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Web Services Description Language acronym is used to describe a Web service and how to communicate with Web Services XML language. Interface to provide users with detailed instructions.
Web Services Description Language acronym is used to describe a Web service and how to communicate with Web Services XML language. Interface to provide users with detailed instructions.
STR/04/059/SP Web Services Technology for the Industry P. S. Tan and E. W. Lee Abstract – Web Services is the latest buzzword IHLs Institutes of Higher Learning that has been touted by many as the next tech- IT Information Technology nology revolution in IT that can solve a multitude of problems that are inherent today. Neverthe- ISS Institute of Systems Science less, when the focus is shifted towards web ser- J2EE Java™ 2 Platform, Enterprise Edition vice adoption and implementation, web services JDK Java Development Kit has not reached mainstream. In the context of JSSL Java Smart Services Lab Singapore for example, the application and us- age of web services may have started. However, MIS Management Information Systems the widespread adoption and interoperability of OS Operating System web service-enabled applications are still some PKI Public Key Infrastructure way off. From the technology point of view, one SOA Service-Oriented Architecture of the major stumbling blocks have been the complexity surrounding web services as it SOAP Simple Object Access Protocol encompasses a myriad of technologies. In short, SSO Single Sign-On the learning curve can be very steep and devel- UAM User Access Management opment of web service-enabled applications can Universal Description, Discovery and be difficult. However the potential of web ser- UDDI Integration vices is boundless. W3C The World Wide Web Consortium The Java Smart Services Lab (JSSL)* was WSDL Web Services Description Language setup to help accelerate the adoption of web WSRA Web Service Reference Architecture services by the industry. To this end, a Web XML eXtensible Markup Language Service Reference Architecture (WSRA) has been developed to accelerate the technical and 1.2 Basic web services technology capabilities of the industry, and as a result, enable more web service implementa- tions. This report provides an introduction into If a search were executed on one of the Internet web services of today, and through its technol- search engines for “web service” or “web ser- ogy developed, JSSL’s vision of helping to vices”, it would probably return thousands and shorten the learning curve as well as accelerate thousands of hits. The same can be said for web web services adoption. services definition. For the work of JSSL, the following definition is used. * JSSL is a joint initiative between Singapore Institute of Manufacturing Technology (SIM- “Web service is a software component repre- Tech), Infocomm Development Authority (IDA) senting a specific business function that can be and Sun Microsystems. described, published and invoked over the net- work using open-‘standards’**.” Keywords: Web service(s), SOAP, WSDL, XML ** (Standards are issued by recognised stan- dards organisations, such as ISO for example. Here, ‘standards’ are either de-facto standards adopted by the IT industry or recommendations 1 BACKGROUND by organisations like W3C and OASIS.) 1.1 Common definition and notation By its very definition as a software component, it used means that implicitly, web services are built for aggregation or composition into larger web ser- Acronym Complete Name vice implementations or even Internet-based API Application Programming Interface applications. Although by definition web services can be invoked using different network proto- ASPs Application Service Providers cols, SOAP over HTTP is the currently the most HTTP Hypertext Transfer Protocol common communication method. IDCs Internet Data Centres 354 Web Services Technology for the Industry Fig. 1 diagrams a typical basic web service sce- Service Reference Architecture (WSRA) effort is nario that includes three categories of users, part of this technology development effort de- namely: fined under the initiatives of JSSL. The WSRA is • Service Providers a framework that is developed to fulfil two goals: This group is the web service creators or • To shorten the web service learning hosting agencies that host web services. In curve by providing good practices and iden- a typical environment, once the web ser- tifying the correct path(s) to follow in web vices are created they can be published to services development. This is especially discovery agencies, describing the service’s useful for beginners who are embarking on functionality, binding information as well as the Java web services journey. information about the creators. This is cur- • To accelerate web services development rently spelt out using the WSDL. by shortening the development of web ser- • Discovery Agencies vice-enabled applications through a set of This group can be described as middlemen foundation Core Services that can be used acting as brokers for service providers and as building blocks. requestors (or consumers). They serve as agencies or repositories for services with Based on the two objectives outlined, the WSRA appropriate description that can be discov- is designed in consideration to other efforts such ered by potential service requestors. The as the Web Services Architecture from W3C, de-facto description and query support is J2EE, Microsoft .NET framework and software currently based on UDDI. implementations, be it open-source or commer- • Service Requestors cial efforts. Fig. 2 illustrates the context of the These are the actual consumers of web ser- WSRA in relation to these efforts. The WSRA is vices. In a typical scenario, these consum- targeted at individuals or organisations that in- ers will look for services in the discovery tend to build web service-enabled applications. agencies. Upon locating suitable services, users will negotiate and co-ordinate usage 3 THE WEB SERVICE REFERENCE of these services directly