XML ïðåâîñõîäèò ñàìîå ñåáÿ

Application XML for the decision of practical problems assumes improvement of the description of documents and an output in the world of an exchange of messages.

Let's assume, that you have convinced of value of expanded language of a marking (Extensible Markup Language, XML). What further? To buy editor XML and to wait, while all becomes on the places? Whether everyone who will encounter your documents, will understand your language, in fact XML is a self-documented format of a marking?

Undoubtedly, documents which differently would be created on HTML, it is possible to store all as XML together with nicoaaeaiiuie you explanatory tegami. At the given stage of development Web you should use a server for transformation XML in HTML if you want that any interested person could look through documents XML as pages Web, but this insignificant inconvenience will be kept only until browsers in the world not begin to understand all XML. Possibly, till this moment you can take advantages from following to a correct practice of coding, in particular the toolkit of search can distinguish different tegi, for example that Network has other sense, rather than Network.

However search by search, but business gets rather curious a turn when you should exchange similar information filling with other people collecting the information in close subject domains. Document XML can be adhered to the table of styles and then addressees will see it in accuracy such what you conceived.

However if you agree about business operations according to the terms expressed by means of the corresponding marking can suddenly find out that is a question of the much greater rate, than simply appearance. Even in case of the most obvious examples like " the book, the name, the author " with which textbooks on XML abound, you inevitably will collide with troubles if will consider, that everyone mark the information in the same way, as you.

Thus, one of tendencies in world XML consists that with a view of simplification of information interchange between branches the description of the document aspire to make as more as possible expressive, on the one hand, and as more as possible predicted - with another. In this clause we shall consider, how it can be made, on an example of initiative BizTalk Framework of company Microsoft and system XML Schema accepted by her for the description of the documents.

Besides XML leaves for limits originally allocated to it; it any more is not limited to exclusively independent documents with information filling. Now numerous works are conducted above use XML for definition of sequences of the messages made on XML. Their results can be found and in BizTalk, but, probably, most mature example is the report of an exchange of information filling Internet (Internet Content Exchange, ICE). ICE serves as an excellent example of how the branch can solve the problems by means of an exchange of messages on the basis of XML.
CONVERSATIONS ABOUT BIZTALK

XML it is sometimes described as system for self-documenting data. We shall not think out anything new and we shall consider a standard example with the elements making the information on the book: John Milton Poterjannyj paradise

If you will show this formulation during presentation present according to zakivajut, agreeing, that a name of the author really it is meaningful to allocate the majority in a separate element of data and to give it semantic teg.

But the real life is much more complex, even if you are limited to predicted enough concept of the book. Traditionally author " Sawyer's Volume " Mark Twain is considered, but the real person received fees under name Samuel Klemens. Whether you Should create another teg for pseudonyms? Or to use teg with attribute nametype=pseudonym? How to distinguish different editions? Whether data about copyrights will be described by means of attributes tega or their each element will have separate teg inside of an element? If two book shops realize own appendices and then will decide to exchange data from the catalogues who will check correctness of conformity?

Except for pair the cases which are not having the attitudes to business, Consortium World Wide Web (W3C, http: // www.w3.org) has precisely designated the position: it is not going to give the blessing to any appendices XML (in terminology XML "appendix" the description of branch terms by means of some set tegov XML refers to, it has no attitude to software packages). In other words, the concrete vertical markets should coordinate independently inside of branch names for the objects. To promote an openness and predictability at drawing up of schemes XML in vertical branches, Microsoft has put forward the initiative named BizTalk. As of August, 1999 this initiative has supported over 25 companies.
COLLECTIVE WISDOM

Partly BizTalk represents not that other, as public server Web (http: // www.biztalk.org) where the schemes offered for use in various branches are published all. Markus Schmidt, the manager on work with the companies specializing in the field of deliveries, speaks, that Microsoft and other members of Initiative group BizTalk work above recommendations and tegami XML for giving some monotony to use XML in business. However BizTalk does not set as the purpose to unite all branches in attempt to make one huge scheme for all data used in any business. " We very well understand, that never we can force to come various branches to the consent even in occasion of fundamental things, for example concerning definition of the customer as the information on the customer is required to each of them. We try to achieve that when the manufacturer will decide to make the own scheme, it had higher chances that its scheme will be compatible with someone's else if it begins to follow our recommendations and if others will have an opportunity without effort to receive its scheme that they could establish conformity between the and its scheme ".

As a whole as Schmidt explains, BizTalk consists of three separate elements. First, this storehouse on server Web together with recommendations and tegami XML, used for addition of new schemes in storehouse. Secondly, it is development of software product, server BizTalk. And thirdly, it will be interactive services on the basis of technology BizTalk.
REFUSAL FROM DTD

In that, as to display of branch data, BizTalk starts with hopelessness of definitions of types of documents (Document Type Definition, DTD). Instead of encouraging development XML DTD, supporters BizTalk describe the hierarchies of data by means of XML Schema (as it is supposed, this standard should come in the stead DTD). " DTD some internal restrictions are peculiar, - Schmidt explains. - therefore many people and groups offer the decisions ".

