. xml version="" encoding="UTF-8"?> Belgian Waffles $ Two of our famous ."/>
 
    Contents
  1. XML Tutorial
  2. XML - Wikipedia
  3. XML basics for new users

This tutorial will teach you the basics of XML. The tutorial is divided into sections such as. XML Basics, Advanced XML, and XML tools. Each of these sections. XML for Beginners „XML is the cure for your data exchange, information integration pdf">. xml version="" encoding="UTF-8"?> Belgian Waffles $ Two of our famous .

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Xml Basics Pdf

Using XPath to Navigate an XML Document Now that you've learned the basics of DTD construction and the right way to define elements, attributes, and. An XML document is well-formed, if – it complies with the rules on the previous page. – i.e. it can be parsed by an XML parser without error. ▫ An XML. The following example is a note to Tove, from Jani, stored as XML: .. If you want to learn more about XSLT, please read our XSLT Tutorial. 8. XML.

Applications for the Microsoft. Many of these standards are quite complex and it is not uncommon for a specification to comprise several thousand pages. XML is used extensively to underpin various publishing formats. Disparate systems communicate with each other by exchanging XML messages. This is also referred to as the canonical schema. XML has come into common use for the interchange of data over the Internet. This is not an exhaustive list of all the constructs that appear in XML; it provides an introduction to the key constructs most often encountered in day-to-day use. Character An XML document is a string of characters. Almost every legal Unicode character may appear in an XML document. Processor and application The processor analyzes the markup and passes structured information to an application. The specification places requirements on what an XML processor must do and not do, but the application is outside its scope. The processor as the specification calls it is often referred to colloquially as an XML parser. Markup and content The characters making up an XML document are divided into markup and content, which may be distinguished by the application of simple syntactic rules. Strings of characters that are not markup are content.

Needless to say, computers are really bad at this game, which is a shame, as many computing tasks require semantic skill. However, even a cursory glance at the rest of the document reveals some very human errors. This last product listing also displays a price before the description, and the price is italicized instead of appearing in bold.

The computer would be able only to render the document to a browser with the styles associated with each tag. Notice that this new document contains absolutely no information about display. Essentially, XML allows you to separate information from presentation — just one of its many powerful abilities. In the example above, we know that a product listing contains products, and that each product has a name, a description, a price, and a shipping cost.

You could say, rightly, that each XML document is self-describing , and is readable by both humans and software. Now, everyone makes mistakes, and XML programmers are no exception. To ensure that everyone plays by the rules, you need a DTD a document type definition , or schema.

Once you have a DTD in place, anyone who creates product listings for your application will have to follow the rules. I want to examine the contents of a typical XML file, character by character. The simplest XML elements contain an opening tag, a closing tag, and some content.

In XML, content is usually parsed character data. Following the content is the closing tag, which exhibits the same spelling and capitalization as your opening tag, but with one tiny change: If you use attributes on any elements, then attribute values must be single- or double-quoted.

No longer can you get by with bare attribute values like you did in HTML! The following is okay in HTML:. Also, if you nest your elements improperly i. In XML, this improper nesting of elements would cause the program reading the document to raise an error. As XML allows you to create any language you want, the inventors of XML had to institute a special rule, which happens to be closely related to the proper nesting rule. This is called an attribute.

You can think of attributes as adjectives — they provide additional information about the element that may not make any sense as content. What information should be contained in an attribute? What should appear between the tags of an element? Some developers including me! Another common rule of thumb is to consider the length of the data.

Potentially large data should be placed inside a tag; shorter data can be placed in an attribute. In other parts of our DVD listing, the information seems a little bare. One way to do so is with the addition of attributes:. It would be smarter, from an architectural point of view, to have a separate listing of actors with unique IDs to which you could link.

Some XML elements are said to be empty — they contain no content whatsoever. Familiar examples are the img and br elements in HTML. Remember that in XML all opening tags must be matched by a closing tag. For empty elements, you can use a single empty-element tag to replace this:. I mentioned entities earlier. An entity is a handy construct that, at its simplest, allows you to define special characters for insertion into your documents.

XML, true to its extensible nature, allows you to create your own entities. What a time-saver! XML documents are more then just a sequence of elements. This feature, combined with all that content encapsulated in opening and closing tags, takes all XML documents far past the realm of mere data and into the revered halls of information. Data can comprise a string of characters or numbers, such as But the only way to turn this data into information and therefore make it useful is to add context to it — once you have context, you can be sure about what the data represents.

When you take into account the second point — that an XML document is really a hierarchy of objects — all sorts of possibilities open up.

Remember what we discussed before — that, in an XML document, one element contains all the others? Well, that root element becomes the root of our hierarchical tree. You can think of that tree as a family tree, with the root element having various children in this case, product elements , and each of those having various children name, description, and so on. In turn, each product element has various siblings other product elements and a parent the root , as shown in Figure 1.

