HOME
The Info List - XML


--- Advertisement ---



In computing, Extensible Markup Language
Language
(XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The W3C's XML
XML
1.0 Specification[2] and several other related specifications[3]—all of them free open standards—define XML.[4] The design goals of XML
XML
emphasize simplicity, generality, and usability across the Internet.[5] It is a textual data format with strong support via Unicode
Unicode
for different human languages. Although the design of XML
XML
focuses on documents, the language is widely used for the representation of arbitrary data structures[6] such as those used in web services. Several schema systems exist to aid in the definition of XML-based languages, while programmers have developed many application programming interfaces (APIs) to aid the processing of XML
XML
data.

Contents

1 Applications of XML 2 Key terminology 3 Characters and escaping

3.1 Valid characters 3.2 Encoding detection 3.3 Escaping 3.4 Comments 3.5 International use

4 Well-formedness and error-handling 5 Schemas and validation

5.1 Document Type Definition 5.2 XML
XML
Schema 5.3 RELAX NG 5.4 Schematron 5.5 DSDL and other schema languages

6 Related specifications 7 Programming interfaces

7.1 Simple API for XML 7.2 Pull parsing 7.3 Document Object Model 7.4 Data binding 7.5 XML
XML
as data type

8 History

8.1 Sources 8.2 Versions

9 Criticism 10 See also 11 Notes 12 References 13 Further reading 14 External links

Applications of XML[edit] The essence of why extensible markup languages are necessary is explained at Markup language
Markup language
(for example, see Markup language
Markup language
§ XML) and at Standard Generalized Markup Language. Hundreds of document formats using XML
XML
syntax have been developed,[7] including RSS, Atom, SOAP, SVG, and XHTML. XML-based formats have become the default for many office-productivity tools, including Microsoft Office
Microsoft Office
(Office Open XML), OpenOffice.org
OpenOffice.org
and LibreOffice (OpenDocument), and Apple's iWork[citation needed]. XML
XML
has also provided the base language for communication protocols such as XMPP. Applications for the Microsoft
Microsoft
.NET Framework
.NET Framework
use XML
XML
files for configuration. Apple has an implementation of a registry based on XML.[8] Most industry data standards, e.g. HL7, OTA, NDC, FpML, MISMO etc. are based on XML
XML
and the rich features of the XML schema specification. Many of these standards are quite complex and it is not uncommon for a specification to comprise several thousand pages. In publishing, DITA is an XML
XML
industry data standard. XML
XML
is used extensively to underpin various publishing formats. XML
XML
is widely used in a Services Oriented Architecture (SOA). Disparate systems communicate with each other by exchanging XML messages. The message exchange format is standardised as an XML
XML
schema (XSD). This is also referred to as the canonical schema. XML
XML
has come into common use for the interchange of data over the Internet. IETF RFC:3023, now superseded by RFC:7303, gave rules for the construction of Internet
Internet
Media Types for use when sending XML. It also defines the media types application/xml and text/xml, which say only that the data is in XML, and nothing about its semantics. The use of text/xml has been criticized[i] as a potential source of encoding problems and it has been suggested that it should be deprecated.[9] RFC 7303 also recommends that XML-based languages be given media types ending in +xml; for example image/svg+xml for SVG. Further guidelines for the use of XML
XML
in a networked context appear in RFC 3470, also known as IETF BCP 70, a document covering many aspects of designing and deploying an XML-based language. Key terminology[edit] The material in this section is based on the XML
XML
Specification. This is not an exhaustive list of all the constructs that appear in XML; it provides an introduction to the key constructs most often encountered in day-to-day use.

Character An XML
XML
document is a string of characters. Almost every legal Unicode character may appear in an XML
XML
document.

Processor and application The processor analyzes the markup and passes structured information to an application. The specification places requirements on what an XML processor must do and not do, but the application is outside its scope. The processor (as the specification calls it) is often referred to colloquially as an XML
XML
parser.

Markup and content The characters making up an XML
XML
document are divided into markup and content, which may be distinguished by the application of simple syntactic rules. Generally, strings that constitute markup either begin with the character < and end with a >, or they begin with the character & and end with a ;. Strings of characters that are not markup are content. However, in a CDATA section, the delimiters <![CDATA[ and ]]> are classified as markup, while the text between them is classified as content. In addition, whitespace before and after the outermost element is classified as markup.

Tag A tag is a markup construct that begins with < and ends with >. Tags come in three flavors:

start-tag, such as <section>; end-tag, such as </section>; empty-element tag, such as <line-break />.

Element An element is a logical document component that either begins with a start-tag and ends with a matching end-tag or consists only of an empty-element tag. The characters between the start-tag and end-tag, if any, are the element's content, and may contain markup, including other elements, which are called child elements. An example is <greeting>Hello, world!</greeting>. Another is <line-break />.

Attribute An attribute is a markup construct consisting of a name–value pair that exists within a start-tag or empty-element tag. An example is <img src="madonna.jpg" alt="Madonna" />, where the names of the attributes are "src" and "alt", and their values are "madonna.jpg" and "Madonna" respectively. Another example is <step number="3">Connect A to B.</step>, where the name of the attribute is "number" and its value is "3". An XML
XML
attribute can only have a single value and each attribute can appear at most once on each element. In the common situation where a list of multiple values is desired, this must be done by encoding the list into a well-formed XML attribute[ii] with some format beyond what XML
XML
defines itself. Usually this is either a comma or semi-colon delimited list or, if the individual values are known not to contain spaces,[iii] a space-delimited list can be used. <div class="inner greeting-box">Welcome!</div>, where the attribute "class" has both the value "inner greeting-box" and also indicates the two CSS class names "inner" and "greeting-box".

XML
XML
declaration XML
XML
documents may begin with an XML
XML
declaration that describes some information about themselves. An example is <?xml version="1.0" encoding="UTF-8"?>.

