Quite often, many users of modern computer systems and software products of various types come across files with the .xml extension. Many people simply have no idea what kind of document it is, how to open it. Now it will be considered, at the same time we will find out what it is and what it is for.

What is an XML file

Let's start with the fact that, from the point of view of modern computer technologies and programs used to create documents of this type, it is a text file in which the commands of the Extensible Markup Language are written, which quite closely resembles the well-known markup tool HTML.

As a rule, an XML file contains general information about an object, which is expressed in descriptive means (more on this later). As for the data stored in such containers, these can be databases often used for video and audio catalogs on the Internet, saved user settings of programs and applications, as well as entire web pages.

As an example, let's take, say, an audio album of some artist. The XML file includes information about the release year, genre, number and names of tracks, popularity, etc. However, when visiting resources on the World Wide Web, a surfer does not need to think about physically opening such an information file, since even when playing a song online in a player all data type will be displayed as contained in standard MP3 files as ID3 tags. The information is, as it were, loaded to the track being played.

XML file view

If you look at the view of the file, you can immediately notice that the properties of any object are described in it using tags and attributes that are set manually.

We are not talking about the main commands of the language itself, since an ordinary user does not need such information. The only thing that can be noted is that a certain number of elements used to describe an object in this format does not exist: as many are needed, as many are set.

How to open standard XML format

Now let's see how to open an XML file. As already, probably, many have understood, this is a text file, which means that it is easiest to use any, even the most primitive, editor to view or edit it. Yes, even the same "Notepad" from the standard Windows set.

However, not everything is so simple here. The fact is that by double-clicking the file without setting the appropriate association with any program, it will not open. In the best case, the system will offer a list of the most suitable applications. You can choose the program of your choice, and at the same time put a tick in front of the item for permanent use of the selected application for all files of this type.

You can do differently by right-clicking on the file and then choosing the "Open with ..." command, after which, again, select the required application either from the list, or specify the location of the main executable component (most often it is an EXE file).

The third way to open the XML file is to first start the program and then use the open file menu (in most cases, this is Ctrl + O). In this case, it is completely unnecessary to use Notepad. Please, the file opens without any problems in the same Word application and the like. Even Microsoft Excel is capable of opening data in this format.

However, if it becomes necessary to edit the XML format, then it is better to use professional utilities with support for language syntax, for example, Oxygen XML Editor, XML Marker or EditiX Lite Version. Naturally, these are not all utilities capable of working with the file language at the highest level. Today there are a lot of such programs.

Now a few words about why the XML file sometimes gets an error when opening. Most often this is due to a violation of the integrity of the file itself, as well as incorrect introduction of descriptive attributes or tags. In addition, Excel has a limit on the number of rows displayed, so the data may be incomplete when opened.

Possible errors when opening an XML file as an email attachment

Sometimes errors can appear when an attempt is made to open a file that is an attachment to an email message. This most often applies to standard email clients like Outlook Express.

The fact is that at first the attachment is saved in the form of temporary data (very often with the addition of an additional .tmp to the main extension), and the call is made to it.

To avoid such a situation, it is enough to simply initially save the attachment in its original format to any convenient place on disk or on removable media, and then use the standard methods described above.

Instead of a total

As you can see, there is nothing difficult in understanding the structure and methods of opening files of this format. Here, however, the issue of creating XML data was not fundamentally considered, since in order to fully understand the process, you need to know at least the basics of the language itself. As for the rest, it seems that users will not have any difficulties with files of this format.

XML is used in many aspects of web development, but its main purpose is to make it easier to store and transfer data.

XML separates data from HTML

If you need to display dynamic data in an HTML document, it will take too long if, whenever this data has changed, you edit the HTML document itself.

WITH XML data can be stored in separate XML files. In doing so, you focus on using HTML / CSS for display and templating, and you can be sure that the incoming new data does not require any changes in the HTML code of the document.

XML simplifies data distribution

In the real world, computer systems and databases use data in incompatible formats.

XML data is stored in plain text format. This provides software and hardware independence.

This makes it easy to create data that can be used by a wide variety of applications.

XML makes data transfer easy

One of the most time-consuming problems of developers has always been and still remains the problem of data exchange between incompatible systems.

Passing data in XML significantly reduces the complexity of this problem, since data in this format can be read by different incompatible applications.

XML makes it easy to modify the platform

Moving to new systems (hardware or software platforms) always takes a long time. A lot of data needs to be converted to new formats. In this case, often incompatible data is lost.

