[Recently, due to the emergence of these pages, most frequent
i was like this: "Tell me, why is it generally needed XML?
Do we have little HTML? "Without having a lot (or mind;) for the manufacture of own publications, as well as deeply charging, I preferred it is better to transfer an excellent article according to the named subj
- Perhaps this is the first episode of the series "To Help"]

JON BOSAK, TIM BRAY
XML and The Second-Generation Web
From the magazine "SCIENTFIC AMERICAN", May 1999

Give people a couple of filings, they will consemine the rest. Looking at the page where larger blocks of text are divided into smaller, all quickly understand that before them the beginning of the article. Looking at the list of grocery goods, you can quickly gues that it is "instruction" to visit the store. Seeing the speakers of numbers - to understand what is a bank account. Computers are not so smart yet - all this has to concern exactly - with what exactly they should deal with and what is required for this.

It is for this purpose - to make information itself-described - and was invented a new language markup language - Extensible Markup Language (XML). These easily across the changes ("self-described" document change the rules of communication with computers) carry huge potential in itself - the role of the Internet from the information delivery environment begins to expand on other types of human activity. And indeed, since its approval of its W3C in 1998, the XML specification with the speed of a forest fire began to penetrate everywhere - to industry and science, in the production of goods and medicine.

Enthusiasts hoped that XML would give the opportunity to solve a number of global Web problems. These problems are known: first, the Internet is a superstar network, often behaves worse than the turtle; And secondly, although there is hardly all the information in the network, it is difficult to find something necessary in it often it is difficult to rabies.

Both of these problems are mainly due to the nature of the main language of the network - HTML. And although the success of HTML compared to other ever proposed email publications is obvious, HTML is too scone: in essence, he only tells the browser, how to place on the page text, pictures and buttons on the page. HTML rests on the presentation of information, and therefore is quite simple to study, but it has to pay for it.

This is reflected in the difficulty of developing Web sites, unless these sites should resemble faxes that send pages to everyone who will ask. More than half of people and companies all over the world would prefer Web sites that can accept from users orders, send diagnoses of diseases and even run thin instrumental operations in factory workshops and scientific laboratories. Similar tasks _Nead_ did not stand in front of HTML!.

For example, even if your doctor, it turns out to "extract" in your review analyzes taken from your honeymakers, it is hardly possible to send them to another specialist to insert them back into your database. His computer does not know what to do with the information that he is as clear to him as

be Be Ba

Those words are higher that they are enclosed in angular brackets are called tags. There is no tag for analyzes in HTML, and hence the other drawback: inflexibility. Adding to the tongue of new tag is such a bureaucratic Volokhate, such a long, that no one will communicate with it. But their own tags would not prevent each program, and not just such as in the example given with the doctor.

This largely explains today's slow pace of creating online stores, mail directories and other interactive sites. By changing the number of order units and delivery method, and seeing the handful of the challenge in the "Amount" field, you still have to request a remote (already overloaded work). You will send you a back full-form page with graphics and everything else. While your own powerful computer will be idle idle because I just learned something like

and But not prices with delivery options.

Add to this and unsatisfactory quality of search options in Web. Since there is no way there is somehow especially to mark price information, it is strongly impossible to exercise in the Web searching for the price of the "price".

Something old, something new

In principle, the solution is elementary: in the tags you need to indicate what information is for information, and not how it should look. For example, place the order components on the tag shirt "price, size, quantity, color," and not "Bold, Paragraph, Row, Column", as it is offered in HTML. Then the program is easier to identify the document as an order and fulfill the rest of the work: show this order in one form or another, spend through the accounting system, or do everything so that the next new shirt will be delivered to your threshold.

We, W3C Working Group, began to launch such a project in 1996. The idea was strong, although not quite original. Throughout generations, editors and printers laundered handwritten texts for sets. A similar "markup language" developed self-intensively until 1986., As a result, as a result of the ten-year work, the International Organization for Standardization (ISO) did not introduce a system for creating new markup languages.

Having received the name SGML (Standard Generalized Markup Language), this language description language - meta language - proved its utility on the example of many major publication preparation systems. And even HTML received its definition through SGML. The only difficulty with SGML was to be in his omnivities - there is a lot of buzz things to minimize keystrokes, since at that time each byte was on the account. That is why today web browsers are not in Lada.

Creating XML, our working group cleared SGML from all the husks and suggested a strictly target and respondant metalan. The XML base is a set of rules, guided by which, each can create their own markup language. These rules are selected so that one single small program (it is also called a parser or syntactic analyzer) could cope with the recognition of any new language. Let us turn again for example with a doctor who would like to convey the tests by a specialist. If the doctors professionals were built up from XML their markup language for encoding medical records (a number of groups have long been working on a problem), then in the doctor's report to his colleague could be something like

<имя пациента> Blah Blah.
<аллергия на лекарство> BlaH Blah Blah.

