Webservices And Soa Principles And Technology Pdf Download
Robert Bhushan
Parts of the web platform evolve independently.Issues that are present with a certain web technology now may be fixed in a subsequent iteration.Duplicating these issues makes fixing them more difficult.By adhering to this principle we can make sure overall platform quality improves over time.
There is often a tension between internal and external consistency. Internal consistency is consistency with the rest of the system,whereas external consistency is consistency with the rest of the world.In the web platform, that might materialize in three layers:consistency within the technology the API belongs to (e.g. CSS),consistency with the rest of the web platform,and in some cases external precedent,when the API relates to a particular specialized outside domain.In those cases, it is useful to consider what the majority of users will be.Since for most APIs the target user is someone who is familiar with thetechnology they are defined in,err on the side of favoring consistency with that.
One of the advantages of using Uniform Resource Identifiers (URIs) is that they can be dereferenced using the HTTP protocol. According to the so-called Linked Open Data principles, such a dereferenced URI should result in a document that offers further data about the given URI. In this example, all URIs, both for edges and nodes (e.g. , , ) can be dereferenced and will result in further RDF graphs, describing the URI, e.g. that Dresden is a city in Germany, or that a person, in the sense of that URI, can be fictional.
The first research group explicitly focusing on the Corporate Semantic Web was the ACACIA team at INRIA-Sophia-Antipolis, founded in 2002. Results of their work include the RDF(S) based Corese[49] search engine, and the application of semantic web technology in the realm of distributed artificial intelligence for knowledge management (e.g. ontologies and multi-agent systems for corporate semantic Web) [50] and E-learning.[51]
WCAG 2.1 success criteria are written as testable statements that are not technology-specific. Guidance about satisfying the success criteria in specific technologies, as well as general information about interpreting the success criteria, is provided in separate documents. See Web Content Accessibility Guidelines (WCAG) Overview for an introduction and links to WCAG technical and educational material.
The individuals and organizations that use WCAG vary widely and include Web designers and developers, policy makers, purchasing agents, teachers, and students. In order to meet the varying needs of this audience, several layers of guidance are provided including overall principles, general guidelines, testable success criteria and a rich collection of sufficient techniques, advisory techniques, and documented common failures with examples, resource links and code.
Principles - At the top are four principles that provide the foundation for Web accessibility: perceivable, operable, understandable, and robust. See also Understanding the Four Principles of Accessibility.
Guidelines - Under the principles are guidelines. The 13 guidelines provide the basic goals that authors should work toward in order to make content more accessible to users with different disabilities. The guidelines are not testable, but provide the framework and overall objectives to help authors understand the success criteria and better implement the techniques.
All of these layers of guidance (principles, guidelines, success criteria, and sufficient and advisory techniques) work together to provide guidance on how to make content more accessible. Authors are encouraged to view and apply all layers that they are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.
The way that the Web content technology is used must be supported by users' assistive technology (AT). This means that the way that the technology is used has been tested for interoperability with users' assistive technology in the human language(s) of the content,
The content is available in a closed environment, such as a university or corporate network, where the user agent required by the technology and used by the organization is also accessibility supported;
Determined from technology-specific data structures in a non-markup language and exposed to assistive technology via an accessibility API that is supported by commonly available assistive technology.
For example, CMS advises service developers to expose information using a Message Model that is a different schema than the data storage model. This decouples the interface from implementation, allowing for greater flexibility and migration to different implementations. By contrast, coupling service consumers to the data source implementation limits implementation options in the future, such as migration to new technology, or database consolidation.
N2 - Web services allow new and improved ways for enterprise applications to communicate and integrate with each other over the Web and, as such, are having a profound effect on both the worlds of business and of software development.The new edition of this bestselling book offers a comprehensive and up to date treatment of web services and Service Oriented Architecture (SOA), giving you all you need to know to gain a solid foundation in this area. Building upon the clear, accessible approach of the first edition, it provides a complete introduction to the concepts, principles, technology and standards of web services. The book also provides an in depth examination of good design and development practises for SOA applications in organisations.
AB - Web services allow new and improved ways for enterprise applications to communicate and integrate with each other over the Web and, as such, are having a profound effect on both the worlds of business and of software development.The new edition of this bestselling book offers a comprehensive and up to date treatment of web services and Service Oriented Architecture (SOA), giving you all you need to know to gain a solid foundation in this area. Building upon the clear, accessible approach of the first edition, it provides a complete introduction to the concepts, principles, technology and standards of web services. The book also provides an in depth examination of good design and development practises for SOA applications in organisations.
SOA is not a new concept. Sun defined SOA in the late 1990's to describe Jini, which is an environment for dynamic discovery and use of services over a network. Web services have taken the concept of services introduced by Jini technology and implemented it as services delivered over the web using technologies such as XML, Web Services Description Language (WSDL), Simple Object Access Protocol (SOAP), and Universal Description, Discovery, and Integration(UDDI). SOA is emerging as the premier integration and architecture framework in today's complex and heterogeneous computing environment. Previous attempts didn't enable open interoperable solutions, but relied on proprietary APIs and required a high degree of coordination between groups. SOA can help organizations streamline processes so that they can do business more efficiently, and adapt to changing needs and competition, enabling the software as a service concept. eBay for example, is opening up its web services API for its online auction. The goal is to drive developers to make money around the eBay platform. Through the new APIs, developers can build custom applications that link to the online auction site and allow applications to submit items for sale. Such applications are typically aimed at sellers, since buyers must still head to ebay.com to bid on items. This type of strategy, however, will increase the customer base for eBay.
Sun has recognized the challenges customers face in moving to SOA and has developed an SOA Opportunity Assessment service offering that leverages years of experience in delivering enabling technology solutions that met the unique needs of each customer. Sun's SOA Opportunity Assessment provides customers with an analysis of their organization's readiness to move to SOA, and a set of best practices developed to complement this service offering, and helps them identify business-relevant opportunities for building their service-oriented applications using architectural best practices and reusable design patterns. For more information on this as well as additional Sun SOA services offerings.
Enterprises have invested heavily in large-scale packaged application software such as enterprise resource planning (ERP), supply chain management (SCM), customer relationship management (CRM), and other systems to run their businesses. IT managers are being asked to deliver the next generation of software applications that will provide new functionality, while leveraging existing IT investments. The solution to this is integration technology; the available integration technology solutions, however, are proprietary and do not interoperate with each other. The advent of web services and SOA offers potential for lower integration costs and greater flexibility.
JSR 208 Java Business Integration (JBI), is a specification for a standard that describes plug-in technology for system software that enables a service-oriented architecture for building integration server software. JBI adopts SOA to maximize the decoupling between components, and create well-defined interoperation semantics founded on standards-based messaging. JSR 208 describes the service provider interfaces (SPIs) that service engines and bindings plug into, as well as the normalized message service that they use to communicate with each other. It is important to note that JSR 208 doesn't define the engines or tools themselves. JSR 208 has the following business advantages:
Sustainable web design is an approach to designing web services that puts people and planet first. It delivers digital products, services, and data that respect the principles of the Sustainable Web Manifesto: clean, efficient, open, honest, regenerative, and resilient.
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