Characters and escaping[edit] XML
XML
documents consist entirely of characters from the Unicode repertoire. Except for a small number of specifically excluded control characters, any character defined by Unicode
Unicode
may appear within the content of an XML
XML
document. XML
XML
includes facilities for identifying the encoding of the Unicode characters that make up the document, and for expressing characters that, for one reason or another, cannot be used directly. Valid characters[edit] Main article: Valid characters in XML Unicode
Unicode
code points in the following ranges are valid in XML
XML
1.0 documents:[10]

U+0009 (Horizontal Tab), U+000A (Line Feed), U+000D (Carriage Return): these are the only C0 controls accepted in XML
XML
1.0; U+0020–U+D7FF, U+E000–U+FFFD: this excludes some (not all) non-characters in the BMP (all surrogates, U+FFFE and U+FFFF are forbidden); U+10000–U+10FFFF: this includes all code points in supplementary planes, including non-characters.

XML
XML
1.1[11] extends the set of allowed characters to include all the above, plus the remaining characters in the range U+0001–U+001F. At the same time, however, it restricts the use of C0 and C1 control characters other than U+0009 (Horizontal Tab), U+000A (Line Feed), U+000D (Carriage Return), and U+0085 (Next Line) by requiring them to be written in escaped form (for example U+0001 must be written as &#x01; or its equivalent). In the case of C1 characters, this restriction is a backwards incompatibility; it was introduced to allow common encoding errors to be detected. The code point U+0000 (Null) is the only character that is not permitted in any XML
XML
1.0 or 1.1 document. Encoding detection[edit] The Unicode
Unicode
character set can be encoded into bytes for storage or transmission in a variety of different ways, called "encodings". Unicode
Unicode
itself defines encodings that cover the entire repertoire; well-known ones include UTF-8
UTF-8
and UTF-16.[12] There are many other text encodings that predate Unicode, such as ASCII
ASCII
and ISO/IEC 8859; their character repertoires in almost every case are subsets of the Unicode
Unicode
character set. XML
XML
allows the use of any of the Unicode-defined encodings, and any other encodings whose characters also appear in Unicode. XML
XML
also provides a mechanism whereby an XML
XML
processor can reliably, without any prior knowledge, determine which encoding is being used.[13] Encodings other than UTF-8
UTF-8
and UTF-16
UTF-16
are not necessarily recognized by every XML
XML
parser. Escaping[edit] XML
XML
provides escape facilities for including characters that are problematic to include directly. For example:

The characters "<" and "&" are key syntax markers and may never appear in content outside a CDATA section. It is allowed, but not recommended, to use "<" in XML
XML
entity values.[14] Some character encodings support only a subset of Unicode. For example, it is legal to encode an XML
XML
document in ASCII, but ASCII lacks code points for Unicode
Unicode
characters such as "é". It might not be possible to type the character on the author's machine. Some characters have glyphs that cannot be visually distinguished from other characters, such as the non-breaking space (&#xa0;) " " and the space (&#x20;) " ", and the Cyrillic capital letter A (&#x410;) "А" and the Latin capital letter A (&#x41;) "A".

There are five predefined entities:

&lt; represents "<"; &gt; represents ">"; &amp; represents "&"; &apos; represents "'"; &quot; represents '"'.

All permitted Unicode
Unicode
characters may be represented with a numeric character reference. Consider the Chinese character
Chinese character
"中", whose numeric code in Unicode
Unicode
is hexadecimal 4E2D, or decimal 20,013. A user whose keyboard offers no method for entering this character could still insert it in an XML
XML
document encoded either as &#20013; or &#x4e2d;. Similarly, the string "I <3 Jörg" could be encoded for inclusion in an XML
XML
document as I &lt;3 J&#xF6;rg. &#0; is not permitted, however, because the null character is one of the control characters excluded from XML, even when using a numeric character reference.[15] An alternative encoding mechanism such as Base64
Base64
is needed to represent such characters. Comments[edit] Comments may appear anywhere in a document outside other markup. Comments cannot appear before the XML
XML
declaration. Comments begin with <!-- and end with -->. For compatibility with SGML, the string "--" (double-hyphen) is not allowed inside comments;[16] this means comments cannot be nested. The ampersand has no special significance within comments, so entity and character references are not recognized as such, and there is no way to represent characters outside the character set of the document encoding. An example of a valid comment: <!--no need to escape <code> & such in comments--> International use[edit]

This example contains Armenian text. Without proper rendering support, you may see question marks, boxes, or other symbols instead of Armenian letters.

This example contains Cyrillic text. Without proper rendering support, you may see question marks or boxes, misplaced vowels or missing conjuncts instead of Cyrillic letters.

XML
XML
1.0 (Fifth Edition) and XML
XML
1.1 support the direct use of almost any Unicode
Unicode
character in element names, attributes, comments, character data, and processing instructions (other than the ones that have special symbolic meaning in XML
XML
itself, such as the less-than sign, "<"). The following is a well-formed XML
XML
document including Chinese, Armenian and Cyrillic characters:

<?xml version="1.0" encoding="UTF-8"?> <俄语 լեզու="ռուսերեն">данные</俄语>

Well-formedness and error-handling[edit] Main article: Well-formed document The XML
XML
specification defines an XML
XML
document as a well-formed text, meaning that it satisfies a list of syntax rules provided in the specification. Some key points in the fairly lengthy list include:

The document contains only properly encoded legal Unicode
Unicode
characters. None of the special syntax characters such as < and & appear except when performing their markup-delineation roles. The start-tag, end-tag, and empty-element tag that delimit elements are correctly nested, with none missing and none overlapping. Tag names are case-sensitive; the start-tag and end-tag must match exactly. Tag names cannot contain any of the characters !"#$%&'()*+,/;<=>?@[]^` ~, nor a space character, and cannot begin with "-", ".", or a numeric digit. A single root element contains all the other elements.