Because what we have is a tree, we should be able to travel up and down it, and from side to side, with relative ease. Before, we talked about transforming data into information by adding context. Earlier in this chapter, I made a point about XML allowing you to separate information from presentation. For example, if you stored your information in a word processing program, it would contain all kinds of information about the way it should appear on the printed page — lots of bolding, font sizes, and tables.

Unfortunately, if that document also had to be posted to the Web as an HTML document, someone would have to convert it either manually or via software , clean it up, and test it. If yet another person wanted to take the same information and use it in a slide presentation, they might run the risk of using outdated information from the HTML version.

As you can see, it can get pretty messy! If you made changes to the XML file, the other files would also change automatically once you passed the XML file through the process. This notion, by the way, is an essential component of single-sourcing — i. As you can see, separating information from presentation makes your XML documents reusable, and can save hassles and headaches in environments in which a lot of information needs to be stored, processed, handled, and exchanged.

That means the publisher can generate sample PDFs for its Website, make print-ready files for the printer, and potentially create ebooks in the future. All formats will be generated from the same source, and all will be created using different style sheets to process the base XML files.

One of the most powerful advantages of XML, of course, is that it allows you to define your own language. However, this most powerful feature also exposes a great weakness of XML. If all of us start defining our own languages, we run the risk of being unable to understand anything anyone else says. A valid document, then, is nothing more then a well-formed document that adheres to its DTD.

For the most part, you will only care that your documents are well formed. Well-formedness alone allows you to create ad hoc XML documents that can be generated, added to an application, and tested quickly.

The first thing we want to do is to create an XML document. If you have Internet Explorer 5 or higher installed on your machine, you can view your newly-created XML file.

As Figure 1.

Notice the little minus signs next to some of the XML nodes? A minus sign in front of a node indicates that the node contains other nodes.

If you click the minus sign, Internet Explorer will collapse all the child nodes belonging to that node, as shown in Figure 1. Figure 1. Collapsing nodes displaying in Internet Explorer. View larger image. The little plus sign next to the first product node indicates that the node has children.

Clicking on the plus sign will expand any nodes under that particular node. In this way, you can easily display the parts of the document on which you want to focus. Now, open your XML document in any text editing tool and scroll down to the cost node of the second product.

Save your work and reload Internet Explorer. You should see an error message that looks like the one pictured in Figure 1. As you can see, Internet Explorer provides a rather verbose explanation of the error it ran into: Furthermore, it provides a nice visual of the offending line, a little arrow pointing to the spot at which the parser thinks the problem arose. Even though the problem is really with the start tag, the arrow points to the end tag.

Because Internet Explorer uses a non-validating parser by default remember, this means it only cares about well-formedness rules , it runs into problems at the end tag. You now have to backtrack to find out why that particular end tag caused such a problem.

Open your XML document in an editor once more, and fix the problem we introduced above. Save your work and reload your browser. You should see an error message similar to the one shown in Figure 1. At first glance, this error message seems a bit more obscure than the previous one. However, look closely and what do you see? Firefox is a popular open-source browser, and at the time this book went to print the latest version was 1.

XML Tutorial

You can download a free copy from the Mozilla website. Okay, so both Internet Explorer and Firefox will check your XML for well-formedness, but you need to know for future reference how to check that an XML file is valid i.

How do you do that? There are various well-known online validating XML parsers. All you have to do is visit the appropriate page, upload your document, and the parser will validate it. Here is the most popular online parser.

Sometimes, it may be impractical to use a Website to validate your XML because of issues relating to connectivity, privacy, or security. This checks for well-formedness if the document has no DTD, and for well-formedness and validity if a DTD is specified. Results of the validation will appear under the Results area, as illustrated in Figure 1. For most purposes, an online resource will do the job nicely. If you work in a company that has an established software development group, chances are that one of the XML-savvy developers has already set up a good validating parser.

This project will help ground your skills as you obtain firsthand experience with practical XML development techniques, issues, and processes. It usually consists of the following components:. Before you build any kind of CMS, first you must gather information that defines the basic requirements for the project.

The goal of the CMS is to make things easier for those who need to develop and run the site. And making things easier means having to do more homework beforehand! Although you may groan at the thought of this kind of exercise, a set of well-defined requirements can make the project run a lot more smoothly. What kind of requirements do we need to gather? Essentially, requirements fall into three major categories: In the world of XML, each of these different types of content is, naturally enough, called a document type.

You also have to know how each of these content types will break out into its separate components, or metadata. Each article, for instance, will have various pieces of metadata, such as a headline, author name, and keywords, each of which the CMS needs to track. The final challenge — to define various types of metadata — can be a blessing in disguise. In my experience, once people grasp the importance of metadata, they race off in every direction and collect every single piece of metadata they can find about a given content type.

