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A peer-to-peer system of nodes without central infrastructure.

Centralized server-based service model (not peer-to-peer).

Peer-to-peer (abbreviated to P2P) refers to a computer network in which each computer in the network can act as a client or server for the other computers in the network, allowing shared access to files and peripherals without the need for a central server. P2P networks can be set up in the home, a business or over the Internet. Each network type requires all computers in the network to use the same or a compatible program to connect to each other and access files and other resources found on the other computer. P2P networks can be used for sharing content such as audio, video, data or anything in digital format.

P2P is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged participants in the application. Each computer in the network is referred to as a node. The owner of each computer on a P2P network would set aside a portion of its resources - such as processing power, disk storage or network bandwidth -to be made directly available to other network participant, without the need for central coordination by servers or stable hosts.^[1] With this model, peers are both suppliers and consumers of resources, in contrast to the traditional client–server model where only servers supply (send), and clients consume (receive).

The first peer-to-peer application was the file sharing system Napster, originally released in 1999. The concept has inspired new structures and philosophies in many areas of human interaction. Peer-to-peer networking is not restricted to technology; it also covers social processes with a peer-to-peer dynamic. In such context, social peer-to-peer processes are currently emerging throughout society.

Architecture of P2P systems[link]

Peer-to-peer systems often implement an abstract overlay network, built at Application Layer, on top of the native or physical network topology. Such overlays are used for indexing and peer discovery and make the P2P system independent from the physical network topology. Content is typically exchanged directly over the underlying Internet Protocol (IP) network. Anonymous peer-to-peer systems are an exception, and implement extra routing layers to obscure the identity of the source or destination of queries.

In structured peer-to-peer networks, peers (and, sometimes, resources) are organized following specific criteria and algorithms, which lead to overlays with specific topologies and properties. They typically use distributed hash table-based (DHT) indexing, such as in the Chord system (MIT).^[2]

Unstructured peer-to-peer networks do not impose any structure on the overlay networks. Peers in these networks connect in an ad-hoc fashion.^[3] Ideally, unstructured P2P systems would have absolutely no centralized system, but in practice there are several types of unstructured systems with various degrees of centralization. Three categories can easily be seen.

• In pure peer-to-peer systems the entire network consists solely of equipotent peers. There is only one routing layer, as there are no preferred nodes with any special infrastructure function.
• Hybrid peer-to-peer systems allow such infrastructure nodes to exist, often called supernodes.^[4]
• In centralized peer-to-peer systems, a central server is used for indexing functions and to bootstrap the entire system. Although this has similarities with a structured architecture, the connections between peers are not determined by any algorithm.

The first prominent and popular peer-to-peer file sharing system, Napster, was an example of the centralized model.^[5] Freenet and early implementations of the gnutella protocol, on the other hand, are examples of the decentralized model. Modern gnutella implementations, Gnutella2, as well as the now deprecated Kazaa network are examples of the hybrid model.

A pure P2P network does not have the notion of clients or servers but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network. This model of network arrangement differs from the client–server model where communication is usually to and from a central server. A typical example of a file transfer that does not use the P2P model is the File Transfer Protocol (FTP) service in which the client and server programs are distinct: the clients initiate the transfer, and the servers satisfy these requests.

The P2P overlay network consists of all the participating peers as network nodes. There are links between any two nodes that know each other: i.e. if a participating peer knows the location of another peer in the P2P network, then there is a directed edge from the former node to the latter in the overlay network. Based on how the nodes in the overlay network are linked to each other, we can classify the P2P networks as unstructured or structured.

Structured systems[link]

Structured P2P networks employ a globally consistent protocol to ensure that any node can efficiently route a search to some peer that has the desired file, even if the file is extremely rare. Such a guarantee necessitates a more structured pattern of overlay links. By far the most common type of structured P2P network is the distributed hash table (DHT), in which a variant of consistent hashing is used to assign ownership of each file to a particular peer, in a way analogous to a traditional hash table's assignment of each key to a particular array slot. Though the term DHT is commonly used to refer to the structured overlay, in practice, DHT is a data structure implemented on top of a structured overlay.^[6]

Distributed hash tables[link]

Distributed hash tables

Distributed hash tables (DHTs) are a class of decentralized distributed systems that provide a lookup service similar to a hash table: (key, value) pairs are stored in the DHT, and any participating node can efficiently retrieve the value associated with a given key. Responsibility for maintaining the mapping from keys to values is distributed among the nodes, in such a way that a change in the set of participants causes a minimal amount of disruption. This allows DHTs to scale to extremely large numbers of nodes and to handle continual node arrivals, departures, and failures.

DHTs form an infrastructure that can be used to build peer-to-peer networks. Notable distributed networks that use DHTs include BitTorrent's distributed tracker, the Kad network, the Storm botnet, YaCy, and the Coral Content Distribution Network.

Some prominent research projects include the Chord project, the PAST storage utility, the P-Grid, a self-organized and emerging overlay network and the CoopNet content distribution system (see below for external links related to these projects).