with service pro- ARCHITECTURE (WSRA) viders. When an agreement is reached, ser- vice consumers can start using the services. The WSRA is a framework consisting of: Information in the WSDL is used to bind and • Infrastructural guidelines and invoke each web service. • Reference Implementation of Core Services with relevant accompanying specifications. UDDI WS -Apps WS -Apps WS-Apps WS -Apps WS -Apps Registries Discovery eb W Service … WS -Apps WS -Apps Discovery Applications … WS- WS- WS- WS- WS- Agencies Agencies WS- WS- (Publish) SOAP SOAP (Find) JSSL Web Service Reference Architecture WSDL Software Application/Web/Directory Servers, Middleware, Databases Service Service SOAP Service Service Providers Providers (Bind) Requestors Requestors Platform J2EE (Web Services) .NET WSDL W3C Web Services Architecture (WSA) Fig. 1. A basic web service environment. In each of the operations described, the de-facto Fig. 2. The positioning/context of web service refer- communication language or protocol is SOAP. ence architecture (WSRA). Also, in this scenario, an end-point or node can function in more than one role. For example, a It is based on open-standards and related tech- given node can be both a service requestor and nologies to facilitate the rapid creation and as- provider at the same time. sembly of interoperable web services. This framework spans four layers, namely Hardware and Networking, Operating System, Software 2 OBJECTIVE and Core Services layers, as shown in Fig. 3. As part of JSSL mission to help accelerate web In each of the layers, guidelines on configuration services adoption in Singapore, it was identified or usage techniques for web services are pro- that technology development is crucial. The Web vided. These are based on identified commercial solutions, and where possible, freeware or open- 355 Web Services Technology for the Industry source alternatives as well. The Core Services IT professionals who are moving into Java- layer forms the gist of the Reference Implemen- based web services, with guidelines on develop- tation in the WSRA. The Reference Implementa- ing web services that would be interoperable as tion can be divided into two parts, namely sets of well as deployable across different vendor plat- identified and implemented Core Services and forms. This guide  handles interoperability specifications of these Core Services. between Java-based implementations only and does not look into issues related to inter-platform 3.1 Infrastructural guidelines interoperability, like between Java and .NET platforms implementations for example. Presently, this section consists of 3 sets of iden- tified guidelines that can be used as references The importance of web service interoperability for the acceleration of web services develop- cannot be overstated and considerations should ment. They are in the area of web services in- start at the beginning, from requirements map- frastructure, interoperability and testing ping to architecting to designing, to implement- ing and testing of web services. As such, system 3.1.1 Adapting an IT infrastructure for web architects will find this guide very useful in identi- services guide fying the correct path to follow when starting on a web service-enabled application development. Individual vendors typically provide configuration Designers and developers who are embarking recommendation for its hardware, software or on web services development will also be able to even networking products. However, this is typi- use it as a handy reference. For example, this cally done in isolation and does not include the guide provides useful information on picking the holistic view of defining an IT infrastructure to correct web service signatures that can interop- meet the needs of an organisation or cluster of erate across multiple servers and the various organisations. In this area, the guide aims to supported XML data types by different servers. help organisations, which are keen to embrace It also recommends the type of web service cli- web services, to identify an adaptive IT infra- ents that should be developed and security con- structure that is web service-ready. It examines siderations that must be made to ensure better the issues surrounding the integration of web interoperability. services into an existing IT infrastructure and showcases a possible approach to adapting an 3.1.3 Web services testing guide existing IT infrastructure for web services . For example, due to the fact that web services Web Services, just like it peers in the SOA are more processing and bandwidth intensive, world, changes the way applications are devel- there is a need to cater for more hardware proc- oped. A paradigm shift from complete build to essing power in hosting servers and potentially assemble where possible (through reuse) and more network bandwidth to maintain the same build only when necessary is evident. With this level of performance. Also, older firewalls and change, it is also important to change the way routers that are not XML-aware may not protect software quality is ensured. One, it is important web service-applications from hacks, and as that formal testing must now be shifted towards such advisable to make provision for such more granular testing at component or service needs. level. Another important aspect found is that service aggregation can impact on the perform- The guide is mainly targeted at System and MIS ance of the whole application developed. Also, managers that need to understand the require- with the addition of the SOAP messaging layer ments of web services and plan for the IT infra- in web services, there is also a need to test for structure needs of their respective organisations SOAP compatibility and interoperability between that want to adopt a web service-enabled IT web services. For example, instead of system framework and strategy. System architects and test, a typical “application-like” testing scenario system engineers who need to gain a better in- would be to test for the interoperability of aggre- sight will also find this guide useful. gated services that can reside across firewalls and in heterogeneous environment. 