The definition of an XML
XML
document excludes texts that contain violations of well-formedness rules; they are simply not XML. An XML processor that encounters such a violation is required to report such errors and to cease normal processing. This policy, occasionally referred to as "draconian error handling," stands in notable contrast to the behavior of programs that process HTML, which are designed to produce a reasonable result even in the presence of severe markup errors.[17] XML's policy in this area has been criticized as a violation of Postel's law ("Be conservative in what you send; be liberal in what you accept").[18] The XML
XML
specification defines a valid XML
XML
document as a well-formed XML
XML
document which also conforms to the rules of a Document Type Definition (DTD).[19][20] Schemas and validation[edit] In addition to being well-formed, an XML
XML
document may be valid. This means that it contains a reference to a Document Type Definition (DTD), and that its elements and attributes are declared in that DTD and follow the grammatical rules for them that the DTD specifies. XML
XML
processors are classified as validating or non-validating depending on whether or not they check XML
XML
documents for validity. A processor that discovers a validity error must be able to report it, but may continue normal processing. A DTD is an example of a schema or grammar. Since the initial publication of XML
XML
1.0, there has been substantial work in the area of schema languages for XML. Such schema languages typically constrain the set of elements that may be used in a document, which attributes may be applied to them, the order in which they may appear, and the allowable parent/child relationships. Document Type Definition[edit] Main article: Document Type Definition The oldest schema language for XML
XML
is the Document Type Definition (DTD), inherited from SGML. DTDs have the following benefits:

DTD support is ubiquitous due to its inclusion in the XML
XML
1.0 standard. DTDs are terse compared to element-based schema languages and consequently present more information in a single screen. DTDs allow the declaration of standard public entity sets for publishing characters. DTDs define a document type rather than the types used by a namespace, thus grouping all constraints for a document in a single collection.

DTDs have the following limitations:

They have no explicit support for newer features of XML, most importantly namespaces. They lack expressiveness. XML
XML
DTDs are simpler than SGML
SGML
DTDs and there are certain structures that cannot be expressed with regular grammars. DTDs only support rudimentary datatypes. They lack readability. DTD designers typically make heavy use of parameter entities (which behave essentially as textual macros), which make it easier to define complex grammars, but at the expense of clarity. They use a syntax based on regular expression syntax, inherited from SGML, to describe the schema. Typical XML
XML
APIs such as SAX do not attempt to offer applications a structured representation of the syntax, so it is less accessible to programmers than an element-based syntax may be.

Two peculiar features that distinguish DTDs from other schema types are the syntactic support for embedding a DTD within XML
XML
documents and for defining entities, which are arbitrary fragments of text and/or markup that the XML
XML
processor inserts in the DTD itself and in the XML document wherever they are referenced, like character escapes. DTD technology is still used in many applications because of its ubiquity. XML
XML
Schema[edit] Main article: XML
XML
Schema (W3C) A newer schema language, described by the W3C
W3C
as the successor of DTDs, is XML
XML
Schema, often referred to by the initialism for XML Schema instances, XSD ( XML
XML
Schema Definition). XSDs are far more powerful than DTDs in describing XML
XML
languages. They use a rich datatyping system and allow for more detailed constraints on an XML document's logical structure. XSDs also use an XML-based format, which makes it possible to use ordinary XML
XML
tools to help process them. xs:schema element that defines a schema:

<?xml version="1.0" encoding="ISO-8859-1" ?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"></xs:schema>

RELAX NG[edit] RELAX NG (Regular Language
Language
for XML
XML
Next Generation) was initially specified by OASIS and is now a standard (Part 2: Regular-grammar-based validation of ISO/IEC 19757 - DSDL). RELAX NG schemas may be written in either an XML
XML
based syntax or a more compact non- XML
XML
syntax; the two syntaxes are isomorphic and James Clark's conversion tool—Trang—can convert between them without loss of information. RELAX NG has a simpler definition and validation framework than XML
XML
Schema, making it easier to use and implement. It also has the ability to use datatype framework plug-ins; a RELAX NG schema author, for example, can require values in an XML
XML
document to conform to definitions in XML
XML
Schema Datatypes. Schematron[edit] Schematron is a language for making assertions about the presence or absence of patterns in an XML
XML
document. It typically uses XPath expressions. Schematron is now a standard (Part 3: Rule-based validation of ISO/IEC 19757 - DSDL). DSDL and other schema languages[edit] DSDL (Document Schema Definition Languages) is a multi-part ISO/IEC standard (ISO/IEC 19757) that brings together a comprehensive set of small schema languages, each targeted at specific problems. DSDL includes RELAX NG full and compact syntax, Schematron assertion language, and languages for defining datatypes, character repertoire constraints, renaming and entity expansion, and namespace-based routing of document fragments to different validators. DSDL schema languages do not have the vendor support of XML
XML
Schemas yet, and are to some extent a grassroots reaction of industrial publishers to the lack of utility of XML
XML
Schemas for publishing. Some schema languages not only describe the structure of a particular XML
XML
format but also offer limited facilities to influence processing of individual XML
XML
files that conform to this format. DTDs and XSDs both have this ability; they can for instance provide the infoset augmentation facility and attribute defaults. RELAX NG and Schematron intentionally do not provide these. Related specifications[edit] A cluster of specifications closely related to XML
XML
have been developed, starting soon after the initial publication of XML
XML
1.0. It is frequently the case that the term "XML" is used to refer to XML together with one or more of these other technologies that have come to be seen as part of the XML
XML
core.