Now W3C tries to coordinate various approaches to schemes, but the offered version of the standard - XML Schema - gives clear enough representation how replacement DTD. XML Schema will look has considerably more ample opportunities, rather than DTD, and descriptions are given by means of direct XML, without creation of one more system of a marking as that demands DTD (see vrezku " the New scheme ").

At general level BizTalk Framework demands, that publishers XML Schema adhered to the certain recommendations which most part is based on the standard practice of development of the software. So, tegam it is offered to give the intelligent names with the clear not reduced writing; these names should correspond to functional purpose of the information, instead of its place in private structure of data (for example, "PartLocation" instead of "PartFieldFourteen"), and containing in tege the information should not demand special, distinct from XML, decoding (for example, the designation of currency of a sum of money should be stored in the form of element XML instead of join the sum as in "$30US"). These recommendations are called to facilitate a life that who will try to decode the concrete scheme.

Necessary components BizTalk Framework are special, the general for all branches tegi XML. These tegi are called to release developers from cares in occasion of three major problems of interaction of appendices. First, how data are transferred from one appendix in another; secondly, how "to cause" other appendix - sendings to the appendix of data in format XML should be enough; thirdly, from in what order elements of data should follow.

So these do tegi? One of them defines a code by means of which accepting data in format XML the program can establish, that for scheme BizTalk is used. By means of others tegov the appendix can find out, who is the sender of data, that the sender wants from it also to whom data should be then transferred. " In the same way on the basis of the information on an envelope mail defines, how it is necessary to act with the letter, thus it does not have any business, as it contains in what kind ", - Schmidt explains.

For maintenance of compatibility document BizTalk should begin and, accordingly, to come to an end tegom BizTalk that the addressee knew, that it has entered sector BizTalk. Teg MsgType sets space of names XML (your concrete scheme), defining admissible elements of the document. As your scheme uses a format of data XML (as is described in vrezke " the New scheme ") type of data with which you fill the document, it will be easy to establish. At last, you can insert the block of routing documents also.

BizTalk Framework nothing speaks about what data should enter into four attributes tegov and, it simply establishes purpose of each of them. Tegi location identify network unit (probably, by means of URL) where the document while tegi process goes and handle define the appendix and a concrete copy (for example, number of transaction) to which data concern.

Teg path serves some kind of a receptacle, where intermediate servers can store data on date and other information, that the route (and by means of expansion a return route) was visible to all servers along a way.

The general format of full message BizTalk is shown in vrezke " Anatomy of message BizTalk ".
BUSINESS-MODEL BIZTALK

Considering, what these specifications of documents are popular and any interested person can use schemes BizTalk free of charge, you can reasonably ask, how Microsoft is going to profit by means of XML? The Answer is simple - due to sale of toolkit XML.

As Schmidt considers, the main source of profit for Microsoft should become a server product for regulation of an exchange by BizTalk-compatible messages XML between partners on business. As he said, the aaoa-version of this product should appear in the end of autumn of 1999; the ready product should leave after Windows 2000.

Probably also, that to one of sources of profit can become the operative services focused on the concrete markets (on such units, as Microsoft MSN) where BizTalk it will be used by manufacturers for the message to market service about the offer of new products and special discounts.

As Schmidt if such operative service will appear it will not be based on server BizTalk as it is intended only for the purposes of creation of library and the public center where the companies and developers could exchange ideas freely explains. " We do not consider biztalk.org as a portal for the organization of transactions between the companies ", - Schmidt assures. During present time the basic efforts BizTalk are concentrated to that branch groups have accepted BizTalk Framework as the general denominator of their efforts in the field of XML.
XML ATOP ICE

Irrespective of the fact how document XML - by means of DTD or XML Schema is structured, - its splitting into separate elements (problem DTD and schemes) is only a part of the general picture. Not less great value - if, certainly, you are going something to reach by means of the document - have rules and the recommendations, the concerning uses of documents XML set within the limits of defining DTD or the scheme.

Necessity for " rules of use " (t. e. Reports) becomes obvious in case of the companies which primary goal consists in creation of documents. Such company is, for example, news agency " ?aeoa? ". For certain, travelling on Web, you have paid attention, that recently "caps" "Rejter" began to flash here and there.

Before occurrence ICE every time when "Rejter" entered into the agreement with any server Web about inclusion of the information filling, to both parties was necessary to resort to additional programming that headings and blocks of news could be integrated into target unit Web.

