xml

The XML is the abbreviation of the Language of the eXtensible Markup.Expanding marking language XML is a kind of simple data saving language, use a series of simple marking description a data, but these markings can use a convenient way establishment, although the XML take up of the space wants to take up more spaces than the binary system data, the XML be very to in brief be easy to control with use.

XML and Access, the Oracle is different from the SQL Server etc. database, the database provided a more powerful data saving with analytical skill, for example:Data index, line up a preface, check to seek, related consistency etc., the XML is only a demonstration data.In fact XML with other data manifestations' biggest dissimilaritieses BE:He is very simple.This be an advantage which has a liking for to have a little trivial details, but is exactly this to make XML different.

The XML in brief makes it be easy to read and write a data in any applied procedure, this only public language which makes the XML become data commutation very quickly, although different of the applied software also supports an other data commutation a format, soon after they all support XML, that means that the procedure can be more easy of and under the Windows, Mac OS, Linux and other platforms the output information combine, then can very easily add to carry a XML data to procedure in and analyze him, and output a result by XML format.

The XML precursor is a SGML(the Language of the Generalized Markup of the The Standard), is the GML which has develop since 60's from the IBM(the Language of the Generalized Markup)

Together the HTML is similar, the XML(can expand marking language) is in general use statures of the standard(SGML) of the marking language to gather, it is describe a network up of data contents and the standard of structure.For all that, XML not elephant HTML, the HTML only provided to show the in general use method(have no context related with dynamic state function) of information on the page, XML then logarithms according to give the context the related function, it inheritted SGML big and parts of functionses, but used a not that complicated technique..

For making the SGML seem to be customer amity, the XML redefined SGML some internal values and parameter and threw away to in great quantities seldom use of function, these complicated functions make the SGML seem to be a complication while design website.The XML reserved SGML structure to turn function, so make website design can define own text file type and the XML also releases a kind of new text file a type in the meantime and make the developer need not define text file a type, either.

Because the XML is the W3 C establishment of, the XML work set of W3 Cs is responsible for standardize of XML work, the cause of the group's member constitutes from the expert of each place and profession, they pass email exchanges the opinion of the standard to the XML, and put forward an own viewpoint(www.w 3.Org/TR/WD-xml).Because the XML is a public format,(it is no more exclusive than any company) , you need not worry that the XML technique will become a handful of earnings tools of companies and the XML isn't a language which depends on at the particular browser

XML(can expand marking language) from be called SGML(standard in general use marking language) more ancient language parties to living out.SGML main purpose is definition usage label to mean a data of marking language of phrasing.

Label from surround small big with one in one at the number(<) between the number(>) of the text originally constitutes, for example.Start label(start tag) means the beginning of a particular district, for example;End the label(end tag) defined a be over of district, in addition to at small at the number after a close behind oblique line(/) outside, basic and similar with start label, for example.The SGML still defined the characteristic(attribute) of label, they were definitions at small at the number and big between the number of value, for examplein of src characteristic.If you feel that it looks to acquaint with very much, should know, according to SGML language of most the Zhao realization be an original HTML.

The SGML is in common use to define the text file type definition(DTD) of aim at the HTML, it is also in common use in the meantime in write XML DTD.The SGML problem lie in, it allows to appear some strange phrasings, and this resolution machine which lets to establish HTML becomes a great hard nut to crack:

1 Some start labels disallow to appear be over label, for example HTML inlabel.Containment's concluding to tie label will appear a mistake.

2 Some start labels can appear be over label by selectivity perhaps implicit conclude to tie label, for example HTML in

label, be appear another

label perhaps some and other labels, then suppose have a be over label before this.

3 Some start labels request and have to appear be over label, for example HTML inlabel.

4 The label can be with any in proper order Qian set.Even don't according to the negative preface of start label end label to appear to also allow, for example, This is a sample stringBE correct.

5 Some characteristics request and have to include a value, for examplemedium src characteristic.

6 Some characteristics don't request and must have a value, for examplemedium nowrap characteristic.

7 The both sides which defines characteristic has to plus a pair of all of quotation marks is can, soandall allow.

These problems made to build up a resolution machine of SGML language to become a mission with huge Jian.Judge when applied above regular of the difficulty caused SGML language of the definition has been bog down.Use these problems as point of departures, the XML follows our visual fields gradually.

Make many SGMLs that the development personnels have a headache at will phrasing before XML threw away.In the XML, the phrasing adopting as follows:

8 Any start label has to have a be over label.

9 Can adopt another simplification phrasing, can mean start and be over label in the meantime in a label.This kind of phrasing is at big at the sign before follow close behind an oblique line(/), for example.The XML resolution machine will translate it into.

10 The label has to press suitable in proper order carry on a Qian set, so the be over label has to press the mirror to be like sequence to match start label, for examplethis is asample string.This compare to is the or so brackets which sees start and be over label as be in mathematics:It is the brackets that can't close an outside before having no close all internal bracketses.

11 All characteristics have to have a value.

12 All characteristics have to a pair of quotation marks in the around plus of the value.

These rules make to develop a XML to analyze a machine to want simple have to be many, and also remove the work that the resolution spends to when and where apply those strange phrasing rules in the judgment in the SGML.Just after the XML appear of the first 6 yearses spread out various different languages and include MathML, SVG, RDF, RSS, SOAP, XSLT, XSL-FO, and also improve the HTML as XHTML in the meantime.

If need contrast concerning the SGML and the XML concrete technique, please look into the W3 Cs comment and Be located on:http://www.w3. org/TR/NOTE-sgml-xml.html

Now, the XML is already in the world to develop one of the quickest techniques.It of main purpose is use a text originally is turn with structure of way to mean a data.At some aspects, the XML document is also similar at the database and the structure which provides a data turns to see diagram.BE an example of XML document here:


Each XML text file from XML preface beginning, in the code of front of the first would be XML preface, .This code will tell resolution machine and browser, this document should according to before talked over of the XML rule carry on resolution.The second code, , then text file chemical element(document element), it is an outmost label in the document.(we think that the chemical element(element) is the contents of of start label and be over label)All other labels have to include in this label inside to constitute a valid XML document.XML document of the second combine to need to include text file a chemical element not necessarily;If have the annotation perhaps other contentses, text file chemical element can a little more late emergence.

The third code in the example document is an annotation and you will discover that it is similar with the annotation style of usage in the HTML.This be one of the phrasing chemical elements that the XML inherits from the SGML.

Page again downwards some places, can discoverthere are some special phrasings in the label.the code used for the text which means to have never need to carry on resolution originally, allow such as big include in the text the origin at the special character list of the number and the type smaller than number, but didn't need phrasing of worry the breakage XML.The text originally has to appear atof then can suitablely avoid being analyze.So of the text is originally called Character Data Section, brief name CData Section.

1 line of underneath be at the second definition of book previous of:



Although it has a liking for to be like XML preface very much, actually is a kind of phrasing of different type which is called processing instruction(processing instruction).The purpose which handles instruction(call PI as follows) is for give processing page of the procedure(for example the XML analyze a machine) provide an additional information.PI usually under the circumstance is have no fix format, the only request's is to close on the heels of the first question mark has to have a letter of alphabet at least.After this, the PI can include in addition to small at the number with more than any string sequence out of the number.

The most familiar PI is the style form which uses to an appointed XML document:



This PI generally will directly put after the XML preface, usually from Web browser usage, come out the XML data is with the special style manifestation.