XML
XML
namespaces enable the same document to contain XML
XML
elements and attributes taken from different vocabularies, without any naming collisions occurring. Although XML
XML
Namespaces are not part of the XML specification itself, virtually all XML
XML
software also supports XML Namespaces. XML Base defines the xml:base attribute, which may be used to set the base for resolution of relative URI references within the scope of a single XML
XML
element. XML Information Set or XML
XML
Infoset is an abstract data model for XML documents in terms of information items. The infoset is commonly used in the specifications of XML
XML
languages, for convenience in describing constraints on the XML
XML
constructs those languages allow. XSL (Extensible Stylesheet Language) is a family of languages used to transform and render XML
XML
documents, split into three parts:

XSLT
XSLT
( XSL Transformations), an XML
XML
language for transforming XML documents into other XML
XML
documents or other formats such as HTML, plain text, or XSL-FO. XSLT
XSLT
is very tightly coupled with XPath, which it uses to address components of the input XML
XML
document, mainly elements and attributes. XSL-FO ( XSL Formatting Objects), an XML
XML
language for rendering XML documents, often used to generate PDFs. XPath
XPath
( XML
XML
Path Language), a non- XML
XML
language for addressing the components (elements, attributes, and so on) of an XML
XML
document. XPath is widely used in other core- XML
XML
specifications and in programming libraries for accessing XML-encoded data.

XQuery ( XML
XML
Query) is an XML
XML
query language strongly rooted in XPath and XML
XML
Schema. It provides methods to access, manipulate and return XML, and is mainly conceived as a query language for XML
XML
databases. XML Signature defines syntax and processing rules for creating digital signatures on XML
XML
content. XML Encryption defines syntax and processing rules for encrypting XML content. xml-model (Part 11: Schema Association of ISO/IEC 19757 - DSDL) defines a means of associating any xml document with any of the schema types mentioned above.

Some other specifications conceived as part of the " XML
XML
Core" have failed to find wide adoption, including XInclude, XLink, and XPointer. Programming interfaces[edit] The design goals of XML
XML
include, "It shall be easy to write programs which process XML
XML
documents."[5] Despite this, the XML
XML
specification contains almost no information about how programmers might go about doing such processing. The XML
XML
Infoset specification provides a vocabulary to refer to the constructs within an XML
XML
document, but does not provide any guidance on how to access this information. A variety of APIs for accessing XML
XML
have been developed and used, and some have been standardized. Existing APIs for XML
XML
processing tend to fall into these categories:

Stream-oriented APIs accessible from a programming language, for example SAX and StAX. Tree-traversal APIs accessible from a programming language, for example DOM. XML
XML
data binding, which provides an automated translation between an XML
XML
document and programming-language objects. Declarative transformation languages such as XSLT
XSLT
and XQuery. Syntax extensions to general-purpose programming languages, for example LINQ and Scala.

