- The evolution of the Grid. - These aspects of the Grid are related to the evolution of Web technologies and standards, such as XML to support machine-to-machine communication and the Resource Description Framework (RDF) to represent interchangeable metadata.. - In Section 3.5 we draw parallels with the evolution of the World Wide Web and introduce the notion of the ‘Semantic Grid’ in which semantic Web technologies provide the infrastructure for Grid applications. - 3.2 THE EVOLUTION OF THE GRID: THE FIRST GENERATION. - The origin of the term is believed to have been the CASA project, one of several US Gigabit test beds deployed around 1989. - The early to mid 1990s mark the emergence of the early metacomputing or Grid envi- ronments. - The two projects also attempted to pro- vide metacomputing resources from opposite ends of the computing spectrum. - To keep abreast of the state of the art in factoring, RSA Data Security Inc. - The Factoring Challenge provides a test bed for factoring implementations and provides one of the largest collections of factoring results from many different experts worldwide.. - Contributors could, from one set of Web pages, access a wide range of support services for the sieving step of the factorisation: NFS software distribution, project documentation, anonymous user registration, dissemination of sieving tasks, collection of relations, relation archival services and real-time sieving status reports. - It also had an ATM interface that allowed monitoring and potential management of the site’s ATM switch.. - I-Soft was a success in terms that most applications ran, most of the time. - More importantly, the experiences and software developed as part of the I-WAY project have been fed into the Globus project (which we discuss in Section 3.2.2).. - Both FAFNER and I-WAY attempted to produce metacomputing environments by integrat- ing resources from opposite ends of the computing spectrum. - In addition, the I-POP platform and server created one, of many, single points of failure in the design of the I-WAY. - Even though this was not reported to be a problem, the failure of an I-POP would mean that a site would drop out of the I-WAY environment.. - Each project was in the vanguard of metacomputing and helped pave the way for many of the succeeding second-generation Grid projects. - FAFNER was the forerunner of the likes of SETI@home [7] and Distributed.Net [8], and I-WAY for Globus [9] and Legion [10].. - 3.3 THE EVOLUTION OF THE GRID: THE SECOND GENERATION. - The emphasis of the early efforts in Grid computing was in part driven by the need to link a number of US national supercomputing centres. - This vision of the Grid was presented in Reference [11] and we regard this as the second generation, typified by many of today’s Grid applications.. - In this section, we consider the second-generation requirements, followed by repre- sentatives of the key second-generation Grid technologies: core technologies, distributed object systems, Resource Brokers (RBs) and schedulers, complete integrated systems and peer-to-peer systems.. - Traditionally, it is the huge scale of the data and computation, which characterises Grid applications.. - The main design features required at the data and computational fabric of the Grid are the following:. - A major goal is to make all resources accessible to any process in the system, without regard to the relative location of the resource user. - The Grid information (registration and directory) services provide the mechanisms for registering and obtaining information about the structure, resources, services, status and nature of the environment.. - The overall aim is the efficient and effective scheduling of the applications that need to utilise the available resources in the distributed environment. - Here we identify some of the most significant to date.. - A central element of the Globus system is the Globus Toolkit, which defines the basic services and capabilities required to construct a computational Grid. - The Globus Toolkit currently consists of the following (the precise set depends on the Globus version):. - An extended version of the file transfer protocol, GridFTP, is used for data access;. - The evolution of Globus is continuing with the introduction of the Open Grid Services Architecture (OGSA) [12], a Grid architecture based on Web services and Globus (see Section 3.4.1 for details).. - One of the concerns about CORBA is reflected by the evidence of intranet rather than Internet deployment, indicating difficulty crossing organi- sational boundaries. - Furthermore, real-time and multimedia support were not part of the original design.. - numerics and concurrency) are being addressed by the likes of the Java Grande Forum (a ‘Grande Application’ is ‘any application, scientific or industrial, that requires a large number of computing resources, such as those found on the Internet, to solve one or more problems’) [15]. - Thus, what is lost in computational speed might be gained in terms of software development and maintenance times when taking a broader view of the engineering of Grid applications.. - The actual implementation of the service can be in hardware, software, or both. - A fuller list of the available software can be found elsewhere [18, 19].. - A key feature of the SRB is that it supports metadata associated with a distributed file system, such as location, size and creation date information. - The users can set the deadline by which time their results are needed and the Nimrod-G broker tries to find the best resources available in the Grid, uses them to meet the user’s deadline and attempts to minimize the costs of the execution of the task.. - The purpose of the Collaboration is to support a common set of components and utilities to make portal development easier and to allow various portals to interoperate by using the same core infrastructure (namely, the Grid Security Infrastructure (GSI) and Globus).. - This section of the chapter discusses a representative set of these projects.. - The objectives of the DataGrid project are. - The final version of the DataGrid software is scheduled for release by the end of 2003.. - UNICORE jobs and job groups carry the information of the destination system for the included tasks. - The objectives of the EuroGrid project include the support of the EuroGrid software infrastructure, the development of software components, and demonstrations of distributed simulation codes from different application areas (biomolecular simulations, weather prediction, coupled CAE simulations, structural analysis and real-time data processing).. - WebFlow [39, 40] is a computational extension of the Web model that can act as a framework for wide-area distributed computing. - The frontend uses applets for authoring, visualization, and con- trol of the environment. - Peer-to-Peer (P2P) computing [43] (as implemented, for example, by Napster [44], Gnutella [45], Freenet [46] and project JXTA [47]) and Internet computing (as implemented, for example, by the SETI@home [7], Parabon [48], and Entropia systems [49]) are examples of the more general computational structures that are taking advantage of globally distributed resources.. - Another issue is the ability to