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Geoinformatics-8-2009
article figure 1. comparison of normalized response time of google app engine (blue) and local (red) deployed wps over number of simultaneous requests. outtasking by outtasking software and data to scalable facilities operated by third parties, users and customers don't have to operate their own datacenters anymore. therefore, enterprises of all types can decrease their infrastructure costs enormously. they can take advantage of transforming their fixed it costs into variable costs as a business advantage by focusing on their core business. scalability the allocation of cloud resources is done in real time and most cloud infrastructures scale deployed applications automatically on demand (for example in case of high request rates). this gives cloud users and cloud application providers the option of handling peak load very efficiently without operating their own datacenter and without managing their own infrastructure. on-demand allocating cloud resources on a real time and on-demand basis helps enterprises to scale up their business capacities in a quick and efficient way. the absence of long-term contracts in combination with pay-per-use revenue models allows the low-cost start-up of new ideas for business models. the total cost of ownership of self-hosted datacenters minimizes start-up costs and helps enterprises to put new promising business models into the market. additional features of cloud computing infrastructures are the application of service level agreements (sla). such contracts are important for cost-performance ratio transparency and therefore an essential skill for all kinds of it and it-based geospatial business models. in essence, cloud computing is not a completely new concept. under the umbrella of the latest news? visit www.geoinformatics.com term cloud computing a family of well known and established methods and technologies is collected. for example software as a service (saas) as a model for software deployment and virtualization as an efficient hosting platform. besides, it describes a paradigm of outsourcing applications and specific tasks to a scalable infrastructure and therefore consequently enabling new business models with less upfront investments. there are still a number of open issues for cloud computing. one deals with the general barriers of adopting cloud computing and is examined for example in the so-called "open cloud manifesto". besides data backup and recovery responsibilities, the outsourcing of confidential and economically relevant data from data owners facilities to third party infrastructures is always problematic in context of trust. using public clouds as a deployment platform for applications in risk management scenarios is a security issue in situations when the underlying cloud suffers an outage. specific applications and can be scaled ondemand to handle peak load. the amazon simple storage service (amazon s3) provides a web services interface that can be used to store and retrieve large amounts of data (dsaas). the amazon elastic mapreduce is a web service that offers computational power to process efficiently vast amounts of data. in contrast to aws, the google app engine is an adequate example for pure paas. the google app engine provides a sandbox for running java- and python-based web applications. the web applications are deployed on the google infrastructure so they can take advantage of the same scalable and load balancing technologies that usual google applications are built on. on the one hand, the key advantage of google app engine is that google app engine offers an easy way of deploying web applications in the cloud. in particular, the overhead of dealing with virtual machines and entire (virtual) server systems could be ignored. on the other hand, applications deployed in the google app engine are restricted to a specific (java- or pythonbased) application framework that runs in a restricted sandbox limiting, for example, the web service request duration. different projects and initiatives drive the general development of cloud computing technologies and open standards for interoperability in clouds. the open cloud consortium (occ) is an initiative dedicated to cloud interoperability and initiated the open cloud test bed. the open cirrus project is a cloud computing research test bed between research and industry partners. in the eucalyptus initiative, an open source-based implementation of the amazon api is under development. 2.3 web processing service the open geospatial consortium (ogc) web processing service interface specification (ogc 2007) describes a standardized method to publish and execute web-based processes for any type of geoprocesses. according to the wps interface specification, a process is defined as any calculation operating on spatially referenced data. in detail, the wps interface specification describes three operations: getcapabilities, describeprocess and execute. getcapabilities is common to any type of ogc web service and returns service metadata. in the case of wps it also returns a brief description of the processes offered by the specific service instance. to get more information about the hosted processes, the wps provides process metadata through the describeprocess operation. this operation describes all parameters, which are required to run the process. based on this information the client can perform the execute operation upon the designated process. as every december 2009 2.2 projects and initiatives a lot of enterprise corporations are trying to get into the cloud computing business by offering services to access their huge and grown over the years infrastructures. microsoft with the azure services platform, ibm introduced its "blue cloud" platform and sun for example offers cloud computing solutions as well. in this chapter we describe the cloud solutions from amazon and google in more detail. the amazon web services (aws) product is a collection of services that are offering infrastructure as a service (iaas), datastorage as a service (dsaas) and some aspects of platform as a service (paas). the amazon elastic compute cloud (amazon ec2) provides a web service interface to manage virtual machines (iaas) that are used to host customer- 25
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