DHT-based networks have been widely utilized for accomplishing efficient resource discovery^[7][8] for grid computing systems, as it aids in resource management and scheduling of applications. Resource discovery activity involves searching for the appropriate resource types that match the user’s application requirements. Recent advances in the domain of decentralized resource discovery have been based on extending the existing DHTs with the capability of multi-dimensional data organization and query routing. Majority of the efforts have looked at embedding spatial database indices such as the Space Filling Curves (SFCs) including the Hilbert curves, Z-curves, k-d tree, MX-CIF Quad tree and R*-tree for managing, routing, and indexing of complex Grid resource query objects over DHT networks. Spatial indices are well suited for handling the complexity of Grid resource queries. Although some spatial indices can have issues as regards to routing load-balance in case of a skewed data set, all the spatial indices are more scalable in terms of the number of hops traversed and messages generated while searching and routing Grid resource queries. More recent evaluation of P2P resource discovery solutions under real-workloads have pointed out several issues in DHT-based solutions such as high cost of advertising/discovering resources and static and dynamic load imbalance.^[9]

Unstructured systems[link]

An unstructured P2P network is formed when the overlay links are established arbitrarily. Such networks can be easily constructed as a new peer that wants to join the network can copy existing links of another node and then form its own links over time. In an unstructured P2P network, if a peer wants to find a desired piece of data in the network, the query has to be flooded through the network to find as many peers as possible that share the data. The main disadvantage with such networks is that the queries may not always be resolved. Popular content is likely to be available at several peers and any peer searching for it is likely to find the same thing. But if a peer is looking for rare data shared by only a few other peers, then it is highly unlikely that search will be successful. Since there is no correlation between a peer and the content managed by it, there is no guarantee that flooding will find a peer that has the desired data. Flooding also causes a high amount of signaling traffic in the network and hence such networks typically have very poor search efficiency. Many of the popular P2P networks are unstructured.

In pure P2P networks: Peers act as equals, merging the roles of clients and server. In such networks, there is no central server managing the network, neither is there a central router. Some examples of pure P2P Application Layer networks designed for peer-to-peer file sharing are gnutella (pre v0.4) and Freenet.

There also exist hybrid P2P systems, which distribute their clients into two groups: client nodes and overlay nodes. Typically, each client is able to act according to the momentary need of the network and can become part of the respective overlay network used to coordinate the P2P structure. This division between normal and 'better' nodes is done in order to address the scaling problems on early pure P2P networks. As examples for such networks can be named modern implementations of gnutella (after v0.4) and Gnutella2.

Another type of hybrid P2P network are networks using on the one hand central server(s) or bootstrapping mechanisms, on the other hand P2P for their data transfers. These networks are in general called 'centralized networks' because of their lack of ability to work without their central server(s). An example for such a network is the eDonkey network (often also called eD2k).

Indexing and resource discovery[link]

Older peer-to-peer networks duplicate resources across each node in the network configured to carry that type of information. This allows local searching, but requires much traffic.

Modern networks use central coordinating servers and directed search requests. Central servers are typically used for listing potential peers (Tor), coordinating their activities (Folding@home), and searching (Napster, eMule). Decentralized searching was first done by flooding search requests out across peers. More efficient directed search strategies, including supernodes and distributed hash tables, are now used.

Peer-to-peer-like systems[link]

In modern definitions of peer-to-peer technology, the term implies the general architectural concepts outlined in this article. However, the basic concept of peer-to-peer computing was envisioned in earlier software systems and networking discussions, reaching back to principles stated in the first Request for Comments, RFC 1.^[10]

A distributed messaging system that is often likened as an early peer-to-peer architecture is the USENET network news system that is in principle a client–server model from the user or client perspective, when they read or post news articles. However, news servers communicate with one another as peers to propagate Usenet news articles over the entire group of network servers. The same consideration applies to SMTP email in the sense that the core email relaying network of Mail transfer agents has a peer-to-peer character, while the periphery of e-mail clients and their direct connections is strictly a client–server relationship. Tim Berners-Lee's vision for the World Wide Web, as evidenced by his WorldWideWeb editor/browser, was close to a peer-to-peer design in that it assumed each user of the web would be an active editor and contributor creating and linking content to form an interlinked web of links. This contrasts to the broadcasting-like structure of the web as it has developed over the years.

Advantages and weaknesses[link]

In P2P networks, clients provide resources, which may include bandwidth, storage space, and computing power. This property is one of the major advantages of using P2P networks because it makes the setup and running costs very small for the original content distributor. As nodes arrive and demand on the system increases, the total capacity of the system also increases, and the likelihood of failure decreases. If one peer on the network fails to function properly, the whole network is not compromised or damaged. In contrast, in a typical client–server architecture, clients share only their demands with the system, but not their resources. In this case, as more clients join the system, fewer resources are available to serve each client, and if the central server fails, the entire network is taken down. The decentralized nature of P2P networks increases robustness because it removes the single point of failure that can be inherent in a client-server based system.^[11]

Another important property of peer-to-peer systems is the lack of a system administrator. This leads to a network that is easier and faster to setup and keep running because a full staff is not required to ensure efficiency and stability. Decentralized networks introduce new security issues because they are designed so that each user is responsible for controlling their data and resources. Peer-to-peer networks, along with almost all network systems, are vulnerable to unsecure and unsigned codes that may allow remote access to files on a victim's computer or even compromise the entire network. A user may encounter harmful data by downloading a file that was originally uploaded as a virus disguised in an .exe, .mp3, .avi, or any other filetype. This type of security issue is due to the lack of an administrator that maintains the list of files being distributed.

Harmful data can also be distributed on P2P networks by modifying files that are already being distributed on the network. This type of security breach is created by the fact that users are connecting to untrusted sources, as opposed to a maintained server. In the past this has happened to the FastTrack network when the RIAA managed to introduce faked chunks into downloads and downloaded files (mostly MP3 files). Files infected with the RIAA virus were unusable afterwards or even contained malicious code. The RIAA is also known to have uploaded fake music and movies to P2P networks in order to deter illegal file sharing.^[12] Consequently, the P2P networks of today have seen an enormous increase of their security and file verification mechanisms. Modern hashing, chunk verification and different encryption methods have made most networks resistant to almost any type of attack, even when major parts of the respective network have been replaced by faked or nonfunctional hosts.