Stream-oriented facilities require less memory and, for certain tasks based on a linear traversal of an XML
XML
document, are faster and simpler than other alternatives. Tree-traversal and data-binding APIs typically require the use of much more memory, but are often found more convenient for use by programmers; some include declarative retrieval of document components via the use of XPath
XPath
expressions. XSLT
XSLT
is designed for declarative description of XML
XML
document transformations, and has been widely implemented both in server-side packages and Web browsers. XQuery overlaps XSLT
XSLT
in its functionality, but is designed more for searching of large XML
XML
databases. Simple API for XML[edit] Main article: Simple API for XML Simple API for XML (SAX) is a lexical, event-driven API in which a document is read serially and its contents are reported as callbacks to various methods on a handler object of the user's design. SAX is fast and efficient to implement, but difficult to use for extracting information at random from the XML, since it tends to burden the application author with keeping track of what part of the document is being processed. It is better suited to situations in which certain types of information are always handled the same way, no matter where they occur in the document. Pull parsing[edit] Pull parsing[21] treats the document as a series of items read in sequence using the iterator design pattern. This allows for writing of recursive descent parsers in which the structure of the code performing the parsing mirrors the structure of the XML
XML
being parsed, and intermediate parsed results can be used and accessed as local variables within the methods performing the parsing, or passed down (as method parameters) into lower-level methods, or returned (as method return values) to higher-level methods. Examples of pull parsers include Data::Edit::Xml https://metacpan.org/pod/Data::Edit::Xml in Perl, StAX in the Java programming language, XMLPullParser in Smalltalk, XMLReader in PHP, ElementTree.iterparse in Python, System.Xml.XmlReader in the .NET Framework, and the DOM traversal API (NodeIterator and TreeWalker). A pull parser creates an iterator that sequentially visits the various elements, attributes, and data in an XML
XML
document. Code that uses this iterator can test the current item (to tell, for example, whether it is a start-tag or end-tag, or text), and inspect its attributes (local name, namespace, values of XML
XML
attributes, value of text, etc.), and can also move the iterator to the next item. The code can thus extract information from the document as it traverses it. The recursive-descent approach tends to lend itself to keeping data as typed local variables in the code doing the parsing, while SAX, for instance, typically requires a parser to manually maintain intermediate data within a stack of elements that are parent elements of the element being parsed. Pull-parsing code can be more straightforward to understand and maintain than SAX parsing code. Document Object Model[edit] Main article: Document Object Model Document Object Model
Document Object Model
(DOM) is an API that allows for navigation of the entire document as if it were a tree of node objects representing the document's contents. A DOM document can be created by a parser, or can be generated manually by users (with limitations). Data types in DOM nodes are abstract; implementations provide their own programming language-specific bindings. DOM implementations tend to be memory intensive, as they generally require the entire document to be loaded into memory and constructed as a tree of objects before access is allowed. Data binding[edit] XML data binding is the binding of XML
XML
documents to a hierarchy of custom and strongly typed objects, in contrast to the generic objects created by a DOM parser. This approach simplifies code development, and in many cases allows problems to be identified at compile time rather than run-time. It is suitable for applications where the document structure is known and fixed at the time the application is written. Example data binding systems include the Java Architecture for XML
XML
Binding (JAXB), XML
XML
Serialization in .NET Framework.[22] and XML
XML
serialization in gSOAP. XML
XML
as data type[edit] XML
XML
has appeared as a first-class data type in other languages. The ECMAScript for XML
XML
(E4X) extension to the ECMAScript/JavaScript language explicitly defines two specific objects ( XML
XML
and XMLList) for JavaScript, which support XML
XML
document nodes and XML
XML
node lists as distinct objects and use a dot-notation specifying parent-child relationships.[23] E4X is supported by the Mozilla
Mozilla
2.5+ browsers (though now deprecated) and Adobe Actionscript, but has not been adopted more universally. Similar notations are used in Microsoft's LINQ implementation for Microsoft
Microsoft
.NET 3.5 and above, and in Scala (which uses the Java VM). The open-source xmlsh application, which provides a Linux-like shell with special features for XML manipulation, similarly treats XML
XML
as a data type, using the <[ ]> notation.[24] The Resource Description Framework
Resource Description Framework
defines a data type rdf:XMLLiteral to hold wrapped, canonical XML.[25] Facebook has produced extensions to the PHP
PHP
and JavaScript
JavaScript
languages that add XML to the core syntax in a similar fashion to E4X, namely XHP and JSX respectively. History[edit] XML
XML
is an application profile of SGML
SGML
(ISO 8879).[26] The versatility of SGML
SGML
for dynamic information display was understood by early digital media publishers in the late 1980s prior to the rise of the Internet.[27][28] By the mid-1990s some practitioners of SGML had gained experience with the then-new World Wide Web, and believed that SGML
SGML
offered solutions to some of the problems the Web was likely to face as it grew. Dan Connolly added SGML
SGML
to the list of W3C's activities when he joined the staff in 1995; work began in mid-1996 when Sun Microsystems
Sun Microsystems
engineer Jon Bosak
Jon Bosak
developed a charter and recruited collaborators. Bosak was well connected in the small community of people who had experience both in SGML
SGML
and the Web.[29] XML
XML
was compiled by a working group of eleven members,[30] supported by a (roughly) 150-member Interest Group. Technical debate took place on the Interest Group mailing list and issues were resolved by consensus or, when that failed, majority vote of the Working Group. A record of design decisions and their rationales was compiled by Michael Sperberg-McQueen
Michael Sperberg-McQueen
on December 4, 1997.[31] James Clark served as Technical Lead of the Working Group, notably contributing the empty-element "<empty />" syntax and the name "XML". Other names that had been put forward for consideration included "MAGMA" (Minimal Architecture for Generalized Markup Applications), "SLIM" (Structured Language
Language
for Internet
Internet
Markup) and "MGML" (Minimal Generalized Markup Language). The co-editors of the specification were originally Tim Bray
Tim Bray
and Michael Sperberg-McQueen. Halfway through the project Bray accepted a consulting engagement with Netscape, provoking vociferous protests from Microsoft. Bray was temporarily asked to resign the editorship. This led to intense dispute in the Working Group, eventually solved by the appointment of Microsoft's Jean Paoli as a third co-editor. The XML
XML