3.1.2 Web services interoperability guide Today, tools for the creation of web services on the Java platform are widely available. However, as standards are still evolving, there are a myr- iad of ways to create and deploy web services, not to mention the aggregation or assembly of web services. To this end, JSSL aims to assist 356 Web Services Technology for the Industry Interoperability Core Services Reference Implementation (+ Specifications) Infrastructure Software Web/ Application Servers, Middleware, Databases Testing WSRA OS OS Environment Hardware Hardware / Networking Environment Guidelines Fig. 3. The web service reference architecture (WSRA) stack. In this guide , various aspects that are impor- vices are generic in nature and meant to be tant in the planning of a test-bed environment for used as building blocks in web service- testing (including web services) are shared. Its enabled applications. main target is software-testers, although system • Each Core Service has a predefined set of architects will find the considerations identified in API calls that are mapped into SOAP calls this guide valuable too. A section of this guide where possible or relevant. In other words, also shares the infrastructure that JSSL has put where applicable, each web service-enabled in place and the very insightful and painful ex- Core Service must be designed to support periences that she has undergone. As part of invocation over the Internet using SOAP and this experience sharing, examples of results support multiple concurrent users with multi- from the web service performance profiling tests namespace concept. are also made available. • Each Core Service on the lower layer cannot call or be dependent on a Core Service that 3.2 Reference implementation of core resides in a higher layer of the architecture, services as illustrated in Fig. 4. The Reference Implementation can be divided SOAP interfaces are designed based on the into two parts, namely sets of, identified and im- guidelines provided in the Web Services Inter- plemented, Core Services and accompanying operability Guide mentioned in section 3.1.2. specifications. The software serves as a toolkit or foundation to accelerate the development of web services enabled applications, whereas the specifications serve as a reference guide to the Layer 3 Service-3a Service-3b … Service-3n architecture and requirements of the imple- mented Core Services. The Core Services in the X Reference Implementation are developed using the component-based approach, and supports Layer 2 Service-2a Service-2b … Service-2n the concept of plug-and-play based on the J2EE platform. X 3.2.1 Design principles overview Layer 1 Service-1a Service-1b … Service-1n The Core Services are designed based on a Inter-layer Dependency Intra-layer Dependency x edDependency Disallow loosely coupled SOA concept and the layered architecture model , with the following princi- Fig. 4. Layers dependency rules. ples: • Each Core Service is designed as a soft- 3.2.2 The core services ware component, i.e. an independent piece of software that can be deployed individu- Using the design principles stated in section ally, based on explicit external dependencies 3.2.1, the Core Services are categorised into that are specified. Common and Value-Added Services Layers. In • Each Core Service provides a placeholder the Common Layer resides a set of services that for its functionality that is labelled as passive are usually associated with frequently used util- framework, i.e. it does not store information ity-like functionality, such as log, search, sensory or have information on calling services or (or detection) of devices and notification for ex- applications. This is necessary as Core Ser- ample. A Service-Tester is included and meant 357 Web Services Technology for the Industry to be used as a utility to check the availability to develop web services, including the de- and performance of web services over the HTTP velopment of web services on the Java plat- protocol dynamically. The Value-Added Layer form. After this course, individuals should consists of services that are likely to be needed have a good grasp of web services and able in any application development, including the to start developing simple web services. management of users and services under the • Module 2 – Web Services Development purview of the application domain. For more ad- Workshop vanced management needs, services such as This module is designed to cater for devel- Roles & Access Management, Service Man- opers and designers who have some knowl- agement that includes service monitoring and a edge of web services and want an intensive Web Service Aggregator to handle assembly or form of training to fine-tune and hone their aggregation of web services dynamically are skills in Java-based web services develop- available. Security for web services is provided ment. This course is very hands-on intensive via the Secure SOAP Management. Services in nature and meant for industry practitio- listed in Fig. 5 are part of the WSRA Reference ners. Upon completion, attendees should be Implementation Release 1.0, except for those able to understand the intricacies involved in labelled in italics, which are targeted for later developing good web services and able de- release. velop robust web services. • Module 3 – WSRA Familiarisation These Core Services are accompanied by a set This module provides hands-on training on of specifications that include the Architecture the usage and application of the WSRA Requirements Specifications  and Service Core Services. It is targeted at organisations Interface Requirements Specifications . A or individuals who are interested to use the high level overview of each of the Core Service Core Services in their web service-enabled can be found in the Functional Overview docu- implementations. This course will help users ments . Presently, Release 1.0 of the Refer- of WSRA implement and use the Core Ser- ence Implementation, containing both the Core vices