Considering that the basic expenses for distribution of news, thus, fell to redefinition of connections and transformations, some players in the market were united for creation ICE - the report of the base mechanism of regular newsfeed. In July, 1999 representatives of initiative group of developers of products for ICE, news agencies and their subscribers have gathered in Chicago on ICE Summit. This meeting has been organized by Research institute of Association of graphic communications.
ICEaa?a. The package (or useful loading as the full message refers to) Internet Content Exchange (ICE) contains mainly one or the several tegov elements ICE, and those, in turn, can include text filling in format XML, binary data in the coding base64 or URL, specifying on stored in Web a file which should be loaded and included as a part of useful loading.

The meeting has shown, that ICE has reached critical weight for creation of products working on its base and that at least some companies use the given report for the decision of the problems (see vrezku " Three realizations ICE "). It not that report where all device installed (its claims is redefined much more modestly), but it satisfies quite certain needs of business and does the business in view of all subtleties of a solved problem, avoiding thus of any excesses. Specification ICE contains DTD, defining what should be messages with various inquiries and answers both at negotiations about a new subscription, and by granting information filling. (meanwhile the initiative group avoids use XML Schema as that should be still modified and accepted W3C.) ICE differs from typical appendix XML that in it XML is applied to formatting messages inside of the report, instead of for definition of more traditional documents. Besides while XML serves for granting the marked documents to the client (to usually browser Web which is carried out by the machine of the end user) more often, ICE it is intended mainly for interserver communications, where necessity for visual data presentation (and participation of the person) is absent.

ICE allows news agency to offer the scheme of delivery and corresponding conditions of a subscription in format XML. ICE describes not only elements of data in structure of the offer, but also and methodology of an exchange of copies of offers during the coordination of final conditions. For example, the news agency can offer the subscriber access for loading information filling on days off with 2 up to 3 one o'clock in the morning. However to the subscriber it can appear inconveniently as at this time it loads information filling from other sources, therefore it can make the counteroffer about transferring time of loading on an hour later.

In such a way ICE allows to coordinate the following two aspects of a subscription: first, as the subscription - by inquiry of the subscriber (pull) or on channels of agency (push) will be delivered; secondly, what will be the schedule of delivery.

On ICE Summit Rik Levin, architect Web in b has noted, that servers will coordinate only technical, instead of the financial or information party of the agreement. " Participation of the person at registration of a subscription to news will be still necessary. A business supper to manage it will not be possible ". As it marks, turn ICE comes after the conclusion of the contract. ICE is a system for delivery of information filling, and this system understands adjustments which the provider of news information filling would like to apply to the intellectual property.

In a typical situation the provider of information filling would like to transfer regular updatings of some segments of the information filling to client server Web, and that in turn would like to integrate the received information filling into the structure. It is that type of business agreements, which news editions long since concluded with publishers of comics and programs of telecasts, - and as it is possible to see, comics and programs of transfers to this day collect an extensive subscription in Web.

Not mentioning all details of the order of an exchange of messages and mechanisms of acknowledgement, nevertheless it will be useful to look, as typical delivery is carried out at use ICE. The general scheme is resulted in Figure. Apparently, the message consists of useful loading (group of information components) and an envelope where it is located - only your base heading of document XML and pair corresponding tegov.

Useful loading also is formalized by means of tegov XML. Besides the control over how elements are processed, are described in useful loading by means of properties corresponding tegov XML. Force of the report, in comparison with earlier and trivial format of definition of the channel (Microsoft Channel Definition Format), consists that ICE enters constant elements of a subscription. For example, news always should have heading. The maintenance of heading can vary, but to it the certain place where it always can be found is allocated.

ICE describes some variants of inquiry of data (at distribution by inquiry of the subscriber) or simple sending of data (on channels of agency or in reply to inquiry). Most important of these options is the opportunity of the task of conditions defined by agency in history of delivery of messages and return of information filling to this condition on demand. Having thought, you will understand, that here ICE falls outside the limits powers XML, and definitions ICE start to live own life because in this case ICE specifies, what program (instead of it is information-oaio?e?aneea) opportunities should have realizations ICE.
TEG IS A MESSAGE

ICE is far not the unique offered standard where XML it is applied to definition of the communication report. By the way, already one teg as it is certain in BizTalk, places branch sets of data on the conveyor of messages. So, some more reports Internet are similarly described by means of XML. It, for example, Platform for Privacy Preferences (P3P) and Synchronyzed Multimedia Integration Language (SMIL, it is said as "smajl"). Also it is not necessary to doubt, that soon will appear still.

These children of two initiatives - one, aspiring more strictly and full to regulate, that should represent itself correctly made document XML, and to the second, decided to apply XML to "dialogue" appendices, - show, that XML it will not be possible to bring under one measure.