XML data is stored in text format. This makes it much easier to expand or upgrade operating systems, migrate to new applications or browsers without the risk of losing data.

XML makes your data more accessible

Your data can be accessed not only by HTML documents, but also by any other application.

XML makes your data available to all kinds of "reading machines" (voice machines, news feeds, etc.), making it much easier for people with visual impairments and other physical problems to access it.

XML is used to create new Internet languages

Many programming languages ​​on the Internet have been created using XML.

Here are some examples:

• XHTML
• WSDL for describing available web services
• WAP and WML as markup languages ​​for handheld devices such as PDAs
• RSS languages ​​for news feeds
• RDF and OWL for resource description and ontology
• SMIL for describing multimedia for the web

Extensible Markup Language (XML). They are really just text files that use custom tags to describe the structure and other functions of a document.

What is XML

XML Is a markup language created by the World Wide Web Consortium (W3C) to define the syntax for encoding documents that can be read by humans and machines. It does this using tags that define the structure of the document, as well as how the document should be stored and transported.

It is easiest to compare it to another markup language that you may be familiar with - language hypertext markup(HTML) used to encode web pages. HTML uses a predefined set of markup characters (short codes) that describe the format of the content on a web page.

However, XML is different in that it is extensible. XML does not have a predefined markup language like HTML. Instead, XML allows users to create their own markup characters to describe content, forming an unlimited and self-defined character set.

Basically, HTML is a language that focuses on the presentation of content, while XML is a dedicated data description language used to store data.

XML is often used as the basis for other document formats, of which there are hundreds. Here are a few you might want to know:

• RSS and ATOM describe how applications should handle web feeds.
• Microsoft .NET uses XML for its configuration files.
• Microsoft Office uses XML as the basis for document structure.

Thus, if you have an XML file, it does not necessarily tell you what application it is for. However, you do not need to worry about this, unless you are developing XML files.

How to open an XML file

There are several ways to open an XML file directly. You can open and edit them with any text editor, view them with any web browser, or use a website that allows you to view, edit, and even convert them to other formats.

Use a text editor when working with XML regularly

Since XML files are just text files, they can be opened with any text editor. However, many text editors, such as Notepad, are simply not designed to display XML files with their correct structure. This can be useful to quickly familiarize yourself with the content of an XML file. But, there are more convenient tools for working with them.

Using a web browser to view the XML file

If you don't need to edit the XML file, but just need to view the content, your browser can handle this task. What's more, your web browser is most likely already configured as a standard XML viewer. Thus, double-clicking the XML file should open it in the browser.

If not, you can right-click the file to find options to open it with any other application. Just select your web browser from the list of programs.

When the file opens, you should see well-structured data. It's not as pretty as the color look you get in Notepad ++, but much better than Notepad.

Using an online editor for XML files

If you want to edit a random XML file and don't want to load a new text editor, or you need convert XML file to another format There are several decent online XML editors available for free.

TutorialsPoint.com, XMLGrid.net, and CodeBeautify.org - Allows you to view and edit XML files. After editing is complete, you can download the modified XML file, or even convert it to a different format.

Let's use CodeBeautify.org as an example. The page is divided into three sections. On the left is the XML file you are working with. In the middle, you will find several functions. On the right, you will see the results of some of the options that you can choose from.

For example, in the image below, our complete XML file is on the left, and the results pane displays a tree view because we clicked the Tree View button in the middle.

Use the Browse button to load an XML file from your computer or the Load URL button to retrieve XML from an internet source

The Tree View button displays data in a well-formatted tree structure in the results pane, with all tags highlighted in orange and attributes to the right of the tags.

Beatify displays your data in a neat, easy-to-read way.

The Minify button displays your data using the least amount of spaces. This function will place each every piece of data on one line. This comes in handy when trying to make the file smaller, which will save some space.

Finally, you can use the XML to JSON button to convert XML to JSON, and the Export to CSV button to save the data as a comma separated value file, or the Download button to download any changes you made to a new XML file. ...

The Extensible Markup Language (XML) was developed by the World Wide Web Consortium (W3C) XML Working Group. Here's how the creators describe it:

“The Extensible Markup Language (XML) is an integral part of the SGML language ... It is designed to facilitate the use of SGML on the Web and to accomplish the tasks currently performed using HTML. XML is designed to improve the use and interoperability of SGML and HTML. "

This is an excerpt from the XML 1.0 specification, created by the XML Working Group in February 1998. The entire document can be found on the W3C site at http://www.w3.org/TR/REC/-xml.