There are both advantages and disadvantages in P2P networks related to the topic of data backup, recovery, and availability. In a centralized network, the system administrators are the only forces controlling the availability of files being shared. If the administrators decide to no longer distribute a file, they simply have to remove it from their servers, and it will no longer be available to users. Along with leaving the users powerless in deciding what is distributed throughout the community, this makes the entire system vulnerable to threats and requests from the government and other large forces. For example, YouTube has been pressured by the RIAA, MPAA, and entertainment industry to filter out copyrighted content. Although server-client networks are able to monitor and manage content availability, they can have more stability in the availability of the content they choose to host. A client should not have trouble accessing obscure content that is being shared on a stable centralized network. P2P networks, however, are more unreliable in sharing unpopular files because sharing files in a P2P network requires that at least one node in the network has the requested data, and that node must be able to connect to the node requesting the data. This requirement is occasionally hard to meet because users may delete or stop sharing data at any point.

In this sense, the community of users in a P2P network is completely responsible for deciding what content is available. Unpopular files will eventually disappear and become unavailable as more people stop sharing them. Popular files, however, will be highly and easily distributed. Popular files on a P2P network actually have more stability and availability than files on central networks. In a centralized network, only the loss of connection between the clients and server is simple enough to cause a failure, but in P2P networks, the connections between every node must be lost in order to fail to share data. In a centralized system, the administrators are responsible for all data recovery and backups, while in P2P systems, each node requires its own backup system. Because of the lack of central authority in P2P networks, forces such as the recording industry, RIAA, MPAA, and the government are unable to delete or stop the sharing of content on P2P systems.

Social and economic impact[link]

The concept of P2P is increasingly evolving to an expanded usage as the relational dynamic active in distributed networks, i.e., not just computer to computer, but human to human. Yochai Benkler has coined the term commons-based peer production to denote collaborative projects such as free and open source software and Wikipedia. Associated with peer production are the concepts of:

• peer governance (referring to the manner in which peer production projects are managed)
• peer property (referring to the new type of licenses which recognize individual authorship but not exclusive property rights, such as the GNU General Public License and the Creative Commons licenses)
• peer distribution (or the manner in which products, particularly peer-produced products, are distributed)

Some researchers have explored the benefits of enabling virtual communities to self-organize and introduce incentives for resource sharing and cooperation, arguing that the social aspect missing from today's peer-to-peer systems should be seen both as a goal and a means for self-organized virtual communities to be built and fostered.^[13] Ongoing research efforts for designing effective incentive mechanisms in P2P systems, based on principles from game theory are beginning to take on a more psychological and information-processing direction.

Applications[link]

There are numerous applications of peer-to-peer networks. The most commonly known is for content distribution

Content delivery[link]

• Many file sharing networks, such as gnutella, G2 and the eDonkey network popularized peer-to-peer technologies. From 2004 on, such networks form the largest contributor of network traffic on the Internet.
• Peer-to-peer content delivery networks (P2P-CDN). See : Giraffic, Kontiki, Ignite, RedSwoosh.
• Peer-to-peer content services, e.g. caches for improved performance such as Correli Caches^[14]
• Software publication and distribution (Linux, several games); via file sharing networks.
• Streaming media. P2PTV and PDTP. Applications include TVUPlayer, Joost, CoolStreaming, Cybersky-TV, PPLive, LiveStation, Giraffic and Didiom.
• Spotify uses a peer-to-peer network along with streaming servers to stream music to its desktop music player.
• Peercasting for multicasting streams. See PeerCast, IceShare, FreeCast, Rawflow
• Pennsylvania State University, MIT and Simon Fraser University are carrying on a project called LionShare designed for facilitating file sharing among educational institutions globally.
• Osiris (Serverless Portal System) allows its users to create anonymous and autonomous web portals distributed via P2P network.

Exchange of physical goods, services, or space[link]

• Peer-to-peer renting web platforms enable people to find and reserve goods, services, or space on the virtual platform, but carry out the actual P2P transaction in the physical world (for example: emailing a local footwear vendor to reserve for you that comfy pair of slippers which you've always had your eyes on, or contacting a neighbor who has listed their weedwacker for rent).

Networking[link]

• Dalesa a peer-to-peer web cache for LANs (based on IP multicasting).
• Voice Peering Fabric is a peer-to-peer interconnect system for routing VoIP traffic between organizations by utilizing BGP and ENUM technology.

Science[link]

• In bioinformatics, drug candidate identification. The first such program was begun in 2001 the Centre for Computational Drug Discovery at the University of Oxford in cooperation with the National Foundation for Cancer Research. There are now several similar programs running under the United Devices Cancer Research Project.
• The sciencenet P2P search engine.

Search[link]

• Distributed search engine, a search engine where there is no central server
• YaCy, a free distributed search engine, built on principles of peer-to-peer networks.
• FAROO, a Peer-to-peer Web search engine

Communications networks[link]

• Skype, one of the most widely used internet phone applications is using P2P technology.
• VoIP (using application layer protocols such as SIP)
• Instant messaging and online chat
• Completely decentralized networks of peers: Usenet (1979) and WWIVnet (1987).

General[link]

• Research like the Chord project, the PAST storage utility, the P-Grid, and the CoopNet content distribution system.
• JXTA, for Peer applications. See Collanos Workplace (Teamwork software), Sixearch

Miscellaneous[link]

• The U.S. Department of Defense has started research on P2P networks as part of its modern network warfare strategy.^[15] In May, 2003 Dr. Tether. Director of Defense Advanced Research Project Agency testified that U.S. Military is using P2P networks.
• Kato et al.’s studies indicate over 200 companies with approximately $400 million USD are investing in P2P network. Besides File Sharing, companies are also interested in Distributing Computing, Content Distribution.
• Wireless community network, Netsukuku
• An earlier generation of peer-to-peer systems were called "metacomputing" or were classed as "middleware". These include: Legion, Globus
• Bitcoin is a peer-to-peer based digital currency.

Historical perspective[link]

Tim Berners-Lee's vision for the World Wide Web was close to a P2P network in that it assumed each user of the web would be an active editor and contributor, creating and linking content to form an interlinked "web" of links.^[16] This contrasts to the current broadcasting-like structure of the web.