In this formulation, it is no longer difficult to write a program for an arbitrarily taken computer so that it can recognize these standardized medical records and knew how to make this in the literal life of vital information into its database.

In the same way as HTML was created that any user could read Internet documents, XML gives us Esperanto, on which anyone can read and write, despite the Babylon of incompatible platforms. Yes, even from the point of view of the ordinary person in XML language, more semantic load (unlike other data formats), for it does not have something that would look like uncontamine text.

The power of the universality of XML is due to the minimum set of correctly selected rules. Firstly, the tags always make up a pair, surrounding the text to which they apply in a kind of brackets. Secondly, paired tags can be inserted into each other like quotes, allowing the complex multi-level structures.

The liner rule automatically causes the simplicity of any XML document, producing a structure known in computer science as a tree. Similar to the genealogical tree, any graphic or text element of the document is the father, son or brother (Parent, Child, Sibling) of some other element, and this relationship relationship is always definitely. Of course, trees do not describe all the diversity of data structures, but cover most of the sample applications of computers. In addition, trees are unusually convenient for programmers. There are no problems write a small piece of code to reordering transactions or output to the screen quite understandable check, when this check is represented as a tree.

The second source of the Universal Power XML is a support for a new Unicode standard - a coding system that allows interconnection of texts to all major world languages. On the contrary, in HTML, as in the mass of text processors, a document, as a rule, can only be in one particular language, no matter what - English, Japanese or Arabic.
And if the program does not know the encoding of some language, the document (in HTML) can be forgotten. It happens worse: for example, due to the inconsistency of the program encodings written in Taiwan, they often do not know how to read texts focused on mainland China. In the case of XML, if the program can work with it correctly, it will cope with any combination of encodings. Thus, XML allows you to exchange data not only between different computer platforms, but also makes it possible to overcome national and cultural barriers.

End Wide Wait)

With the distribution of the XML network should be much "responsive". Today, everything you can do computer devices on the network, it does not matter, powerful it is desktops or pocket organizers, it is no more than getting a form of "get", fill it out, then drive it to the Web server there, while working with the form will not be completed. XML gives us the opportunity to transfer the structure and semantics of data into the form, and, therefore, all these devices will be able to make the main processing in the right place and immediately. This will not only reduce the load on the server, but also should lead to a significant reduction in network traffic.

For illustration, imagine how in online travel agency you need to choose a flight from London to New York on July 4th. Most likely, you will see a list of several times longer than it can fit on the screen. This list can be reduced by setting more accurate parameters of the type of departure time, price or airline, but in this case you simply "load" the server of the travel agency for your request and are forced to wait for the answer. However, if this long list of flights were provided to you in XML, the Bureau could escort it with a small Java-applet, with which it is instantly and easily sorted and unnecessary, without resorting to any interaction with the server. Multiply it for millions of Web users, and the overall effect will be impressive.

The more network information will be charged with "sectoral" XML tags, the easier it will find what you are looking for. Today, the search on the Internet on request "work for the Exchange Broker" will flash you avalanche of advertising ads, but probably about their work there will be only a few pieces - mostly work is hiding on the free ads of newspaper advertisements, which search robots do not like to work. And now the Association of America Newspaper (Newspaper Association of America) creates its language markup on XML, promising to make the search process much more efficiently.

It doesn't matter if it's just an intermediate step. The librarians have long known ways to find something quickly - not the documents, but their compact key descriptions, only indicating the sources themselves. Namely, these are catalogs with a sample in the form of library cards. Such information about information and is called "metadata".

Therefore, from the very beginning, an important role in the XML project was given to the creation of a concomitant standard of metadata. The same role as catalog cards for library books, the February Specification of Resource Descriptions should be played for information in the Web (Resource Description Framework, RDF). Spreading over the network, RDF metadata will make the search much faster and relevant than now. There are no librarists on the network, but each webmaster, to all of the time, is committed to the easy "peerness" of his site, so we expect RDF, as soon as people will open his power, will have a huge impact on the development of the Internet.

Of course, information can be obtained without searching. In the end, the network is a hypertext - billions of pages, permeated by hyperlinks - those underlined in words, for which it is enough to click to die on some other page. In XML, the mechanism of hyperlinks is as many times reinforced. Specification of links to XML, called XLink and which W3C is preparing by the end of the year, will give the user to choose from several destination addresses. Another kind of hyperlink will allow you to get text or image right at the point of clicking, giving the opportunity to the visitor not to leave the page.