In basis XML it is very simple, but in the real world different problems, such as transformation of styles, specifications of printed data and hierarchical schemes, mix up so vigorously, that as a result we risk to receive a baroque bouquet of angular brackets. However in view of that tools for ordering chaos XML everyone become better, it is quite probable, that its complication will have a positive effect as it will allow to solve by means of XML and other problems of the computing world. But we should reckon with the fact, that, as well as HTML up to it, XML has independent value and a circle of problems.
Robert Richardson - non-staff editor Network Magazine. It has organized free-of-charge electronic magazine Small Office TECH to the address of: http: // www.smallofficetech.com.
The new scheme

Though practically in any review XML (not excepting and clause " XML: time has come ") is spoken, that the grammar and syntax of correctly made document XML are defined DTD, most likely, days DTD are already found. On change DTD the new standard - XML Schema. Should come

DTD it is quite enough for base definition of the document, but they have some lacks. First, they are given not on XML. Considering a high degree of an adaptability and expansibility XML, presence of one more format for definition of documents is represented excessive.

Secondly, elements DTD inside of document XML demand full definition of everything that is inside of these elements. In other words, no subelements " on prospect " are supposed - if those will be present at the document, that, by definition, the document will not be correctly made. Meanwhile definitions XML Schema use model of the open information filling in which uncertain elements are quite admissible.

Thirdly, DTD are limited only to grammar and syntax (t. e. The attitude of one element to another) whereas XML Schema can set also direct restrictions on type of data which the element can contain. It considerably simplifies realization of data transmission of the appendix in comparison with more traditional text document. For example, in the same way, as it is done by developers in programming languages, you can specify in the obvious image, that the given area of storage can contain only integer data. At last, to the developers working in Wintel environments, that circumstance will be rather convenient, that XML Schema is easily displayed on Microsoft Document Object Model. Thus, the program working with documents XML can request of the corresponding scheme an available definition for an element of the document at the choice. The code looks as follows:

var bookNode = doc.documentElement

However as the document containing the scheme from within will look? First, it will contain tegi XML, declaring, that it is the scheme, like:

Each item inside of the scheme appears then individually, and features of each element are deciphered by means of enclosed tegov, for example:

Defines an element as able to contain only text data.

Similar schemes can appear are rather difficult for reading, but they easily give in to analysis by means of tools XML. In other words, the special editor for work with document XML Schema, as in case of DTD. Is not required to you

I shall note also, that in case of rules on the basis of XML for formats of commercial data you can use for display of one scheme to another the built in functionalities of transformation XML - expanded language of tables of styles (Extensible Stylesheet Language, XSL).
Three realizations ICE

On ICE Summit in Chicago in July, 1999 it has been shown three ICE-compatible managers of distribution of news.

WebExpress
Arcadia Technology
http: // www.arcadiatech.com
Whereas while webExpress is available only in the aaoa-version, to speak about what this package differs from the competitors, it would be a little bit premature. However by that has been shown on ICE Summit, it will be direct realization of report ICE without any excesses.

ShiftKey Syndication System
ShiftKey Software
http: // www.shiftkey.com
ShiftKey has decided to raise value of the product due to addition of support of some means of transformation of information filling after its receipt on a server of the subscriber. Eventually, ICE simply delivers information filling in a standard format, and it in fact can and not approach for direct inclusion of data in Web-pages of the subscriber. One of supported ShiftKey methods of transformation - Extensible StyleSheet Language (XSL), it defines, how tegi XML should be displayed in a browser. Necessary transformations describe tables of styles.
As to the server party, ShiftKeySoftware at the moment of the publication of clause was the unique company supporting distribution by inquiry of the subscriber (pull) and on channels of agency (push) and giving server ICE, not adhered to a control system of information filling.

Vignette Syndication Server
Vignette
http: // www.vignette.com
Syndication Server it is considered as a separate product, but its basic purpose consists in simplification of achievement of agreements on newsfeed by means of an available product, instead of in orientation to the market of newsfeed in itself.
Offer Vignette is closely adhered to Vignette Story Server, a control system of information filling Web of the senior class, used by such publishing giants, as Time Warner, Ziff-Davis and Chicago Tribune.
Anatomy of message BizTalk

The accepting appendix learns that this message BizTalk, on the basis of an envelope (it informs the concrete scheme used for a formulation of the given document). It understands a format of your specific data because teg specifies the scheme which you use inside for formatting the data:




Tegi a route





Your document

Resources Internet

The information about BizTalk, including the full specification tegov BizTalk, is available on http: // www.biztalk.org.

Full specification Internet Content Exchange (ICE) is accessible in the interactive image on http: // www.w3.org/TR/NOTE-ice.

The additional information about XML Schema can be found on http: // www.w3.org/TR/xmlschema-1/and http: // www.w3.org/TR/xmlschema-2/.