Some networks and channels such as Napster, OpenNAP and IRC serving channels use a client–server structure for some tasks (e.g., searching) and a P2P structure for others. Networks such as gnutella or Freenet use a P2P structure for nearly all tasks, with the exception of finding peers to connect to when first setting up.

P2P architecture embodies one of the key technical concepts of the Internet, described in the first Internet Request for Comments, RFC 1, "Host Software" dated April 7, 1969. More recently, the concept has achieved recognition in the general public in the context of the absence of central indexing servers in architectures used for exchanging multimedia files.

Network neutrality controversy[link]

Peer-to-peer applications present one of the core issues in the network neutrality controversy. Internet service providers (ISPs) have been known to throttle P2P file-sharing traffic due to its high-bandwidth usage.^[17] Compared to Web browsing, e-mail or many other uses of the internet, where data is only transferred in short intervals and relative small quantities, P2P file-sharing often consists of relatively heavy bandwidth usage due to ongoing file transfers and swarm/network coordination packets. In October 2007, Comcast, one of the largest broadband Internet providers in the USA, started blocking P2P applications such as BitTorrent. Their rationale was that P2P is mostly used to share illegal content, and their infrastructure is not designed for continuous, high-bandwidth traffic. Critics point out that P2P networking has legitimate uses, and that this is another way that large providers are trying to control use and content on the Internet, and direct people towards a client-server-based application architecture. The client-server model provides financial barriers-to-entry to small publishers and individuals, and can be less efficient for sharing large files. As a reaction to this bandwidth throttling, several P2P applications started implementing protocol obfuscation, such as the BitTorrent protocol encryption. Techniques for achieving "protocol obfuscation" involves removing otherwise easily identifiable properties of protocols, such as deterministic byte sequences and packet sizes, by making the data look as if it were random.^[18] The ISP's solution to the high bandwidth is P2P caching, where a ISP stores the part of files most accessed by P2P clients in order to save access to the Internet.

See also[link]

• Client–server model
• Decentralized computing
• Friend-to-friend
• List of P2P protocols
• Peercasting
• Segmented downloading
• Semantic P2P networks
• Wireless ad-hoc network
• USB dead drop

References[link]

External links[link]

Wikimedia Commons has media related to: Peer-to-peer software

Edvard Grieg (1876)

Edvard Grieg (1891)
portrait by Eilif Peterssen

Edvard Grieg and Nina Hagerup. (1899)

Edvard Hagerup Grieg /ˈɛdʋɑɖ ˈhɑːgəɾʉːp gɾiːg/ (15 June 1843 – 4 September 1907) was a Norwegian composer and pianist. He is best known for his Piano Concerto in A minor, for his incidental music to Henrik Ibsen's play Peer Gynt (which includes Morning Mood and In the Hall of the Mountain King), and for his collection of piano miniatures Lyric Pieces.^[1]

Biography[link]

Edvard Hagerup Grieg was born in Bergen, Norway on 15 June 1843. His parents were Alexander Grieg (1806–1875), a merchant and vice consul in Bergen, and Gesine Judithe Hagerup (1814–1875), a music teacher and daughter of Edvard Hagerup.^[2][3] The family name, originally spelled Greig, has Scottish origins. After the Battle of Culloden in 1746, Grieg's great-grandfather traveled widely, settling in Norway about 1770, and establishing business interests in Bergen.

Edvard Grieg was raised in a musical area. His mother was his first piano teacher and taught him to play at the age of 6. Grieg studied in several schools,^{[clarification needed]} including Tank's School.^[4] He often brought in samples of his music to class.^{[citation needed]}

In the summer of 1858, Grieg met the eminent Norwegian violinist Ole Bull,^[5] who was a family friend; Bull's brother was married to Grieg's aunt.^[6] Bull recognized the 15-year-old boy's talent and persuaded his parents to send him to the Leipzig Conservatory,^[5] then directed by Ignaz Moscheles.^{[citation needed]}

Grieg enrolled in the conservatory, concentrating on the piano, and enjoyed the many concerts and recitals given in Leipzig. He disliked the discipline of the conservatory course of study, but he achieved very good grades in most areas. An exception was the organ, which was mandatory for piano students. In the spring of 1860, he survived a life-threatening lung disease. The following year he made his debut as a concert pianist, in Karlshamn, Sweden. In 1862, he finished his studies in Leipzig and held his first concert in his home town, where his programme included Beethoven's Pathétique sonata. (Grieg's own recording of his Piano Sonata, made late in his life, confirms that he was an excellent pianist).

In 1863, Grieg went to Copenhagen, Denmark, and stayed there for three years. He met the Danish composers J. P. E. Hartmann and Niels Gade. He also met his fellow Norwegian composer Rikard Nordraak (composer of the Norwegian national anthem), who became a good friend and source of great inspiration. Nordraak died in 1866, and Grieg composed a funeral march in his honor.

On 11 June 1867, Grieg married his first cousin, Nina Hagerup. The next year, their only child, Alexandra, was born. She died in 1869 from meningitis. In the summer of 1868, Grieg wrote his Piano Concerto in A minor while on holiday in Denmark. Edmund Neupert gave the concerto its premiere performance on 3 April 1869 in the Casino Theater in Copenhagen. Grieg himself was unable to be there due to conducting commitments in Christiania (as Oslo was then named). ^[7]

In 1868, Franz Liszt, who had not yet met Grieg, wrote a testimonial for him to the Norwegian Ministry of Education, which led to Grieg's obtaining a travel grant. The two men met in Rome in 1870. On Grieg's first visit, they went over Grieg's Violin Sonata No. 1, which pleased Liszt greatly. On his second visit, in April, Grieg brought with him the manuscript of his Piano Concerto, which Liszt proceeded to sightread (including the orchestral arrangement). Liszt's rendition greatly impressed his audience, although Grieg gently pointed out to him that he played the first movement too quickly. Liszt also gave Grieg some advice on orchestration, (for example, to give the melody of the second theme in the first movement to a solo trumpet).

