XML in 10 theses

XML, XLink, Namespace, DTD, Schema, CSS, XHTML... If you for the first time have collided{faced} with XML, it is difficult even to understand, with what to start. This short review represents attempt to capture basic ideas XML that the newbie could see the concept as a whole, not being confused in details. If you represent someone XML why to not begin with these 10 theses?

1. XML is a way of recording of the structured data

" The structured data " usually mean objects such as spreadsheets, directories, configuration parameters, financial tranzakcionnykh recordings, technical drawings and to that similar. XML represents a set corrected (you can count also their instructions or agreements) for development of text formats which will allow you to structure your data. XML is not the programming language, and you do not need to be the programmer to use or study it . XML facilitates to a computer a problem  of creation and data reading, providing thus unambiguity of their structure. XML allows to avoid the widespread mistakes of designing of languages: he is expanded, independent of a platform, includes support of internationalization and localization. XML it is completely compatible with Unicode.

2. XML it is a little similar on HTML

As well as in HTML, in XML tags (the words made in ' <'and'> ') and attributes (a kind a name = "value") are used. But if in HTML semantic value of each tag and attribute and often how the text between them will look in a browser is fixed, in XML tags are used only for a logic marking of the data, and their interpretation is left at the discretion of the processing program. In other words, if you meet "<p>" in a XML-file it is not necessary to think, what is it the paragraph. Depending on a context, it can be the price (price), parameter (parameter), the person (person...) (in general who has said, what is it there should be a word beginning with "p"?)

3. XML is a text, but he is not intended for reading

Programs which work with spreadsheets, directories or other structured data, often save these data on a disk, using either binary, or a text format. One of advantages of a text format is that people if necessary can look through the programs given without use in which they have been created. At the worst, you can read the data which have been written down in a text format, in the liked text editor. Also text formats facilitate to developers debugging of the applications. For these reasons, similarly to HTML-files, XML-files are text: they are not intended for reading by people, but can be if necessary read. However rules for XML-files are much strict, than for HTML. The missed tag or attribute without inverted commas will make a file unsuitable whereas in HTML it is obviously allowed or, at least, it is supposed. As it is written in official specification XML, applications are not allowed to try to foresee the founder of an incorrect XML-file; if the file is incorrect, the application there and then should stop and give out the message on a mistake.

4. XML it is deliberately verbose

As XML - the text format also uses tags for a marking of the data, XML-files almost always it is more on the size, than similar in a binary format. It was the conscious decision of developers XML. Advantages of a text format are obvious (see item{point} 3), and lacks can be usually compensated at other level. The disk space is not so expensive, as was earlier, and programs such as zip and gzip can compress text files very well and very quickly. Besides communication reports, such as modem reports and HTTP/1.1 (the basic report of the Network) can compress the data "hurriedly", saving, thus, bandwidth as is effective, as well as in a case with a binary format.

5. XML is a family of technologies

In specification XML 1.0 it is defined{determined}, that such "tags" and "attributes". But for XML 1.0 "family XML" - more and more growing set of the modules giving useful services for the decision important and often of the arising problems{tasks} follows. For example, in specification XLink the standard way of addition of hyperlinks in XML-document. XPointer is described - syntax for addressing parts of XML-document. XPointer is a little similar on URL, but instead of the instruction{indication} to documents in the Network, addresses to fragments of the data inside a XML-file. Cascade tables of styles CSS can be applied to XML-documents the same as and to HTML. XSL - more advanced language of style tables. He, in turn, is based on XSLT the language of transformations used for rearrangement, addition and removal{distance} of tags and attributes. DOM represents the standard interface for a manipulation files XML (and HTML) from various programming languages. Languages XML Schema 1 and 2 are called to help developers precisely to define{determine} their own formats based on XML. Except for listed it is ready to use or there is in development still a set of modules and means. Watch{keep up} for obnovlenijami on page of technical reports W3C.

6. XML it is new, but not absolutely

Development XML began in 1996, and since February, 1998 is standard W3C that can force to think you of this technology as about rather not mature. But, actually, she is not too new. Up to XML was SGML, developed in the beginning 80 and accepted as standard ISO in 1986 which was widely used in the projects connected to a plenty of the documentation. And, certainly, HTML which development began in 1990. Founders XML have simply taken best of SGML, and, being based on experience HTML, have created something new, that on the power does not concede SGML, but it is much accurater and easier for use. Sometimes evolution, however, is difficult for distinguishing from revolution... Also it is necessary to notice, that while SGML basically it is used for the engineering specifications and in much smaller degree for other kinds of the data, with XML all just what isn't needed.

7. XML conducts HTML to XHTML

There is the important XML-application being a format of documents: W3C XHTML, successor HTML. The majority of elements XHTML same, as well as in HTML. Syntax has been a little changed for conformity to rules XML. The document being "XML-based", inherits syntax XML and limits to his  certain way (for example, in XHTML it is authorized "<p>", but not "<r>"); this syntax also is allocated with semantic value (XHTML defines{determines}, that "<p>" designates "paragraph" (paragraph), instead of "price" (price), "person" (person) or something else).

8. XML - modular technology

XML allows you to define{determine} new formats of documents, combining and reusing already created. As two formats developed independently, can have elements or attributes with identical names, at their combination it is necessary to be careful (that should distinguish "<p>", designating "paragraph" in one format, from "person" in the friend?). For elimination of possible{probable} mess at simultaneous use of different formats XML gives the mechanism of spaces of names. XSL and RDF are good examples based on XML the formats using spaces of names. XML Schema it is developed for reflection of similar support modul`nosti at a level of definition of structures of the XML-document, facilitating process of construction of the new circuit on the basis of existing.

9. XML - a basis for RDF and the Semantic Network

W3C Resource Description Framework (RDF) is the text format based on XML which supports the description of resources and the metagiven applications, such as lists of musical compositions, photo galleries and bibliographies. For example, RDF presumes to identify to you people in a network picture album, using the information from the personal list of contacts; then your mailer can automatically begin letters to these people with the statement, that their photos are in the Network. Just as HTML has united documents, the menu and forms, having given rise to a today's Network, RDF unites applications and agents in the Semantic Network. The same way, as people require agreements on sense of words which they use among themselves in dialogue, and computers for effective interaction require the mechanism of the coordination of values of terms. Formal descriptions of terms of some area (for example, a campaign on shops or manufactures) are called ontologijami and are a necessary part of the Semantic Network. RDF, ontologii, and performance of values so that computers could help people in their job - all this subjects of activity Semantic Web Activity.

10. Technology XML is free from licensing, platformo-independent and well supported

Choosing XML as a basis for the project, you have access to the big and more and more growing family of tools (one of which already, can, does{makes} that is necessary for you!) and to experience of the experts working with this technology. Choice XML is a little similar to choice SQL for databases: all of you still should build the database and write the programs and procedures for job with her, however there are many tool means and people, capable to help you. And as XML it is free from licensing, you can build the software, not having paid somebody copecks. The big and more and more growing support defines{determines} that you are not adhered to any concrete manufacturer of programs. XML - not always the best decision, but always it is necessary to take it  into consideration.