Working Group never met face-to-face; the design was accomplished using a combination of email and weekly teleconferences. The major design decisions were reached in a short burst of intense work between August and November 1996,[32] when the first Working Draft of an XML
XML
specification was published.[33] Further design work continued through 1997, and XML
XML
1.0 became a W3C
W3C
Recommendation on February 10, 1998. Sources[edit] XML
XML
is a profile of an ISO standard SGML, and most of XML
XML
comes from SGML
SGML
unchanged. From SGML
SGML
comes the separation of logical and physical structures (elements and entities), the availability of grammar-based validation (DTDs), the separation of data and metadata (elements and attributes), mixed content, the separation of processing from representation (processing instructions), and the default angle-bracket syntax. Removed were the SGML
SGML
declaration ( XML
XML
has a fixed delimiter set and adopts Unicode
Unicode
as the document character set). Other sources of technology for XML
XML
were the TEI (Text Encoding Initiative), which defined a profile of SGML
SGML
for use as a "transfer syntax"; and HTML, in which elements were synchronous with their resource, document character sets were separate from resource encoding, the xml:lang attribute was invented, and (like HTTP) metadata accompanied the resource rather than being needed at the declaration of a link. The ERCS(Extended Reference Concrete Syntax) project of the SPREAD (Standardization Project Regarding East Asian Documents) project of the ISO-related China/Japan/Korea Document Processing expert group was the basis of XML
XML
1.0's naming rules; SPREAD also introduced hexadecimal numeric character references and the concept of references to make available all Unicode
Unicode
characters. To support ERCS, XML
XML
and HTML
HTML
better, the SGML
SGML
standard IS 8879 was revised in 1996 and 1998 with Web SGML
SGML
Adaptations. The XML
XML
header followed that of ISO HyTime. Ideas that developed during discussion that are novel in XML
XML
included the algorithm for encoding detection and the encoding header, the processing instruction target, the xml:space attribute, and the new close delimiter for empty-element tags. The notion of well-formedness as opposed to validity (which enables parsing without a schema) was first formalized in XML, although it had been implemented successfully in the Electronic Book Technology "Dynatext" software;[34] the software from the University of Waterloo New Oxford English Dictionary Project; the RISP LISP SGML
SGML
text processor at Uniscope, Tokyo; the US Army Missile Command IADS hypertext system; Mentor Graphics Context; Interleaf and Xerox Publishing
Publishing
System. Versions[edit] There are two current versions of XML. The first ( XML
XML
1.0) was initially defined in 1998. It has undergone minor revisions since then, without being given a new version number, and is currently in its fifth edition, as published on November 26, 2008. It is widely implemented and still recommended for general use. The second ( XML
XML
1.1) was initially published on February 4, 2004, the same day as XML
XML
1.0 Third Edition,[35] and is currently in its second edition, as published on August 16, 2006. It contains features (some contentious) that are intended to make XML
XML
easier to use in certain cases.[36] The main changes are to enable the use of line-ending characters used on EBCDIC
EBCDIC
platforms, and the use of scripts and characters absent from Unicode
Unicode
3.2. XML
XML
1.1 is not very widely implemented and is recommended for use only by those who need its particular features.[37] Prior to its fifth edition release, XML
XML
1.0 differed from XML
XML
1.1 in having stricter requirements for characters available for use in element and attribute names and unique identifiers: in the first four editions of XML
XML
1.0 the characters were exclusively enumerated using a specific version of the Unicode
Unicode
standard ( Unicode
Unicode
2.0 to Unicode
Unicode
3.2.) The fifth edition substitutes the mechanism of XML
XML
1.1, which is more future-proof but reduces redundancy. The approach taken in the fifth edition of XML
XML
1.0 and in all editions of XML
XML
1.1 is that only certain characters are forbidden in names, and everything else is allowed to accommodate suitable name characters in future Unicode
Unicode
versions. In the fifth edition, XML
XML
names may contain characters in the Balinese, Cham, or Phoenician scripts among many others added to Unicode
Unicode
since Unicode
Unicode
3.2.[36] Almost any Unicode
Unicode
code point can be used in the character data and attribute values of an XML
XML
1.0 or 1.1 document, even if the character corresponding to the code point is not defined in the current version of Unicode. In character data and attribute values, XML
XML
1.1 allows the use of more control characters than XML
XML
1.0, but, for "robustness", most of the control characters introduced in XML
XML
1.1 must be expressed as numeric character references (and #x7F through #x9F, which had been allowed in XML
XML
1.0, are in XML
XML
1.1 even required to be expressed as numeric character references[38]). Among the supported control characters in XML
XML
1.1 are two line break codes that must be treated as whitespace. Whitespace characters are the only control codes that can be written directly. There has been discussion of an XML
XML
2.0, although no organization has announced plans for work on such a project. XML-SW (SW for skunkworks), written by one of the original developers of XML,[39] contains some proposals for what an XML
XML
2.0 might look like: elimination of DTDs from syntax, integration of namespaces, XML
XML
Base and XML Information Set into the base standard. The World Wide Web Consortium
World Wide Web Consortium
also has an XML
XML
Binary Characterization Working Group doing preliminary research into use cases and properties for a binary encoding of XML
XML
Information Set. The working group is not chartered to produce any official standards. Since XML
XML
is by definition text-based, ITU-T and ISO are using the name Fast Infoset for their own binary infoset to avoid confusion (see ITU-T Rec. X.891 and ISO/IEC 24824-1). Criticism[edit] XML
XML
and its extensions have regularly been criticized for verbosity and complexity.[40] Mapping the basic tree model of XML
XML
to type systems of programming languages or databases can be difficult, especially when XML
XML
is used for exchanging highly structured data between applications, which was not its primary design goal. However, XML data binding systems allow applications to access XML
XML
data directly from objects representing a data structure of the data in the programming language used, which ensures type safety, rather than using the DOM or SAX to retrieve data from a direct representation of the XML
XML
itself. This is accomplished by automatically creating a mapping between elements of the XML schema XSD of the document and members of a class to be represented in memory. Other criticisms attempt to refute the claim that XML
XML
is a self-describing language[41] (though the XML
XML
specification itself makes no such claim). JSON, YAML, and S-Expressions are frequently proposed as simpler alternatives (see Comparison of data serialization formats);[42] that focus on representing highly structured data rather than documents, which may contain both highly structured and relatively unstructured content. However, W3C
W3C
standardized XML schema specifications offer a broader range of structured XSD data types compared to simpler serialization formats and offer modularity and reuse through XML
XML
namespace. See also[edit]