In 1874–76, Grieg composed incidental music for the premiere of Henrik Ibsen's play Peer Gynt, at the request of the author. Many of the pieces from this work became very popular in the orchestral suites or piano and piano-duet arrangements.

Grieg had close ties with the Bergen Philharmonic Orchestra (Harmonien), and later became Music Director of the orchestra from 1880–1882. In 1888, Grieg met Tchaikovsky in Leipzig. Grieg was struck by the sadness in Tchaikovsky.^[8] Tchaikovsky thought very highly of Grieg's music, praising its beauty, originality and warmth.^[9]

Later years[link]

Edvard Grieg Museum Troldhaugen

Grieg's later life brought him fame. The Norwegian government awarded him a pension. In the spring 1903, Grieg made nine 78-rpm gramophone recordings of his piano music in Paris; all of these historic discs have been reissued on both LPs and CDs and, despite limited fidelity, show his artistry as a pianist. Grieg also made live-recording player piano music rolls for the Welte-Mignon reproducing system, all of which survive today and can be heard.

In 1906, he met the composer and pianist Percy Grainger in London. Grainger was a great admirer of Grieg's music and a strong empathy was quickly established. In a 1907 interview, Grieg stated: “I have written Norwegian Peasant Dances that no one in my country can play, and here comes this Australian who plays them as they ought to be played! He is a genius that we Scandinavians cannot do other than love.”^[10]

Edvard Grieg died in the autumn of 1907, aged 64, after a long period of illness. His final words were "Well, if it must be so." The funeral drew between 30,000 and 40,000 people out on the streets of his home town to honor him. Following his wish, his own Funeral March in Memory of Rikard Nordraak was played in an orchestration by his friend Johan Halvorsen, who had married Grieg's niece. In addition, the Funeral March movement from Chopin's Piano Sonata No. 2 was played. His and his wife's ashes are entombed in a mountain crypt near his house, Troldhaugen.

Music[link]

Grieg is renowned as a nationalist composer, drawing inspiration from Norwegian folk music. Early works include a symphony (which he later suppressed) and a piano sonata. He also wrote three sonatas for violin and piano and a cello sonata.^[2] His many short pieces for piano – often based on Norwegian folk tunes and dances – led some to call him the "Chopin of the North".^{[who?][citation needed]}

Concerto in A minor: 1. Allegro molto moderato Performed by the University of Washington Symphony, conducted by Peter Erős (Neal O'Doan, piano) Concerto in A minor: 1. Allegro molto moderato Performed by the Skidmore College Orchestra (courtesy of Musopen) Concerto in A minor: 2. Adagio Performed by the University of Washington Symphony, conducted by Peter Erős (Neal O'Doan, piano) Concerto in A minor: 2. Adagio Performed by the Skidmore College Orchestra (courtesy of Musopen) Concerto in A minor: 3. Allegro moderato molto e marcato Performed by the University of Washington Symphony, conducted by Peter Erős (Neal O'Doan, piano) Concerto in A minor: 3. Allegro moderato molto e marcato Performed by the Skidmore College Orchestra (courtesy of Musopen) Notturno, Op. 54, No. 4 Performed live by Mark Gasser Grieg plays his butterfly. Recorded 1906 Grieg plays his Wedding day. Recorded 1903

Problems listening to these files? See media help.

The Piano Concerto is his most popular work. Its champions have included the pianist and composer Percy Grainger, a personal friend of Grieg who played the concerto frequently during his long career. An arrangement of part of the work made an iconic television comedy appearance in the Christmas 1971 Morecambe and Wise Show, conducted by André Previn.

Some of the Lyric Pieces (for piano) are also well-known, as is the incidental music to Henrik Ibsen's play Peer Gynt, a play that Grieg found to be an arduous work to score properly. In a 1874 letter to his friend Frants Beyer, Grieg expressed his unhappiness with what is now considered one of his most popular compositions from Peer Gynt, In the Hall of the Mountain King: "I have also written something for the scene in the hall of the mountain King – something that I literally can't bear listening to because it absolutely reeks of cow-pies, exaggerated Norwegian nationalism, and trollish self-satisfaction! But I have a hunch that the irony will be discernible."^[11]

Grieg's popular Holberg Suite was originally written for the piano, and later arranged by the composer for string orchestra. Grieg wrote songs, in which he set lyrics by poets Heinrich Heine, Johann Wolfgang von Goethe, Henrik Ibsen, Hans Christian Andersen, Rudyard Kipling and others. Russian composer Nikolai Myaskovsky used a theme by Grieg for the variations with which he closed his Third String Quartet. Norwegian pianist Eva Knardahl recorded the composer's complete piano music during 1978 and 1980. The recordings were reissued in 2006 on 12 compact discs by BIS Records.