For example, the client might start to track the date on which an article is first drafted. Gathering metadata can be very tricky. At first glance, we could say that all of our articles should contain elements for author name and email address, and leave it at that. However, we may later decide that we want site visitors to search or browse articles by author. In this case, it would make more sense to have a centralized list of authors, each with his or her own unique ID.

Having a separate author listing would also allow us to easily set bylines for each author, in case someone decided they wanted to publish pieces under a pen name. It would also allow us to track author information across content types. Of course, agreeing on this approach means that we need to do other work later on, such as building administrative interfaces for author listings.

The other two are site functionality and site design. Every piece of metadata could potentially drive some kind of site behavior, but each piece of metadata also must be managed by the administration tools you set up. Site behavior should always be based on and driven by metadata.

Typical site behavior for a CMS-powered Website includes browsing by content categories, browsing by author, searching on titles and keywords, dynamic news sidebars, and more. Additionally, many XML- and database-powered sites feature homepages that boast dynamically updated content, such as Top Ten Downloads, latest news headlines, and so on.

Our CMS will need to have an administrative component for each content type. It will also have to administer pieces of information that have nothing to do with content types, such as which users are authorized to log in to the CMS, and the privileges each of them has. It goes without saying that your administrative interface has to be secure, otherwise, anyone could click to your CMS and start deleting content, making unauthorized changes to existing content, or adding new content that you may not want to have on your site.

A workflow is simply a set of rules that allow you to define who does what, when, and how. For example, your workflow might stipulate that a user with writer privileges may create an article, but that only a production editor can approve that content for publication on the site.

In many cases, CMS workflows emulate actual workflows that exist in publication and marketing departments. We want to publish articles and news stories on our site.

We definitely want to keep track of authors and site administrators, and we also want to build a search engine. Whenever I build an XML-powered application, I try to define the content types first, because I find that all the other elements cascade from there. The articles in our CMS will be the mainstay of our site. In addition to the article text, each of our articles will be endowed with the following pieces of metadata:.

Furthermore, because we need to identify each article in our system uniquely with an ID of some sort, it makes sense to add an id attribute to the root element that will contain this value. A unique identifier will ensure that no mistakes occur when we try to edit, delete, or view an existing article. Now, each of our articles will have an author, so we need to reserve a spot for that information.

Our article will need a headline, a short description, a publication date, and some keywords. The keyword listing can be handled in one of two ways. This approach will satisfy the structure nuts out there, but it turns out to be too complicated for the way we will eventually use these keywords. We also need to track status information on the article.

However, you probably already see that status is very similar to keyword listings in that it has the potential to belong to many different content types. As such, it makes sense to centralize this information. As most of our content will be displayed in a Web browser, it makes sense to use as many tags as possible that a browser like IE or Firefox can already understand.

But for the purposes of our article storage system, we want to treat all of the HTML tags and text that make up the document body as a simple text string, rather than having to handle every single HTML tag that could appear in the article body. My goal for that chapter was to show you how flexible XML really is. It is both a style sheet specification and a kind of programming language that allows you to transform an XML document into the format of your choice: XPath is a language for locating and processing nodes in an XML document.

Because each XML document is, by definition, a hierarchical structure, it becomes possible to navigate this structure in a logical, formal way i.

A document type definition DTD is a set of rules that governs the order in which your elements can be used, and the kind of information each can contain.

While a DTD can provide only general control over element ordering and containment, schemas are a lot more specific. They can, for example, allow elements to appear only a certain number of times, or require that elements contain specific types of data such as dates and numbers. Both technologies allow you to set rules for the contents of your XML documents. If you need to share your XML documents with another group, or you must rely on receiving well-formed XML from someone else, these technologies can help ensure that your particular set of rules is properly followed.

The ability of XML to allow you to define your own elements provides flexibility and scope. Now, open your XML document in any text editing tool and scroll down to the cost node of the second product.

You should see an error message that looks like the one pictured in Figure 1. Error message displaying in Internet Explorer. Furthermore, it provides a nice visual of the offending line, a little arrow pointing to the spot at which the parser thinks the problem arose. Because Internet Explorer uses a non-validating parser by default remember, this means it only cares about well-formedness rules , it runs into problems at the end tag.

You now have to backtrack to find out why that particular end tag caused such a problem. Open your XML document in an editor once more, and fix the problem we introduced above. Save your work and reload your browser. You should see an error message similar to the one shown in Figure 1.

XML - Wikipedia

Debugging a more complex error. At first glance, this error message seems a bit more obscure than the previous one. However, look closely and what do you see? Firefox is a popular open-source browser, and at the time this book went to print the latest version was 1. You can download a free copy from the Mozilla website. How do you do that?

