In the end, the Working Group realizes that a common foundation is needed for building additional layers like security, routing, choreography, and so forth see the GXA specs for more examples but at the same time, they don't want to discourage experimentation and research. I suppose the Working Group's definition leaves the door open for such ideas. One of the WS-I's main goals is to "articulate and promote a common industry vision for Web services The WS-I complements the W3C because it's more focused on practical issues like providing implementation guidelines.
A XML Schema defines two validation techniques that can be used by processors: lax and strict. Lax validation means that the processor should validate if schema information is available, while strict validation means that the processor must validate or produce an error if schema information is not available. For example, when using wildcards xsd:any , XML Schema allows you to specify which form of validation you'd like the processor to use:.
The following XML document contains a person element, which may or may not be valid, according to the previous schema:. When the processor validates this instance, it will first look for the appropriate schema information like the complexType that describes the skillSet element. If it's able to locate the schema information, it will continue performing validation on skillSet's structure; otherwise it will skip the element and assume it's valid note: in addition to strict and lax, you can also specify "skip," which tells the processor not to validate the given element.
Wildcards, however, only apply to local elements. But what about the root element? Unfortunately, XML Schema doesn't provide a way to specify or constrain what's allowed as the root element of a document. In other words, the root element of a document can be any global element in the schema. If there were such a declaration, it could allow you to specify whether to use lax or strict like wildcards , and if you specified strict, you wouldn't run into what you're experiencing. XML Schema chose a different approach.
If the processor cannot locate schema information for the root element, it assumes that the element is of type ur-type or anyType. I agree that it can be misleading when the processor tells you an instance is valid when, in fact, it didn't really analyze the structure of the element. This will always be the case if the schema's targetNamespace doesn't match the namespace of the root element in the instance document I see this bug all the time.
It's possible to catch this issue if you're willing to write a little code. See Figure 9 for a simple example. If you're writing code using the. NET Framework with System. Xml, you have to do a little more. You'll need to wrap an XmlValidatingReader around the instance document, load the schema into the XmlValidatingReader's schema cache see the Schemas property , and then explicitly move the cursor to the root element by calling MoveToContent.
Once positioned on the root element, the SchemaType property provides access to its XML Schema type definition if found. Hence, if SchemaType is null, you know it didn't locate the correct schema and, therefore, didn't perform validation. Figure 10 provides a complete example. Q Should I use DateTime. Parse, Convert. ToDateTime, or XmlConvert. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode.
Is this page helpful? Please rate your experience Yes No. Any additional feedback? Submit and view feedback for This product This page. View all page feedback. In this article. When you are finished, you will be ready to move on and create more complex services and utilize the advanced techniques outlined in "Sams Teach Yourself. NET in 24 Hours. XML Web services represent an exciting new tool in software creation, and this first hour will introduce you to the technologies and tools behind it.
You will become familiar with the protocols used in the XML Web services model, and you will also learn about the. An XML Web service is simply a unit of programming functionality that is exposed to client applications via the Internet. In the past, developers started to move away from the "all in one" style of development, in which all of an application's functionality was contained in one code module.
Developers began to move code into objects, called components, which existed outside of the initial project. These components could be updated independently of each other and the main program, thus making for smaller and more efficient tasks. With code now being developed from these component building blocks, it became easier to build a project in teams and to reuse code. Components from one project could be combined with new components to form different applications.
It wasn't long before third-party companies began selling components to software developers for use in their own projects. With the rise of networking and technologies such as DCOM, developers also began to move these components onto different machines across the network. This gave users access to great processing power, via the distribution of tasks to varying machines, and it gave developers the ability to change one component and simultaneously affect all users.
Now, with XML Web services, you have the ability to distribute your application across not only a network but also the Internet. Components can be built and hosted anywhere in the world and consumed by other components. Third-party companies no longer just create and sell components; they host them as well. For a small example, think of a DLL or function library that contains spell-checking software.
If you were writing several applications to handle your company's word processing and e-mail capabilities, you would want to add this component into all of your applications.
Now, if someone created this spell-checking component as a Web service, you could simply use that component in all of your applications. They would all simultaneously have access to the expanded word list. One of the most important factors in the future of XML Web services technology is its role in creating platform-neutral systems.
This is true even for systems that are not running the. NET platform. In Hour 9, you will see some examples of clients that are built on non-. NET platforms. However, XML Web services built on. NET platforms will not be covered in this book.
XML Web services help create platform-neutral systems by using the same set of standards as the Internet. When the request is processed, another XML document is generated, this one containing any requested data, and sent back to the client application. The road to XML Web services has been a long one. The introduction of these object design technologies allowed developers to build programs in smaller components and allowed these components to be reused in other programs.
From COM sprang DCOM and other, similar technologies that allowed these components to be moved off the user's machine and onto servers. This allowed components to be simultaneously used by multiple users and multiple applications. The rise of the Internet and Internet-enabled applications took the concept of distributing applications one step further by allowing components to be called by Web applications written in ASP or CGI and being used all over the world.
Since the rise of the Internet, developers have searched for better ways to expose functionality and services to their user community. ASP, briefly mentioned above, was another big step in the move toward more distributed applications. ASP provided a much easier method of development, used a commonly known language, and also provided a rich set of built-in objects to help developers quickly put together applications.
Finally, developers had a standard way in which to describe data and services. From there it was not long before someone, actually several someones, began to write applications that communicated with each other by passing XML documents. These were the first Web services. As you were reading about XML Web services' role in creating platform-independent applications and their use of HTTP protocols to communicate with other applications, you probably noticed the need for a standard format in which clients can actually send requested data, such as method calls with parameters, and receive Web service data, such as strings, arrays, and record sets.
Well, that formatting issue was solved with XML. SOAP documents are simply a way of marking up a call to an XML Web service method or function, including all of its required arguments. SOAP is also used to mark up all of the returned results so that the client can understand what is being sent back to it.
Data is marked up with XML tags denoting the type of data being sent back, such as string or long, and the variable name to which the data was sent, in the case of parameters. This helps XML Web services and their client applications maintain type safety even across differing platforms. When you develop an XML Web service, you will generate more than just the code that provides the functionality you wish to expose. You will also be creating a host of files, and in the case of UDDI, entries in existing files that will help support your service and describe it to the intended user community.
Some of the files that you will create or edit when working with Web services are. NET application files. These are files that are created either by you using a simple text editor or, if you are using Visual Studios. This is the global file of your XML Web services. This file handles application-level events such as requests and sessions, both of which you will learn more about as you progress through this book. XML is also used to help prospective users find a given Web service.
Disco files, short for discovery files, are created and exposed to the Internet as the primary way of advertising a service.
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