Home > Articles > Programming > Java

  • Print
  • + Share This
This chapter is from the book

Simple Object Access Protocol (SOAP)

This section looks at the history, design center, and core capabilities of SOAP as a means for establishing the base on which to build our understanding of Web services.

The Making of SOAP

Microsoft started thinking about XML-based distributed computing in 1997. The goal was to enable applications to communicate via Remote Procedure Calls (RPCs) on top of HTTP. DevelopMentor and Userland joined the discussions. The name SOAP was coined in early 1998. Things moved forward, but as the group tried to involve wider circles at Microsoft, politics stepped in and the process was stalled. The DCOM camp at the company disliked the idea of SOAP and believed that Microsoft should use its dominant position in the market to push the DCOM wire protocol via some form of HTTP tunneling instead of pursuing XML. Some XML-focused folks at Microsoft believed that the SOAP idea was good but that it had come too early. Perhaps they were looking for some of the advanced facilities that could be provided by XML Schema and Namespaces. Frustrated by the deadlock, Userland went public with a cut of the spec published as XML-RPC in the summer of 1998.

In 1999, as Microsoft was working on its version of XML Schema (XML Data) and adding support for namespaces in its XML products, the idea of SOAP gained additional momentum. It was still an XML-based RPC mechanism, however. That's why it met with resistance from the BizTalk (http://www.biztalk.org) team. The BizTalk model was based more on messaging than RPCs. It took people a few months to resolve their differences. SOAP 0.9 appeared for public review on September 13, 1999. It was submitted to the IETF as an Internet public draft. With few changes, in December 1999, SOAP 1.0 came to life.

On May 8, 2000 SOAP 1.1 was submitted as a Note to the World Wide Web Consortium (W3C) with IBM as a co-author—an unexpected and refreshing change. In addition, the SOAP 1.1 spec was much more extensible, eliminating concerns that backing SOAP implied backing some Microsoft proprietary technology. This change, and the fact that IBM immediately released a Java SOAP implementation that was subsequently donated to the Apache XML Project (http://xml.apache.org) for open-source development, convinced even the greatest skeptics that SOAP is something to pay attention to. Sun voiced support for SOAP and started work on integrating Web services into the J2EE platform. Not long after, many vendors and open-source projects were working on Web service implementations.

Right before the XTech 2000 Conference, the W3C made an announcement that it was looking into starting an activity in the area of XML protocols: "We've been under pressure from many sources, including the advisory board, to address the threat of fragmentation of and investigate the exciting opportunities in the area of XML protocols. It makes sense to address this now because the technology is still early in its evolution..." (http://lists.w3.org/Archives/Public/xml-dist-app/2000Feb/0006.html). On September 13, 2000 the XML Protocol working group at the W3C was formed to design the core XML protocol that was to become the core of XML-based distributed computing in the years to come. The group started with SOAP 1.1 as a foundation and produced the first working draft of SOAP 1.2 on July 9, 2001.

What Should SOAP Do?

SOAP claims to be a specification for a ubiquitous XML distributed computing infrastructure. It's a nice buzzword-compliant phrase, but what does it mean? Let's parse it bit by bit to find out what SOAP should do.

XML means that, as a second-generation XML protocol, SOAP is based on XML 1.0, XML Schema, and XML Namespaces.

Distributed computing implies that SOAP can be used to enable the interoperability of remote applications (in a very broad sense of the phrase). Distributed computing is a fuzzy term and it means different things to different people and in different situations. Here are some "facets" you can use to think about a particular distributed computing scenario: the protocol stack used for communication, connection management, security, transaction support, marshalling and unmarshalling of data, protocol evolution and version management, error handling, audit trails, and so on. The requirements for different facets will vary between scenarios. For example, a stock ticker service that continuously distributes stock prices to a number of subscribers will have different needs than an e-commerce payment-processing service. The stock ticker service will probably need no support for transactions and only minimal, if any, security or audit trails (it distributes publicly available data). The e-commerce payment-processing service will require Cerberean security, heavy-duty transaction support, and full audit trails.