List of selected works[link]

• Piano Sonata in E minor, Op. 7
• Violin Sonata No. 1 in F major, Op. 8
• Concert Overture In Autumn, Op. 11
• Violin Sonata No. 2 in G major, Op. 13
• Piano Concerto in A minor, Op. 16
• Incidental music to Bjørnstjerne Bjørnson's play Sigurd Jorsalfar, Op. 22
• Incidental music to Henrik Ibsen's play Peer Gynt, Op. 23
• Ballade in the Form of Variations on a Norwegian Folk Song in G minor, Op. 24
• String Quartet in G minor, Op. 27
• Album for Male Chorus, Op. 30
• Two Elegiac Melodies for Strings, Op. 34
• Four Norwegian Dances for piano four hands, Op. 35 (later orchestrated)
• Cello Sonata in A minor, Op. 36
• Holberg Suite for piano, later arr. for string orchestra, Op. 40
• Violin Sonata No. 3 in C minor, Op. 45
• Peer Gynt Suite No. 1, Op. 46
• Lyric Suite for orchestra, Op. 54 (orchestration of four Lyric Pieces)
• Peer Gynt Suite No. 2, Op. 55
• Suite from Sigurd Jorsalfar, Op. 56
• Four Symphonic Dances for piano, later arr. for orchestra, Op. 64
• Haugtussa Song Cycle after Arne Garborg, Op. 67
• Slåtter (Peasant Dances) for piano, Op. 72
• Sixty-six Lyric Pieces for piano in ten books, Opp. 12, 38, 43, 47, 54, 57, 62, 65, 68 and 71, including: Arietta, To the Spring, Little Bird, Butterfly, Notturno, Wedding Day at Troldhaugen, At Your Feet, Longing For Home, March of the Dwarfs, Poème érotique and Gone.

See also[link]

Biography portal

• Grieg's music in popular culture
• Song of Norway the operetta.

References[link]

Notes

Bibliography

• Benestad, Finn; Schjelderup-Ebbe, Dag (1990) [1980] (in Norwegian). Edvard Grieg – mennesket og kunstneren (2 ed.). Oslo: Aschehoug. ISBN 82-03-16373-4. 

Further reading[link]

English[link]

• Grieg The Writer ed. by Bjarne Kortsen. Vol I: Essays and Articles, vol II: Letters to Frants Beyer (editio norvegica, Bergen/Norway 1972)
• Edvard Grieg in England by Lionel Carley (The Boydell Press 2006) ISBN 1-84383-207-0
• Grieg: Music, Landscape and Norwegian Cultural Identity by Daniel Grimley (The Boydell Press 2006) ISBN 1-84383-210-0
• Songs of Edvard Grieg by Beryl Foster (The Boydell Press new edition 2007) ISBN 1-84383-343-3
• Edvard Grieg by Henry Theophilius Finck (Bastian Books new edition 2008) ISBN 978-0-554-96326-6
• Grieg by John Horton (London 1950)

Norwegian[link]

• Benestad, Finn/Schjelderup-Ebbe, Dag (2007): Edvard Grieg – mennesket og kunstneren. H. Aschehoug & Co. (W. Nygaard), Oslo. ISBN 978-82-03-23459-0
• Bredal, Dag/Strøm-Olsen, Terje (1992): Edvard Grieg – Musikken er en kampplass. Aventura Forlag A/S, Oslo. ISBN 82-588-0890-7
• Johansen, David Monrad (1956): Edvard Grieg. Gyldendal Norsk Forlag, Oslo.
• Bøe, Finn (1949): Trekk av Edvard Griegs personlighet. Oslo.

External links[link]

Wikimedia Commons has media related to: Edvard Grieg

• Grieg 2007. Official Site for 100th year commemoration of Edvard Grieg
• The Grieg archives at Bergen Public Library
• Troldhaugen Museum, Grieg's home
• Biography of Grieg by prof. Harald Herresthal
• Works by Edvard Grieg on Open Library at the Internet Archive
• Edvard Grieg statue by Sigvald Asbjornsen Prospect Park (Brooklyn)
• Films about Grieg's life: What Price Immortality? (1999), Song of Norway (1970)
• Edvard Grieg picture collection at flickr commons

Recordings by Edvard Grieg[link]

• Papillon – Lyric Piece, Op. 43, no. 1 as recorded by Grieg on piano roll, 17 April 1906, Leipzig (Info)
• Legendary Piano Recordings: The Complete Grieg, Saint-Saëns, Pugno, and Diémer (Marston Records)
• Edvard Grieg: The Piano Music In Historic Interpretations (SIMAX Classics – PSC1809)
• Grieg and his Circle (Pearl, GEMM 9933 CD)
• Grieg spiller Grieg (Edvard Grieg Museum Troldhaugen)
• Piano Rolls (The Reproducing Piano Roll Foundation)

Music scores[link]

• Free scores by Edvard Grieg at the International Music Score Library Project
• Free scores by Edvard Grieg in the Werner Icking Music Archive (WIMA)
• Free scores by Edvard Grieg in the Choral Public Domain Library (ChoralWiki)
• Free scores at the Mutopia Project

polski:Edvard Grieg

Daphne Koller
Residence	United States
Nationality	American
Fields	Machine Learning
Institutions	Stanford University
Alma mater	Stanford University (1993, PhD) Hebrew University of Jerusalem (1986, MS)
Doctoral advisor	Joseph Halpern
Doctoral students	Eran Segal

Daphne Koller (born 1968 or 1969) is a Professor in the Department of Computer Science at Stanford University^[1] and a MacArthur Fellowship recipient. She's also one of the founders of Coursera, an online education platform. Her general research area is artificial intelligence^[2][3] and its applications in the biomedical sciences^[4][5]. Koller was featured in an article by MIT Technology Review titled "10 Emerging Technologies That Will Change Your World"^[6] concerning the topic of Bayesian Machine Learning.

She received a bachelor's degree from the Hebrew University of Jerusalem in 1985 and a Master's degree from the same institution in 1986.^[7]

Koller completed her Ph.D. at Stanford in 1993 under the supervision of Joseph Halpern, and joined the faculty of the Stanford University Computer Science Department in 1995. She was named a MacArthur Fellow in 2004.