authenticate the identity of the machines with their peers.. - One of the biggest challenges with P2P computing is enabling devices to find one another in a computing paradigm that lacks a central point of control. - Network-enabled operating environment consists of the JVM, which provides TCP/IP services and other resources to participate in a network.. - 3.3.8 A summary of experiences of the second generation. - 3.4 THE EVOLUTION OF THE GRID: THE THIRD GENERATION. - As further Grid solutions were explored, other aspects of the engineer- ing of the Grid became apparent. - In fact, the service-oriented approach itself has implications for the information fabric: the flexible assembly of Grid resources into a Grid applica- tion requires information about the functionality, availability and interfaces of the various components, and this information must have an agreed interpretation that can be processed by machine. - For further discussion of the service-oriented approach, see the companion. - The third generation is a more holistic view of Grid computing and can be said to address the infrastructure for e-Science – a term that reminds us of the requirements (of doing new science, and of the e-Scientist) rather than the enabling tech- nology. - The creation of Web services standards is an industry-led initiative, with some of the emerging standards in various states of progress through the World Wide Web Consortium (W3C). - However, Web services do not provide a new solution to many of the challenges of large-scale distributed systems, nor do they yet provide new techniques for the engineering of these systems. - The OGSA activity sits on one side of the triangle in Figure 3.1, and we suggest agent-based computing [64] as another important input to inform the service-oriented Grid vision.. - One of the techniques for achieving this is on-the-fly negotiation between agents, and there is a significant body. - The Web’s information handling capabil- ities are clearly an important component of the e-Science infrastructure, and the Web infrastructure is itself of interest as an example of a distributed system that has achieved global deployment. - It is interesting to consider the rapid uptake of the Web and how this might inform the design of the Grid, which has similar aspirations in terms of scale and deployment.. - We should, however, be aware of a dramatic contrast between Web and Grid: despite the large scale of the Internet, the number of hosts involved in a typical Web transaction is still small, significantly lower than that envisaged for many Grid applications.. - Version control : The popular publishing paradigm of the Web involves continually updating pages without version control. - Digital rights management : e-Science demands particular functionality with respect to management of the digital content, including, for example, copy protection and intellectual property management.. - Curation: Much of the Web infrastructure focuses on the machinery for delivery of information rather than the creation and management of content. - Together this provides the infrastructure for the information aspects of the third-generation Grid.. - ‘The Semantic Web is an extension of the current Web in which information is given well-defined meaning, better enabling computers and people to work in cooperation. - One of the collaborative aspects builds on the idea of a ‘collaboratory’, defined in a 1993 US NSF study [74] as a. - However, in practice, part of the Web phenomenon has been widespread publishing by the users. - In this context, however, the emphasis is on facilitating distributed collaboration, and we wish to embrace the increasingly ‘smart’ workplaces of the e-Scientist, including meeting rooms and laboratories. - This research area falls under the ‘Advanced Collaborative Envi- ronments’ Working group of the GGF (ACE Grid), which addresses both collaboration environments and ubiquitous computing.. - Another source of live information is the notes taken by members of the meeting, or the annotations that they make on existing documents. - In this chapter, we have identified the first three generations of the Grid:. - Third-generation systems are adopting a service-oriented approach, adopt a more holis- tic view of the e-Science infrastructure, are metadata-enabled and may exhibit auto- nomic features.. - The evolution of the Grid has been a continuous process and these generations are not rigidly defined – they are perhaps best distinguished by philosophies rather than tech- nologies. - We have seen that in the third generation of the Grid, the early Semantic Web technolo- gies provide the infrastructure for Grid applications. - The state of play of the Grid today is reminiscent of the Web some years ago: there is limited deployment, largely driven by enthusiasts within the scientific community, with emerging standards and a degree of commercial uptake. - The same might also be said of the Semantic Web. - The visions of the Grid and the Semantic Web have much in common but can perhaps be distinguished by a difference of emphasis: the Grid is traditionally focused on computation, while the ambitions of the Semantic Web take it towards inference, proof and trust. - This particular representation of the Semantic Grid is due to Norman Paton of the University of Manchester, UK.. - Figure 3.2 The Semantic Grid.. - The Semantic Grid involves all three conceptual layers of the Grid: knowledge, infor- mation and computation/data. - The general view of the Grid is that of a three-layered system made up of computa- tion/data, information and knowledge layers. - A certain number of these aspects are now being addressed as the information and knowledge layers of the Grid evolve. - At the information layer, although many of the technologies are available today (even if only in a limited form), a number of the topics still require further research. - Hence, the knowledge layer is key to the next stage in the evo- lution of the Grid, to a fully fledged Semantic Grid. - The research agenda to create the Semantic Grid is the subject of the companion paper ‘The Semantic Grid: A Future e-Science Infrastructure’.. - (2001) The anatomy of the Grid: enabling scalable vir- tual organizations. - Communications of the ACM . - (2002) The Physiology of the Grid: Open Grid Services Architecture for Distributed Systems Integration, Presented at GGF4, February, 2002, http://www.globus.og/research/papers/ogsa.pdf.. - Proceedings of the 8th High Performance Distributed Computing (HPDC. - Proceedings of the 1st IEEE/ACM Interna- tional Workshop on Grid Computing (Grid 2000), Bangalore, India, December Germany: Springer-Verlag.. - Proceedings of the Ninth International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS 2000), November, 2000.. - Proceedings of the Eleventh International Workshop on Network and Operating System Support for Digital Audio and Video (NOSSDAV 2001), June, 2001.. - Proceedings of the 4th USENIX Symposium on Operating Systems Design and Implementation (OSDI 2000), San Diego, CA, October, 2000.. - Com- munications of the ACM . - Proceedings of the Second Workshop on Advanced Collaborative Environments, Eleventh IEEE Int
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