It is probably useful in XLink to be the part of the specification, which allows the authors to resort to mediated links, sending instead of the pages themselves into some kind of consolidated database. So, if the author changed the address of the page, a simple author's editing of one entry in such a database, it is easy to update all links leading to its page. This will make it possible to get rid of the "404 File Not Found" messages that are familiar with the "broken" link.

The combination of more efficient processing, more accurate search and more flexible binding revolutionizes the network structure and opens up completely new methods of access to information. For users, this new network will become significantly faster, more powerful and more useful than the network today.

Cooperation is needed

Of course, not everything is so simple. XML allows you to construct a new language to your own way, but create a good language - the task, the complexity of which should not be underestimated. Come up with a language - Only the very beginning: It is naive to expect that the values \u200b\u200bof your tags will be apparent to other people while you have not supplied the language by the manual, and will be understood by computers until you wrote programs working with language tags until you have written programs.

It is not difficult to explain why this is so. If everything you need to teach the computer to handle orders, it was reduced to the markup of the tags, then XML would not need. I would not need even programmers - the computers are smart enough to be able to do everything yourself.

What we need XML, it is not magic, but effectiveness. XML establishes the basic rules, on one layer simplifying programming details - so that people with similar interests can concentrate on another solid nuts - agreements on how they would like to make data that they want to exchange. This is a very difficult problem, although not new.

And such agreements will be, since multiplying incompatibility of computer platforms gives us as a result of the delay of the deadlines, financial losses and leads to confusion in almost all areas of activity. People want to share ideas and do the case, no matter what everyone has different computers - and that this is a reality, the interdependence of private (for different areas of activity) of languages \u200b\u200bhas a long way. However, a flurry of new abbreviations with the end of "ML" indicates a undoubtedly progressive (Inventiveness) jet that XML introduced into science, business and education.

Creating a new markup language on XML, its creators must agree on three things: what tags there will be, how they can enable each other, and how they should be processed. The first two points are a dictionary of language and structure - are encoded now by DTD (Document Type Definition). The XML standard does not oblige the language developers to resort to DTD, but most of the new DTD description languages \u200b\u200bseem to be - programmers it is so easier to write programs that understand this marking and removing something sensible from it. We also need guide kits, where the values \u200b\u200bof all tags are described in the human language. For example, HTML has a DTD description, but HTML has hundreds of the usual guides with which programmers are checked by developing browsers and other programs for Web.

Essay about style

For users, the main thing is that the program can do, and not what is written in its description. As a rule, people prefer the programs to allow them to see the information encoded in the XML language in readable form. But in the tags of the XML itself there is no special markup indicating. How data should be presented on the screen or printed sheet.

For publishers seeking to write one day, and then constantly publish ("Write OnCe and Publish Everywhere"), the most important thing is to "give birth to" publication, and then "spill" it in the myriad of the types of publications, both printed and electronic. XML helps them like this: content is placed descriptive tags independent of the visualization environment. Next, the publisher may issue the rules of representation in the form of the T.N. StyleSheets (sheets of styles), automatically "stylizing" its product for different devices and media. The standard of such an XML language, developed for these purposes, is called Extensible StyleSheet Language (XSL).

The latest browser versions can read XML documents, select the appropriate style files, and apply them to sort and format information on the screen. The reader may not even guess what is dealing with XML, not HTML, unless payments that sites with XML are freeze and easier to use.

People with vision disadvantages also receive a free winning from the XSL principles of publishing documents, since XSL gives them the opportunity to read XML in the Broaden system or from the voice. These advantages relate to the rest: for example, a community, who wants to engage in network surfing, without leaving the car, for sure it would seem quite comfortable to listen to the pages in sound accompaniment.

Although at first the kernel of the network was scientific and educational programs, today's network is already commerce (well, or can be said, commercial expectations), stocking fuel for a quick start. Everyone remembers the recent resonance caused by a splash of online sales, and is it worth talking about how businessmen interact in the network among themselves. The streams of goods of large manufacturers are still asked for automation on the network. But in today's business schemes, complex interactions of Program-to-Program are used, and in practice it works out of hand badly, for for success it is necessary for the uniformity of processing processes, which is still far away.

For centuries, people successfully engaged in business, exchanging with typical documents: orders, accounts, declarations, receipts, etc. etc. Documents worked for business, and no one demanded that one party to know the inner kitchen another. Any document was shown exactly how much the recipient had its information to show, and no more. Apparently, the exchange of documents is the most correct way to do business and in Web too. But this was not at all the task that HTML was created.