XML is a markup language designed specifically for posting information on the World Wide Web, similar to the Hypertext Markup Language (HTML), which originally became the standard language for creating Web pages. Since HTML fully satisfies all of our needs, the question arises: Why did you need a completely new language for the Web? What are its advantages and advantages? How does it interact with HTML? Will it replace HTML, or just improve it? Finally, what is SGML, of which XML is a part, and why can't you use SGML proper for your Web pages? In this chapter, I will try to answer all of these questions.

XML purpose

HTML provides a fixed set of elements that you can use to place components on a typical Web page. Examples of such elements are headings, paragraphs, lists, tables, images, and links. For example, HTML is great for

creating a personal home page. Below is the description of the home page in HTML codes:

Michael Young "s Home Page

Welcome to my Web site!

Web Site Contents

Please choose one of the following topics:

• Writing
• Family
• Photo Gallery

Other Interesting Web Sites

Click one of the following to explore another Web site:

• "one. XML should become a language for direct use on the Internet. "

  As you can imagine, XML was designed primarily for storing and distributing information on the Web.

  "2. XML will support a wide variety of applications. "

  Although its main purpose is to distribute information on the Web through servers and browsers, XML is also designed to be used by other programs. For example, XML is used to exchange information between financial programs, to distribute and update software products, and to write voice scripts when delivering information over the phone.

  "3.XML will be SGML compliant."

  XML is a specialized branch of SGML. The advantage here is that SGML software can be easily adapted to work with HTML.

  "4. It will be easier to write programs that process XML documents. "

  Practical use of XML requires that it be easy to write browsers and other programs that process XML documents. In fact, the main reason for separating XML from SGML was the availability of writing programs to process XML documents.

  "5. The number of additional features in XML should be kept to a minimum, ideally zero. "

  The minimum number of additional functions in XML makes it easy to write programs to process XML documents. The abundance of additional pluggable features in SGML has become a major reason why it is practically unsuitable for presenting Web documents. Additional SGML features require tag delimiter characters to be overridden (usually ) and skip the end tag to allow the processor to detect the end of the element. When strictly writing an SGML document processing program, you must consider the possibility of all additional functions, even if they are rare.

  "6. XML documents should be understandable and clear to the user. "

  XML aims to become the lingua franca (universal language) for the exchange of information among users and programs around the world. According to this concept, users, as well as specialized programs, should be able to create and read XML documents. Accessibility and transparency for the user sets XML apart from most other formats used in building databases and text documents.

  The XML document can be easily read by the user because it is described in plain text and has a logical hierarchical structure in the form of a tree. You can simplify XML documents by assigning meaningful names to elements, attributes, and objects, and adding helpful comments. (This is discussed later in this chapter.)

  "7. XML development should be completed quickly enough. "

  XML will become an accepted standard only if programmers and users accept it. This standard should be created before society accepts alternative standards that are increasingly being created by software companies.

  "eight. XML should be formal and concise. "

  The XML specification is written in a formal language used to represent computer languages, with a notation known as the Extended Backus-Naur Form (EBNF). This formal language, although difficult to understand, is devoid of ambiguity and greatly facilitates the writing of XML documents, and especially the programs for processing them.

  "9. XML documents will be easier to create. "

  Practical use of XML as a markup language for Web documents simplifies not only the writing of processing programs, but also the process of creating the XML documents themselves.

  "10. The compressed form is not important in XML markup. "

  In accordance with clause 6 (the XML document must be clear and understandable for the user), the XML markup should not be overly compressed so as not to conflict with the stated purpose.

  Standard XML Applications

  You can use XML for more than just describing an individual document. An individual user, company, or standards committee can define the required set of XML elements and document structure to apply to a particular class of documents. Such a set of elements and a description of the structure of a document is called an XML application or XML vocabulary.

  For example, an organization can define an XML application for creating documents that describe molecular structures, human resources, multimedia presentations, or contain vector graphics. At the end of the chapter, there is a list of some common XML applications that have already been created and are planned to be created.

  An XML application is typically defined by creating a Document Type Descriptor (DTD), which is a valid XML document component. A DTD is structured around a database schema: it sets and defines the names of elements that can be used in a document, the order in which elements can appear, the attributes of elements that can be applied, and other features of the document. For practical use of an XML application, you usually include its DTD in your XML document; the presence of a DTD in a document limits the elements and structures that you will use, so your document meets the standards of this application. The XML document descriptions discussed earlier in this chapter did not include DTDs. You will learn how to define and use DTDs in Chapter 5.

  The advantages of using standard XML applications to design your documents are that you can share documents with all other users of the application, and the document can be processed and displayed using the software that is already built for the application.

