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One of Erlang's real stengths is its approach to concurrent programming.[1][2] It differs from threaded programing - the more common approach - in several ways. From the programmers point-of-view, Erlang's approach is just easier to write and debug. [1] http://www.erlang.org/course/concurrent_programming.html [2] http://www.computer.org/portal/site/dsonline/menuitem.9ed3d9924aeb0dcd82 ccc6716bbe36ec/index.jsp?&pName=dso_level1&path=dsonline/2007/10&file=w5 tow.xml&xsl=article.xsl&;jsessionid=H5f2QTzQWh2zMWy36pYGytVqvVDQLjKF2mYn RhSTpwPs4qyY1JWh!1418919023 -----Original Message----- From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of Eric Lease Morgan Sent: Monday, February 18, 2008 1:43 PM To: [log in to unmask] Subject: [CODE4LIB] many processes, one result How do I write a computer program that spawns many processes but returns one result? I suppose the classic example of my query is the federated search. Get user input. Send it to many remote indexes. Wait. Combine results. Return. In this scenario when one of the remote indexes is slow things grind to a halt. I have a more modern example. Suppose I want to take advantage of many Web Services. One might be spell checker. Another might be a thesaurus. Another might be an index. Another might be a user lookup function. Given this environment, where each Web Service will return different sets of streams, how do I query each of them simultaneously and then aggregate the result? I don't want to so this sequentially. I want to fork them all at once and wait for their return before a specific time out. In Perl I can use the system command to fork a process, but I must wait for it to return. There is another Perl command allowing me to fork a process and keep going but I don't remember what it is. Neither one of these solutions seem feasible. Is the idea of threading in Java suppose to be able to address this problem? -- Eric Lease Morgan University Libraries of Notre Dame (574) 631-8604