efficiently. Services and specifications are available for • Module 4 – Web Services Jumpstart downloads at the JSSL website, This programme aims to enable organisa- http://www.jssl.org. tions that are familiar with Java to jumpstart into web services development capability 4 WEB SERVICES CURRICULUM quickly. This is an intensive 2-week pro- gramme that is usually conducted per or- As part of JSSL’s mission, manpower develop- ganisation basis to ensure that the learning ment (that includes working professionals, stu- curve is consistent for all the participants. dents at schools and IHLs) has also been identi- Upon completion, the development team of fied as crucial to put Singapore in the global a company should be able to embark on a stage on web services. To this end, with the web service-enabled application develop- knowledge and work of WSRA as the basis, ment, including the ability to identify areas in JSSL designed and developed four training pro- an application that are suitable for web ser- grammes. Each programme is targeted at dif- vices, the best way to design the web ser- ferent skill-levels or needs and tailored accord- vices, and the interoperability and perform- ingly: ance issues that must be considered. • Module 1 – Web Services Basic This module is targeted at individuals who Module 1 and 2 are used as the basis for the are new to web services. It covers all the joint development effort with ISS where these basic technologies and components needed courses are offered to the general public by ISS. Module 3 and 4 are conducted by JSSL to identi- fied organisations. Roles & Access Phase & LC User *Service *Web Service Presentation Value-Added Management Management Personalisation Management Aggregator Transformer User Group Audit *Service *Secure SOAP Event Single Management Management Management Registry Management Handler Sign-On Common *Service Notification Sensory Digital Key XML-based Log Utility Search Tester Engine Engine Management Rules Engine *Web Service Specific Fig. 5. Layered architecture of the core services. 358 Web Services Technology for the Industry 5 CONCLUSION this is viable, JSSL also actively organises proofs-of-concept (POCs) for specific vertical This report outlined the motivation for the WSRA industry domains (such as manufacturing and framework and the context of this effort. It also logistics) that will help to validate and provide provides a high level view of the contents of the requirements for the framework. As discussed in WSRA, for both the infrastructural guidelines section 4, JSSL also uses the WSRA as the and the Reference Implementation of the Core foundation for web services curriculum devel- Services. It also provides an overview of the cur- opment with partners, where it can be used as a riculum developed within JSSL to help the Sin- platform to articulate and illustrate the creation, gapore community on its understanding and assembly and deployment of web services. knowledge of web services. Table 1. Categories of potential users. As of 31 March 2004, JSSL has successfully Category Expected Usage concluded its 2-year phase, with its objectives Independent Soft- • Guidelines/Specifications and targets successfully met. This is reflected in ware Vendors • Reference Implementation th the 5 JSSL Steering Committee held on 16 March 2004. System/Solution • Guidelines/Specifications Integrators • Reference Implementation 6 INDUSTRIAL SIGNIFICANCE • IT Framework MIS/IT depart- • Guidelines/Specifications The guidelines are meant to be used as refer- ments • Services built using the Ref- ence guides to good web service practice erence Implementation whereas the Core Services are meant to func- tion as a reference implementation, similar to • Infrastructure Guidelines the role played by the JDK in the early days of • Reference Implementation ASPs/IDCs Java development. JSSL advocates the use of Hosting alternative commercial solutions where possible. • Services Hosting However, individual vendors are encouraged to • Guidelines (good practices) enhance the Core Services and develop them Institutes of Higher Learning • Reference Implementation into commercial solutions. As part of this strat- (projects) egy, the binary codes of the Core Services are freely available for downloads. If companies have a need to access the source codes, a REFERENCES small licensing fee is applicable.  L.P. Chan and D.K. Limbu, “Adapting An IT The WSRA is intended for accelerating web ser- Infrastructure For Web Services”, version vices development as well as providing an open 1.0, March 2004, http://www.jssl.org/ platform where different players, be they small  J. Cheng, “Web Services Interoperability one-man enterprises or big companies, are able Guide”, version 2.0, Feb 2004, to have a niche in a levelled playing field. With http://www.jssl.org/ this in mind, the framework is targeted at spe-  C.H. Ang, “Web Services Testing Guide”, cific groups of potential users, including, but not version 2.0, July 2003, http://www.jssl.org/ limited to Independent Software Vendors, Sys-  P.S. Tan, “Architectural Design Specifica- tem or Solution Integrators, IT departments of tions – Reference Implementation of Core enterprises and Application Service Providers or Services”, Release 1.0, Jan 2003, Internet Data Centres (ASPs/IDCs). The Institute http://www.jssl.org/ of Higher Learning is also a potential target as  Y. Cheng and P.S. Tan, “Core Services training grounds for a web service savvy work- Interface Specifications – Reference Im- force through exposure to the WSRA and re- plementation of Core Services”, Release lated web services curriculum. 1.0, Sep 2003, http://www.jssl.org/  J. Cheng, “Core Services Functional Over- Table 1 lists some of the expected usage for view – Reference Implementation of Core these groups of potential users. For the first two Services”, Release 1.0, Jan 2003, groups, it is envisioned that the WSRA would be http://www.jssl.org/ used as a basis for developing application or industry-specific web services. To ensure that 359
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