tailieunhanh - Peer to Peer is the next great thing for the internet phần 6

Là đồ thị liên quan đến mạng xã hội như thế nào? Chúng ta có thể đại diện cho một mạng xã hội như một đồ thị bằng cách tạo ra một đỉnh cho mỗi cá nhân trong nhóm và thêm một cạnh giữa hai đỉnh bất cứ khi nào các cá nhân tương ứng biết nhau. | Peer to Peer Harnessing the Power of Disruptive Technologies How are graphs related to social networks We can represent a social network as a graph by creating a vertex for each individual in the group and adding an edge between two vertices whenever the corresponding individuals know one another. Each vertex will have a different number of edges connected to it going to different places depending on how wide that person s circle of acquaintances is. The resulting structure is likely to be extremely complex for example a graph for the United States would contain over 280 million vertices connected by a finely tangled web of edges. Computer networks bear a strong resemblance to social networks and can be represented by graphs in a similar way. In fact you ve probably seen such a graph already if you ve ever looked at a connectivity map for a LAN or WAN although you might not have thought of it that way. In these maps points representing individual computers or routers are equivalent to graph vertices and lines representing physical links between machines are edges. Another electronic analogue to a social network is the World Wide Web. The Web can be viewed as a graph in which web pages are vertices and hyperlinks are edges. Just as friendship links in a social network tend to connect members of the same social circle hyperlinks frequently connect web pages that share a common theme or topic. There is a slight complication because unlike friendships hyperlinks are one-way that is you can follow a hyperlink from a source page to a target page but not the reverse. For Web links properly speaking we need to use a directed graph which is a graph in which edges point from a source vertex to a target vertex rather than connecting vertices symmetrically. Directed graphs are usually represented by drawing their edges as arrows rather than lines as shown in Figure . Figure . A directed graph Most importantly for our purposes peer-to-peer networks can be regarded as .