List of XML
XML
markup languages List of XML
XML
schemas Comparison of layout engines (XML) Comparison of data serialization formats Binary XML EBML WBXML XHTML XML
XML
Protocol

Notes[edit]

^ Murata, Kohn & Lilley (2009), in their draft RFC to update RFC 3023 (2001) that introduced text/xml, and advocated its formal deprecation.[9] However RFC:7203 (2014) did not do this. ^ i.e., embedded quote characters would be a problem ^ A common example of this is CSS
CSS
class or identifier names.

References[edit]

^ " XML
XML
Media Types, RFC 7303". Internet
Internet
Engineering Task Force. July 2014.  ^ " XML
XML
1.0 Specification". World Wide Web
World Wide Web
Consortium. Retrieved 22 August 2010.  ^ " XML
XML
and Semantic Web W3C
W3C
Standards Timeline" (PDF). Dblab.ntua.gr. Retrieved 14 August 2016.  ^ " W3C
W3C
DOCUMENT LICENSE". W3.org. Retrieved 16 November 2017.  ^ a b " XML
XML
1.0 Origin and Goals". W3.org. Retrieved 14 August 2016.  ^ Fennell, Philip (June 2013). "Extremes of XML". XML
XML
London 2013: 80–86. doi:10.14337/XMLLondon13.Fennell01. ISBN 978-0-9926471-0-0.  ^ " XML
XML
Applications and Initiatives". Xml.coverages.org. Retrieved 16 November 2017.  ^ "appleexaminer.com: "PLIST files"". The Apple Examiner. Retrieved 16 November 2017.  ^ a b M. Murata; D. Kohn & C. Lilley (24 September 2009). " Internet
Internet
Drafts: XML
XML
Media Types". Internet
Internet
Engineering Task Force. Retrieved 29 February 2012.  ^ "Extensible Markup Language
Language
(XML) 1.0 (Fifth Edition)". World Wide Web Consortium. 2008-11-26. Retrieved 23 November 2012.  ^ "Extensible Markup Language
Language
(XML) 1.1 (Second Edition)". World Wide Web Consortium. Retrieved 22 August 2010.  ^ "Characters vs. Bytes". Tbray.org. Retrieved 16 November 2017.  ^ "Autodetection of Character Encodings". W3.org. Retrieved 16 November 2017.  ^ "Extensible Markup Language
Language
(XML) 1.0 (Fifth Edition)". W3.org. Retrieved 16 November 2017.  ^ " W3C
W3C
I18N FAQ: HTML, XHTML, XML
XML
and Control Codes". W3.org. Retrieved 16 November 2017.  ^ "Extensible Markup Language
Language
(XML)". W3.org. Retrieved 16 November 2017.  Section "Comments" ^ Pilgrim, Mark (2004). "The history of draconian error handling in XML". Web.archive.org. Archived from the original on 2011-07-26. Retrieved 18 July 2013.  ^ "There are no exceptions to Postel's Law [dive into mark]". Web.archive.org. Archived from the original on 2011-05-14. Retrieved 22 April 2013.  ^ " XML
XML
Notepad". Xmlnotepad/codeplex.com. Retrieved 16 November 2017.  ^ " XML
XML
Notepad 2007". Microsoft.com. Retrieved 16 November 2017.  ^ DuCharme, Bob. "Push, Pull, Next!". Xml.com. Retrieved 16 November 2017.  ^ " XML
XML
Serialization in the .NET Framework". Msdn.microsoft.com. Retrieved 31 July 2009.  ^ "Processing XML
XML
with E4X". Mozilla
Mozilla
Developer Center. Mozilla Foundation.  ^ " XML
XML
Shell: Core Syntax". Xmlsh.org. 2010-05-13. Retrieved 22 August 2010.  ^ " Resource Description Framework
Resource Description Framework
(RDF): Concepts and Abstract Syntax". W3.org. Retrieved 22 August 2010.  ^ "ISO/IEC 19757-3". ISO/IEC. 1 June 2006: vi.  ^ Bray, Tim (February 2005). "A conversation with Tim Bray: Searching for ways to tame the world's vast stores of information". Association for Computing
Computing
Machinery's "Queue site". Retrieved 16 April 2006.  ^ edited by Sueann Ambron; Kristina Hooper & foreword by John Sculley. (1988). "Publishers, multimedia, and interactivity". Interactive multimedia. Cobb Group. ISBN 1-55615-124-1. CS1 maint: Extra text: authors list (link) ^ Eliot Kimber (2006). " XML
XML
is 10". Drmacros-xml-rants.blogspot.com. Retrieved 16 November 2017.  ^ The working group was originally called the "Editorial Review Board." The original members and seven who were added before the first edition was complete, are listed at the end of the first edition of the XML
XML
Recommendation, at http://www.w3.org/TR/1998/REC-xml-19980210. ^ "Reports From the W3C
W3C
SGML
SGML
ERB to the SGML
SGML
WG And from the W3C
W3C
XML ERB to the XML
XML
SIG". W3.org. Retrieved 31 July 2009.  ^ "Oracle Technology Network for Java Developers - Oracle Technology Network - Oracle". Java.sun.com. Retrieved 16 November 2017.  ^ "Extensible Markup Language
Language
(XML)". W3.org. 1996-11-14. Retrieved 31 July 2009.  ^ Jon Bosak; Sun Microsystems
Sun Microsystems
(2006-12-07). "Closing Keynote, XML 2006". 2006.xmlconference.org. Archived from the original on 2007-07-11. Retrieved 31 July 2009.  ^ "Extensible Markup Language
Language
(XML) 1.0 (Third Edition)". W3.org. Retrieved 22 August 2010.  ^ a b "Extensible Markup Language
Language
(XML) 1.1 (Second Edition) , Rationale and list of changes for XML
XML
1.1". W3.org. Retrieved 20 January 2012.  ^ Harold, Elliotte Rusty (2004). Effective XML. Addison-Wesley. pp. 10–19. ISBN 0-321-15040-6.  ^ "Extensible Markup Language
Language
(XML) 1.1 (Second Edition)". W3.org. Retrieved 22 August 2010.  ^ Tim Bray: Extensible Markup Language, SW (XML-SW). 2002-02-10 ^ "XML: The Angle Bracket Tax". Codinghorror.com. Retrieved 16 November 2017.  ^ "The Myth of Self-Describing XML" (PDF). Workflow.healthbase.info. September 2003. Retrieved 16 November 2017.  ^ "What usable alternatives to XML
XML
syntax do you know?". Stackoverflow.com. Retrieved 16 November 2017. 

Further reading[edit]

Annex A of ISO 8879:1986 (SGML) Lawrence A. Cunningham (2005). "Language, Deals and Standards: The Future of XML
XML
Contracts". Washington University Law Review. SSRN 900616 .  Bosak, Jon; Bray, Tim (May 1999). " XML
XML
and the Second-Generation Web". Scientific American. Archived from the original on 1 October 2009.  Kelly, Sean (February 6, 2006). "Making Mistakes with XML". Developer.com. Retrieved 26 October 2010.  St. Laurent, Simon (February 12, 2003). "Five years later, XML." O'Reilly XML
XML
Blog. O'Reilly Media. Retrieved 26 October 2010.  " W3C
W3C
XML
XML
is Ten!". World Wide Web
World Wide Web
Consortium. 12 February 2008. Retrieved 26 October 2010.  "Introduction to XML" (PDF). Course Slides. Pierre Geneves. October 2012. Archived from the original on 2015-10-16. CS1 maint: BOT: original-url status unknown (link)

External links[edit]

Wikimedia Commons has media related to XML.