Well, there are a couple of options, listed below. All you have to do is visit the appropriate page, upload your document, and the parser will validate it. Here is the most popular online parser. Viewing raw XML in Firefox. Using a Local Validating Parser Sometimes, it may be impractical to use a Website to validate your XML because of issues relating to connectivity, privacy, or security. Just download the package and install it by following the instructions provided. Be warned, however, that you will have to know something about working with Java tools and files before you can get this one installed successfully.

This checks for well-formedness if the document has no DTD, and for well-formedness and validity if a DTD is specified. Results of the validation will appear under the Results area, as illustrated in Figure 1. For most purposes, an online resource will do the job nicely. If you work in a company that has an established software development group, chances are that one of the XML-savvy developers has already set up a good validating parser.

This project will help ground your skills as you obtain firsthand experience with practical XML development techniques, issues, and processes. It usually consists of the following components: A data back-end comprising XML or database tables that contains all your articles, news stories, images, and other content.

A data display component — usually templates or other pages — onto which your articles, images, etc. A data administration component. This usually comprises easy-to-use HTML forms that allow site administrators to create, edit, publish, and delete articles in some kind of secure workflow. Requirements Gathering Before you build any kind of CMS, first you must gather information that defines the basic requirements for the project. The goal of the CMS is to make things easier for those who need to develop and run the site.

And making things easier means having to do more homework beforehand! Although you may groan at the thought of this kind of exercise, a set of well-defined requirements can make the project run a lot more smoothly. What kind of requirements do we need to gather? Essentially, requirements fall into three major categories: What kind of content will the CMS handle? How is each type of content broken down? Who will be visiting the site, and what behaviors do these users expect to find? For example, will they want to browse a hierarchical list of articles, search for articles by keyword, see links to related articles, or all three?

What do the site administrators need to do? For example, they may need to log in securely, create content, edit content, publish content, and delete content. If your CMS will provide different roles for administrative users — such as site administrators, editors, and writers — your system will become more complex.

In the world of XML, each of these different types of content is, naturally enough, called a document type. Here it is again, with a few more nodes added to it: Example 1. It really is as good as we say it is--or your money back. As Figure 1. Notice the little minus signs next to some of the XML nodes?

A minus sign in front of a node indicates that the node contains other nodes. If you click the minus sign, Internet Explorer will collapse all the child nodes belonging to that node, as shown in Figure 1.

Collapsing nodes displaying in Internet Explorer. View larger image. The little plus sign next to the first product node indicates that the node has children. Clicking on the plus sign will expand any nodes under that particular node.

In this way, you can easily display the parts of the document on which you want to focus. Now, open your XML document in any text editing tool and scroll down to the cost node of the second product. You should see an error message that looks like the one pictured in Figure 1. Error message displaying in Internet Explorer. Furthermore, it provides a nice visual of the offending line, a little arrow pointing to the spot at which the parser thinks the problem arose.

Because Internet Explorer uses a non-validating parser by default remember, this means it only cares about well-formedness rules , it runs into problems at the end tag. You now have to backtrack to find out why that particular end tag caused such a problem.

Open your XML document in an editor once more, and fix the problem we introduced above. Save your work and reload your browser. You should see an error message similar to the one shown in Figure 1. Debugging a more complex error. At first glance, this error message seems a bit more obscure than the previous one.

However, look closely and what do you see? Firefox is a popular open-source browser, and at the time this book went to print the latest version was 1. You can download a free copy from the Mozilla website.

How do you do that? Well, there are a couple of options, listed below. All you have to do is visit the appropriate page, upload your document, and the parser will validate it.

Here is the most popular online parser. Viewing raw XML in Firefox. Using a Local Validating Parser Sometimes, it may be impractical to use a Website to validate your XML because of issues relating to connectivity, privacy, or security. Just download the package and install it by following the instructions provided.

Be warned, however, that you will have to know something about working with Java tools and files before you can get this one installed successfully. This checks for well-formedness if the document has no DTD, and for well-formedness and validity if a DTD is specified. Results of the validation will appear under the Results area, as illustrated in Figure 1. For most purposes, an online resource will do the job nicely. If you work in a company that has an established software development group, chances are that one of the XML-savvy developers has already set up a good validating parser.

This project will help ground your skills as you obtain firsthand experience with practical XML development techniques, issues, and processes. It usually consists of the following components: A data back-end comprising XML or database tables that contains all your articles, news stories, images, and other content.

XML basics for new users

A data display component — usually templates or other pages — onto which your articles, images, etc. A data administration component. This usually comprises easy-to-use HTML forms that allow site administrators to create, edit, publish, and delete articles in some kind of secure workflow. Requirements Gathering Before you build any kind of CMS, first you must gather information that defines the basic requirements for the project. The goal of the CMS is to make things easier for those who need to develop and run the site.

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