Conversely, XML is conceived precisely for the purpose of sharing the documents and it is obvious that the basis of e-commerce will rely on agreements expressed by millions of Internet-based documents running on the Internet.

Thus, the network, reinforced XML, should become for its users a quick, friendly and better place for business. Even more XML needs webmasters and Web-designers. "On the full coil" will need knowledge of new XML languages \u200b\u200bby the armies of programmers. And although the days of self-educated hackers [the authors meant the best meaning of this word] still last, the threat has already hung over their population.

Tomorrow Web-designer must be versed not only in the manufacture of text and graphics, but also in the construction of multi-level, interdependent systems based on DTD, data trees, hyperlink structures, metadata and style components - strong and advanced second-generation Web infrastructure.

In the Windows operating system, most programs store their settings in the registry. However, special files are also often used to store the application parameters, usually directly directly in directories with executable files or in subfolders. Configuration files may have different formats, including XML format, which is dedicated to this small article.

What is this xml format, what is needed and where is used

In truth, the goals with which the XML format was created (he appeared in 1996), it was possible to speak, global. XML or Extensible Markup Language, which is translated as "expandable markup language", was developed as a means of providing compatibility of transferred structured data between various software systems, especially those of them that are used on the Internet. This language is so universal that XML files understand even incompatible applications of different operating systems, which, of course, significantly simplifies the programmers to the exchange of information between software platforms.

In addition, XML is actively used when designing sites. Sometimes it is positioned as a more perfect and universal analogue of the HTML hypertext markup language, but these languages \u200b\u200bactually serve in various purposes. HTML meets mainly for displaying data, XML has also been designed to transfer and store these data. XML is also used when creating new Internet languages. By the way, familiar to many RSS used in the newsletter through news channels is based on XML.

Programs for opening and viewing files in XML format

What kind of XML format figured out, now let's see how to work with it. In truth, the need to edit XML files usually face developers and system administrators, but let's all assume that the same need arose with you. How to open the XML file? In general, you can watch it with any text editor, even notepad, but much more convenient to use special programs for these purposes.

NotePad ++.

If you are looking for how to open XML, try NotePad ++. - Universal text editor designed to create and edit code. Easy, fast and simple, it is ideal for working with all sorts of configuration files. The editor supports the syntax highlighting, a change in encoding, there is a powerful built-in search by different parameters, in one word, everything that is needed by the programmer and not only to it.

XMLPAD.

Unlike NotePad ++, XMLPAD. It is a highly specialized editor. Just as you can and need to open the XML format, since it was created for working with files of this type. In addition to viewing and editing XML documents, the XMLPAD editor supports their validation and inspection, converting to DTD, importing data from HTML and much more. As it should be, there is a syntax support in the application, there is a means of searching and replacing. Of the features of the program, you can select the presence of a built-in mini-browser to open URL links.

Those who are configured to study web languages \u200b\u200bmore seriously can be offered - advanced and at the same time simple and convenient XML editor on the Java platform. The program supports the creation and editing of XML, XSL, XSD and DTD files, there are also a built-in converter into scripts, XSLT and XQuery debugger, tools to work with XML visual diagrams and many other components. Disadvantages - the program is paid, and it does not have the support of the Russian language.

XML Marker.

Not bad way to open the XML file - use a simple editor XML Marker.. It is not so faithful as Oxygen XML Editor, but it fully copes with most tasks that arise before the user when working with XML files. In stock Representation of the tree structure of the document with the ability to quickly go to the selected rows by tags, convenient navigation, a complete set of tools for working with text data. Minus programs - no Russian language.

Browsers

There is another simplest way to read the XML file, however, we are talking about reading here. Open in Google Chrome or any other browser a new tab and drag the XML file to the browser window. The document will be represented in structured form, with the syntax highlight, everything is as it should be.

View XML files online

You can work with XML documents not only with the help of desktop programs, it is also not difficult to open an XML online. Here you note two simple online editor.

Xmlgrid.

Simply with sight, but a fairly functional online XML file editor available at XMLGrid.net. The service is supported by creating, modifying, validation and converting XML documents, there is additionally a feature of designing sites. The code of the editable file can be inserted into the web form from the clipboard, over the URL or by downloading the document to the server. The contents of the file is displayed as a table with data in which each field represents a separate cell.

XML Editor

Open the XML online file also allows an XML EDITOR Internet editor, which is part of the TutorialSpoint application set - one of the largest training resources. To use the service, go to www.tutorialspoint.com, at the top of the page, click the Tools link, find the XML Editor in the web application list and open it. You will see a simple window text editor With two columns. The left is written and edited the code, the tree structure of the document is displayed. You can download the file to the editor both from the computer and from any website, specifying the URL.