Wikibooks has a book on the topic of: Subject:XML

W3C
W3C
XML
XML
homepage XML
XML
1.0 Specification Retrospective on Extended Reference Concrete Syntax by Rick Jelliffe XML, Java and the Future of the Web (1997) by Jon Bosak http://validator.w3.org/ The Official [W3C] Markup Validation Service The XML
XML
FAQ originally for the W3C's XML
XML
SIG by Peter Flynn

v t e

World Wide Web Consortium
World Wide Web Consortium
(W3C)

Products and standards

Recommendations

ActivityPub ARIA Canonical XML CDF CSS DOM Geolocation API HTML
HTML
(HTML5) ITS JSON-LD Linked Data Notifications MathML Micropub OWL P3P PLS RDF RDF Schema SISR SKOS SMIL SOAP SRGS SRI SSML SVG SCXML SPARQL Timed text VoiceXML Web storage WSDL Webmention WebSub XForms XHTML XHTML+RDFa XInclude XLink XML XML
XML
Base XML
XML
Encryption XML
XML
Events XML
XML
Information Set XML
XML
namespace XML
XML
Schema XML
XML
Signature XOP XPath XPath
XPath
2.0 XPointer XProc XQuery XSL XSL-FO XSLT (elements)

Notes

IndieAuth JF2 Post Type Discovery XAdES XHTML+SMIL XUP

Working drafts

CCXML CURIE EME InkML MSE RIF SMIL Timesheets sXBL WICD XFDL XFrames XBL XMLHttpRequest

Guidelines

Web Content Accessibility Guidelines

Initiative

Multimodal Interaction Activity (MMI) Markup Validation Service Web Accessibility Initiative WebPlatform

Deprecated

C-HTML HDML JSSS PGML VML XHTML+MathML+SVG

Organizations

Advisory Committee (AC) World Wide Web
World Wide Web
Foundation

Elected groups

Advisory Board (AB) Technical Architecture Group (TAG)

Working groups

CSS Geolocation Social Web SVG Web Hypertext Application Technology (WHATWG) Web Platform

Closed groups

Device Description (DDWG) HTML WebOnt (Semantic Web Activity)

Software

CERN httpd Libwww

Browsers

Line Mode (1990–) Arena (1993–98) Agora (1994–97) Argo (1994–97) Amaya (browser/editor, 1996–2012)

Conferences

International World Wide Web
World Wide Web
Conference (IW3C)

Steering Committee (IW3C2) First conference ("WWW1", 1994)

v t e

Web browsers

Comparison

lightweight

History List

for Unix

Timeline Usage share

Features

Ad filtering Augmented browsing Bookmarks

Bookmarklet Live bookmark Smart Bookmarks

Browser extension Browser security Browser synchronizer

comparison

Cookies Download manager Favicon Incremental search Plug-in Privacy mode Tabs Universal Edit Button

Web standards

Acid tests Cascading Style Sheets HTML HTML5 JavaScript MathML SVG WebGL XHTML

Protocols

HTTP HTTPS OCSP SPDY SSL/TLS WebSocket WPAD

Related topics

BrowserChoice.eu CRL iLoo Internet
Internet
suite Man-in-the-browser Mobile Web Offline reader PAC Pwn2Own Rich Internet
Internet
application Site-specific browser Widget World Wide Web XML

Desktop

Blink-based

Brave Chrome Chromium Dragon Falkon Opera Sleipnir Slimjet SRWare Iron UC Browser Vivaldi Yandex Browser Sputnik SafeZone Whale

Gecko-based

AT&T Pogo Avant Camino Firefox

Conkeror GNU IceCat IceDragon Swiftfox Swiftweasel TenFourFox Timberwolf Tor Browser Waterfox xB Browser

Galeon Ghostzilla Goanna

Basilisk Pale Moon

K-Meleon Kazehakase Kirix Strata Lotus Symphony Lunascape Mozilla

Beonex Communicator Classilla Netscape SeaMonkey

Trident-based

AOL Explorer Avant Deepnet Explorer GreenBrowser Internet
Internet
Explorer Lunascape Maxthon MediaBrowser MenuBox NeoPlanet NetCaptor SlimBrowser SpaceTime UltraBrowser WebbIE ZAC Browser

WebKit-based

Arora Avant Dooble Epic Flock Fluid iCab Konqueror Lunascape Maxthon Midori OmniWeb Origyn Web Browser Otter Browser QtWeb rekonq Safari Shiira SlimBoat surf Torch Uzbl Epiphany WebPositive xombrero

Text-based

ELinks Emacs/W3 Line Mode Browser Links Lynx w3m

Other

abaco Amaya Arachne Arena Charon Dillo eww Gazelle HotJava IBM Home Page Reader IBrowse KidZui Microsoft
Microsoft
Edge Mosaic Mothra NetPositive NetSurf Qihoo 360 Secure Browser

Mobile

Blink-based

Android Browser Chromium

Brave Chrome for Android Opera Mobile Silk

Firefox
Firefox
Focus for Android

Gecko-based

Firefox
Firefox
for Android MicroB Minimo Waterfox

WebKit-based

BOLT Dolphin Browser Chrome for iOS Firefox
Firefox
for iOS Firefox
Firefox
Focus for iOS Maxthon Mercury Browser Nokia Browser for Symbian Opera Coast Rockmelt Safari Steel

Other

Blazer CM Browser Deepfish Internet
Internet
Explorer Mobile Iris Browser Konqueror
Konqueror
Embedded Microsoft
Microsoft
Edge NetFront Opera Mini Skweezer Skyfire Teashark ThunderHawk UC Browser Vision WinWAP

Television and video game console

Gecko-based

Kylo

Presto-based

Internet
Internet
Channel

WebKit-based

Google TV Nintendo 3DS Internet
Internet
Browser Nintendo DS & DSi Browser NetFront Steam Overlay Wii U Internet
Internet
Browser

Other

MSN TV

Software no longer in development shown in italics

Category Commons Internet
Internet
portal Software portal

v t e

Data exchange formats

Human readable formats

Atom XML YAML JSON RDF Rebol RSS OWL

Binary formats

AMF ASN.1

SMI

Avro BSON CBOR FlatBuffers MessagePack Protocol Buffers Thrift Smile XDR

Authority control

LCCN: sh97007825 GND: 4501553-3 BNF: cb131774360 (d

.