In April 2008, Daphne Koller was awarded the first-ever $150,000 ACM-Infosys Foundation Award in Computing Sciences.^[8]

In 2009 she published a textbook on Probabilistic Graphical Models together with Nir Friedman.^[9] She will offer a free online course on the subject starting February 2012.^[10]

References[link]

William Leonard Roberts II (born January 28, 1976), better known by his stage name Rick Ross (often stylized as RICK RO$$), is an American rapper. He derived his stage name from the drug trafficker "Freeway" Ricky Ross, to whom he has no connection. Ross founded the record label Maybach Music Group, on which he released his studio albums Deeper Than Rap and Teflon Don, Ross was also the first artist signed to Diddy's management company Ciroc Entertainment. In early 2012, MTV named Ross as the Hottest MC In The Game.^[3]

Early life[link]

William Leonard Roberts II was born in Coahoma County, Mississippi.^[1] and raised in Carol City, Florida, near Miami.^[2] After graduating from Carol City Senior High School, he later attended the historically black college Albany State University on a football scholarship.^[4]

Music career[link]

After being signed to Suave House Records, former label for rap duo 8Ball & MJG, he eventually signed a deal with Slip-n-Slide Records, which has been under the Def Jam umbrella since 2006. While signed to Slip-n-Slide, Ross toured with fellow rapper Trick Daddy and made guest performances on other Slip-n-Slide albums.^[2]

[edit] Port of Miami (2006)

His debut album Port of Miami was released in August 2006 and debuted at the top spot on the Billboard 200 album chart, with sales at 187,000 units after its first week.^[5][6] Christian Hoard of Rolling Stone magazine predicted that it would be "the summer's biggest rap record".^[7] The second single was "Push It", which samples "Scarface (Push It to the Limit)", the theme song off the gangster film Scarface.^[8] The music video for "Push It" was modeled after the film.^[9] During that time, Ross made guest performances on two singles from DJ Khaled's debut Listennn... the Album: "Born-N-Raised" and "Holla at Me". Port of Miami received Gold certification from the Recording Industry Association of America on November 8, 2006.

[edit] Trilla (2008)

In March 2008, his second album Trilla was released and, as its predecessor Port of Miami had, debuted at the top of the Billboard 200.^[10] Its lead single "Speedin'" featuring R. Kelly peaked at #121 on the Billboard Hot 100; the next one, "The Boss" featuring T-Pain peaked at #17 on the Hot 100. The third single "Here I Am" featured Nelly and Avery Storm.^[11] MTV News ranked Ross on the fourth spot in its 2008 "Hottest MCs In The Game" list among ten rappers.^[12] The fourth single "This Is The Life" featured Trey Songz and was released in July.

[edit] Deeper Than Rap (2009)

"I look at the game and the business and all different aspects, it's a lot of great lyricists on the corner that will never properly understand the business and know how to market themselves and get in a position where they can gain capital. I look at all the strategies people use and what made them successful. What made Birdman just as relevant today after selling 50 million records? That intrigues me. To see the class of Jay-Z, his accomplishments and see how he sits backs and accurately makes his moves."^[13]

A track from the album called "Valley of Death" was what stood out to MTV reporters. In the song, Ross speaks briefly on his controversial stint as a prison guard. "Keep it trilla, nigga, never had a gun and badge," which he stresses, leaving the word that he was indeed an officer of the law. "Kept a nice watch, smoking on a hundred sack/ Back in the day I sold crack for some nice kicks/ Skippin' school, I saw my friend stabbed with an ice pick/ Can't criticize niggas trying to get jobs/ Better get smart, young brother, live yours." Later, he implies that while he was working as a corrections officer, he was on the streets. "Only lived once and I got two kids/ And for me to feed them, I'll get two gigs," he raps. "I'll shovel shit, I'll C.O./ So we can bow our heads and pray over the meatloaf." Although, he still provided no explanation for lying about being a C.O. to begin with, nor did he explain why he failed to pay child support for his children.^[14][15]

The cover of the May 2009 issue of XXL magazine, titled "Rick Ross Up in Smoke", featured Ross wearing a pair of Louis Vuitton sunglasses. After publication, a spokesperson for the luxury-goods maker contacted XXL to inform them that Ross was sporting fake sunglasses in the cover image.^[16] It was later revealed that the rapper was wearing authentic Louis Vuitton sunglasses which were altered by Jacob Bernstein, known as "The Sunglass Pimp". Bernstein defended his customizations despite Louis Vuitton's insistence that such modification and resale of trademarked property is not legal.^[17]

[edit] Teflon Don and other works (2010)

Rick Ross released his fourth studio album entitled Teflon Don, which was released on July 6, 2010. The lead is "Super High" featuring Ne-Yo. Actress Stacey Dash made an appearance in the music video. A second official single was released titled "Live Fast, Die Young" which features and is produced by Kanye West. The album debuted at #2 on the Billboard 200 selling 176,000 copies in its first week.

In November 2010, rapper and frequent collabourator, Diddy, who in 2009 signed Ross to a management deal with his Ciroc Entertainment, announced from his YouTube account, that him and Ross are working on an EP together, which is going to be released in 2011.^{[dated info]} A single has been released for the project, called "Another One".^[18]

[edit] God Forgives, I Don't (2011 - present)

Rick Ross had also announced the release of his next album, "God Forgives, I Don't", for December 13, 2011, however it was confirmed on November 17, 2011 it has been pushed back for release in 2012.^[19][20]

Rick Ross premiered two songs from his new album "God Forgives, I Don't", titled "You The Boss" and "I Love My Bitches".^[21]

Along with his music projects, Rick Ross was nominated by The Source as its "Man of the Year".^[22]

Rick Ross performed at BET Awards 2011, which aired on June 26, 2011.^[23] He also received a nomination for Best Male Hip Hop Artist.^[24] In early 2012, Ross was named the Hottest MC In The Game.^[3]

Personal life[link]

Correctional officer photos[link]

In July 2008, The Smoking Gun produced details linking Ross' social security number to an eighteen month stint as a correctional officer at the South Florida Reception Center, along with a photograph purporting to be Ross in his correctional officer uniform.^[25] Ross initially denied that the photograph was of him;^[26] after overwhelming evidence of his past came into the public's eye, Ross later admitted that he did work as a correctional officer in Florida during the early 1990s.^[27] In a 2008 interview with AllHipHop.com,^[28] "Freeway" Ricky Ross, claimed offense that Roberts used his name and identity when he learned that The Smoking Gun posted documents revealing Roberts' previous employment as a Florida correctional officer.^[29]

Legal issues[link]

Mugshot of Rick Ross taken in 2008.