  XML applications that enhance the quality of XML documents

  In addition to XML applications for describing specific classes of documents, there are several XML applications that you can use within any type of XML document. These applications make it easier to create a document and improve its quality. Below are examples of such applications.

  • Extensible Stylesheet Language (XSL) allows you to create powerful style sheets using XML syntax.
  • XML Schema allows you to design detailed schemas for your XML documents using standard XML syntax, which is a more powerful alternative to using DTDs.
  • XML Linking Language (XLink) gives you the ability to link your XML documents. It supports multiple targeted links and other useful features, providing more freedom than HTML link organizing mechanism.
  • XML Pointer Language (XPointer) allows you to define flexible target links. When you use XPointer and XLink together, you can organize links to anywhere in the target document — not just jump to highlighted items.

  XLS is covered in Chapter 10. Other XML applications are not yet ready to go and are not covered in this book. (XLink and XPointer are not supported in Internet Explorer 5).

  As you can see, XML is not only a useful tool for describing documents, but also serves as a basis for building applications and extensions that may be needed as the Internet develops.

  Real use of XML

  While the concept of XML is quite interesting, you might wonder how to put it into practice. This section provides a list of examples of such uses of XML, both widely used and promising. If there are relevant XML applications for practical use, they will be shown in parentheses. For example, you might find out that the MathML XML application will allow you to format mathematical formulas.

  Link... For a more complete list of current and emerging XML applications, including their detailed descriptions, see the Oasis SGML / XML Web page (http: //www.oasis-open.arg/cover/ocml.htmW applications).

  • Working with databases. Like traditional databases, XML can be used to assign a label to each field of information within each database record. (For example, you can tag each name, address, and phone number inside address list entries.) You can then display the data in a variety of ways and organize searches, sorting, filtering, and other processing of the data.
  • Structuring documents. The hierarchical structure of XML documents is ideal for marking up the structure of documents such as novels, scientific papers, and plays. For example, you can use XML to mark up a play with acts, scenes, characters, storylines, scenery, and so on. XML markup enables programs to display or print a document in the required format; find, extract or manipulate information in a document; generate tables of contents, summaries and annotations; process information in other ways.
  • Working with vector graphics (VML - Vector Markup Language).
  • Multimedia presentations (SMIL - Synchronized Multimedia Integration Language, HTML + TIME - HTML Timed Interactive Multimedia Extensions).
  • Description of channels. Channels are Web pages that are automatically sent to subscribers. (CDF - Channel Definition Format).
  • Description of software packages and their relationships. Such descriptions provide distribution and updating of software products on the network (OSD - Open Software Description).
  • Interaction of applications over the Web using XML co-communications. These messages are independent of operating systems, object models, and computer languages ​​(SOAP - Simple Object Access Protocol).
  • Sending electronic business cards via e-mail.
  • Financial information exchange. The exchange of information in an open and understandable format is carried out between financial programs (such as Quicken and Microsoft Money) and financial institutions (banks, public funds) (OFX - Open Financial Exchange).
  • Creation, management and use of complex digital forms for commercial Internet transactions. Such forms may include digitized signatures that make them legally recognized (XFDL - Extensible Forms Description Language).
  • Exchange of requests for employment and resumes (HRMML - Human Resource Management Markup Language).
  • Formatting mathematical formulas and scientific information in
  • Web (MathML - Mathematical Markup Language).
  • Description of molecular structures (CML - Chemical Markup Language).
  • Coding and display of information about DNA, RNA and strands (BSML - Bioinformatic Sequence Markup Language).
  • Genealogical Data Markup Language (GeDML).
  • Astronomical Markup Language (AML) exchange.
  • Creation of musical scores (MusicML -Music Markup Language).
  • Working with voice scripts to deliver information over the phone. Voice scripts can be used, for example, to generate voice messages, product availability inquiries, and weather forecasts (VoxML).
  • Processing and delivery of information by courier services. Federal Express, for example, already uses XML for this purpose.
  • Presentation of advertising in the press in digital format (AdMarkup).
  • Legal filing and electronic exchange of legal information (XCL - XML ​​Court Interface).
  • Weather Observation Markup Format (OMF) coding.
  • Exchange of information on transactions with real estate (RETS - Real Estate Transaction Standard).
  • Exchange of insurance information.
  • Exchange of news and information using open Web-standards (XMLNews).
  • Presentation of religious information and markup of texts of worship (ThML - Theological Markup Language, LitML - Liturgical Markup Language).