Infrastructure implies that SOAP is aimed at low-level distributed systems developers, not developers of application/business logic or business users. Infrastructure products such as application servers become "SOAP enabled" by including a Web service engine that understands SOAP. SOAP works behind the scenes making sure your applications can interoperate without your having to worry too much about it.

Ubiquitous means omnipresent, universal. On first look, it seems to be a meaningless term, thrown into the phrase to make it sound grander. It turns out, however, that this is the most important part. The ubiquity goal of SOAP is a blessing because, if SOAP-enabled systems are everywhere on the Internet, it should be easier to do distributed computing. After all, that's what SOAP is all about. However, the ubiquity of SOAP is also a curse, because one technology specification should be able to support many different types of distributed computing scenarios, from the stock ticker service to the e-commerce payment-processing service. To meet this goal, SOAP needs to be a highly abstract and flexible technology. However, the more abstract SOAP becomes, the less support it will provide for specific distributed computing scenarios. Furthermore, greater abstraction means more risk that different SOAP implementations will fail to interoperate. This is the eternal tug-of-war between generality and specificity.

What Is SOAP, Really?

Like most new technologies that change the rules of how applications are being developed, Web services and SOAP have sometimes been over-hyped. Despite the hype, however, SOAP is still of great importance because it is the industry's best effort to date to standardize on the infrastructure technology for cross-platform XML distributed computing.

Above all, SOAP is relatively simple. Historically, simplicity is a key feature of most successful architectures that have achieved mass adoption. The Web with HTTP and HTML at its core is a prime example. Simple systems are easier to describe, understand, implement, test, maintain, and evolve. At its heart, SOAP is a specification for a simple yet flexible second-generation XML protocol. SOAP 1.0 printed at about 40 pages. The text of the specification has grown since then (the authors have to make sure the specification is clear and has no holes), but the core concepts remain simple.

Because SOAP is focused on the common aspects of all distributed computing scenarios, it provides the following:

  • A mechanism for defining the unit of communication. In SOAP, all information is packaged in a clearly identifiable SOAP message. This is done via a SOAP envelope that encloses all other information. A message can have a body in which potentially arbitrary XML can be used. It can also have any number of headers that encapsulate information outside the body of the message.

  • A mechanism for error handling that can identify the source and cause of the error and allows for error-diagnostic information to be exchanged between participants of an interaction. This is done via the notion of a SOAP fault.

  • An extensibility mechanism so that evolution is not hindered and there is no lock-in. XML, schemas, and namespaces really shine here. The two key requirements on extensions are that they can be orthogonal to other extensions and they can be introduced and used without the need for centralized registration or coordination. Typically, extensions are introduced via SOAP headers. They can be used to build more complex protocols on top of SOAP.

  • A flexible mechanism for data representation that allows for the exchange of data already serialized in some format (text, XML, and so on) as well as a convention for representing abstract data structures such as programming language datatypes in an XML format.

  • A convention for representing Remote Procedure Calls (RPCs) and responses as SOAP messages, because RPCs are the most common type of distributed computing interaction and because they map so well to procedural programming language constructs.

  • A document-centric approach to reflect more natural document exchange models for business interactions. This is needed to support the cases in which RPCs result in interfaces that are too fine grained and, therefore, brittle.

  • A binding mechanism for SOAP messages to HTTP, because HTTP is the most common communication protocol on the Internet.

Although solid consensus exists in the industry about the core capabilities of SOAP, there is considerably less agreement on how higher-level issues such as security and transaction-management should be addressed. Nearly everyone agrees that to tackle the broad spectrum of interesting problems we are faced with, we need to work in parallel on a set of layered specifications for XML distributed computing. Indeed, many loosely coupled industry initiatives are developing standards and technologies around SOAP. Tracking these efforts is like trying to shoot at many moving targets. The authors of this book have tried our best to address the relevant efforts in this space and to provide you with up-to-date information. Chapter 1 showed how many of these efforts layered around the notion of the Web services interoperability stack. Chapter 5, "Using SOAP for e-Business," goes into more detail about the set of standards surrounding SOAP that enable secure, robust, and scalable enterprise-grade Web services.

Now, let's take a look at how SkatesTown is planning to use SOAP and Web services.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020