In January 2008, Ross was arrested on gun and marijuana charges. During a deposition of Officer Rey Hernandez, a Miami Beach cop who arrested Ross, Ross's lawyer, Allan Zamren, asked Hernandez why Ross’s case was assigned to the gang task force. The officer stated that it was because Ross claimed affiliation with Carol City Cartel and other known gang members. Zamren then pressed Hernandez for a personal link between Ross and the gang members, but ultimately one could not be established.^[30]

In August 2008, YouTube entertainer DJ Vlad filed a lawsuit against Ross for assault and battery. Vlad claimed Ross organized an ambush on him at the 2008 Ozone Awards in Houston, Texas for asking questions about his past as a correctional officer.^[31]

On June 18, 2010, Freeway Ricky Ross sued Rick Ross for using his name,^[32] filing a copyright infringement lawsuit in a California Federal Court.^[32] Jay-Z had been called to testify in the lawsuit, as he was CEO of Def Jam when Ross/Roberts was signed.^[32] The reformed drug kingpin was looking for 10 million dollars in the lawsuit.^[32] Also, the release of his album, Teflon Don, was threatened to be blocked by Freeway Ricky Ross. A week after the filing of the lawsuit, Rick Ross responded to the charges: "It’s like owning a restaurant, you’re gonna have a few slip and falls. You get lawsuits, you deal with them, and get them out your way…sometimes you lose."^[33] He then denied rumors that he would change his name to "Ricky Rozay" as a consequence of the lawsuit. The lawsuit was thrown out of court on July 3, 2010^[34] and his album, Teflon Don, was released on July 20 as scheduled.

On March 26, 2011, Ross was arrested in Shreveport for possession of marijuana. According to the police records, a strong odor of marijuana was detected from his room at the Hilton in Downtown Shreveport.^[35]

Religion[link]

Rick Ross is a Christian,^[36] and in an interview with Corey "Coco Brother" Condrey on Lift Every Voice, he indicated that "I had told myself at one point no matter what I go through, I never question God."^[37] In addition, Ross indicated that he prays every time he goes on stage to perform.^[38]

Seizures[link]

On October 14, 2011 Rick Ross suffered two seizures in the same day, once in the morning and once again early evening. Following the morning seizure, he was unconscious and CPR was being performed. He did, however, post a video to his Twitter account later in the day saying that he was OK.^{[citation needed]} Ross boarded another plane later in the day and suffered another seizure. On October 14, the University of Alabama at Birmingham Hospital confirmed that Ross had been admitted to the emergency room. TMZ, who first reported the seizure, updated their story originally posted at 4:45 PST, stating that Ross was in stable condition.^{[citation needed]}

Feud with 50 Cent[link]

In January 2009, Ross started a feud with rapper 50 Cent because he supposedly looked at him the wrong way at the BET Awards. 50 Cent told news sources that he did not remember seeing Ross there.^[39] In late January, "Mafia Music", by Ross, leaked onto the Internet. There were several lines that seemed to diss 50 Cent. Days later, 50 Cent released "Officer Ricky (Go Head, Try Me)" in response to Ross's disparaging remarks on his "Mafia Music" song.

Before going to Venezuela, 50 Cent uploaded a video entitled "Warning Shot," wherein he stated: "Rick Ross- I'mma fuck your life up for fun." In addition, 50 Cent released the first of a series of "Officer Ricky" cartoons. Early in February, 50 Cent once again made a video which he uploaded to YouTube in which he interviewed "Tia", the mother of one of Ross's children. She verifies that he was a correctional officer and claims his whole persona is fake and fraudulent.^[40] On Thursday, February 5, 2009, Game, who 50 Cent has a long-standing "beef" with, called up Seattle R&B station KUBE. When asked about the beef between 50 Cent and Ross, Game sided with 50 Cent and said that things are not looking good for Ross. He offered to help, stating, "Rick Ross, holla at your boy, man," and, "50 eating you, boy."^[41] On his album Deeper Than Rap, Ross references 50 Cent in the song "In Cold Blood". A video for the song was released that portrayed 50 Cent's mock funeral. Upon release, Ross stated that he has ended 50 Cent's career.^[42] That same day Ross released a new diss track called "Push 'Em Over The Edge". The next day 50 Cent released the controversial video "A Psychic Told Me", dissing DJ Khaled. On February 12, 50 Cent responded with "Tia Told Me", along with Lloyd Banks' response "Officer Down" and Tony Yayo's "Somebody Snitched".

In an interview, 50 Cent said Ross is "Albert From CB4. You ever seen the movie? He's Albert," he added. "It never gets worse than this. You get a guy that was a correctional officer come out and base his entire career on writing material from a drug dealer's perspective."^[43]

Discography[link]

Solo albums[link]

• 2006: Port of Miami
• 2008: Trilla
• 2009: Deeper Than Rap
• 2010: Teflon Don
• 2012: God Forgives, I Don't ^[20]

Maybach Music Group Albums[link]

• 2011: Self Made Vol. 1 (with Maybach Music Group)
• 2012: Self Made Vol. 2 (with Maybach Music Group)^[44]

Collaboration albums[link]

• 2009: Custom Cars & Cycles (with Triple C's)
• TBA: Bugatti Boyz (with Diddy)^[45][46]

Compilation albums[link]

• 2007: Rise to Power

References[link]

External links[link]

Wikimedia Commons has media related to: Rick Ross

• Rick Ross Official Def Jam Website
• Rick Ross at the Internet Movie Database