecoin to "hanks litecoin gateway" with a message attached "bettys nxt address:blablabla". Hank will issue "X hankLTCTokens" and sends them to bettys nxt address. Betty uses these to fill the highest bid for on their orderbook thus gaining nxt. Next betty uses her nxt to fill the lowest ask on the orderbook for nxtskysXCPTokens. She sends her nxtskysXCPTokens to nxtskys nxt address with a message attached "bettys xcp address:blablabla". Betty waits for the xcp to arrive.
its obvious to most at first the disadvantages of what i just described. Its very complex compared to sending your coins to cryptsy but this is the cost of decentralization and decentralization comes with its own rewards. at some point in the future you will not just be buying any old random token. You will buy the ones issued by the guy who lives down the street so you can go there and pick them up in person.