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49-484: XSD ( XML Schema Definition ), a recommendation of the World Wide Web Consortium ( W3C ), specifies how to formally describe the elements in an Extensible Markup Language ( XML ) document. It can be used by programmers to verify each piece of item content in a document, to assure it adheres to the description of the element it is placed in. Like all XML schema languages , XSD can be used to express

98-682: A W3C Recommendation in April 2012 , which means it is an approved W3C specification. Significant new features in XSD 1.1 are: Until the Proposed Recommendation draft, XSD 1.1 also proposed the addition of a new numeric data type, precisionDecimal. This proved controversial, and was therefore dropped from the specification at a late stage of development. W3C XML Schema 1.0 Specification W3C XML Schema 1.1 Specification Other W3C The World Wide Web Consortium ( W3C )

147-612: A W3C recommendation in May 2001, is one of several XML schema languages . It was the first separate schema language for XML to achieve Recommendation status by the W3C. Because of confusion between XML Schema as a specific W3C specification, and the use of the same term to describe schema languages in general, some parts of the user community referred to this language as WXS , an initialism for W3C XML Schema, while others referred to it as XSD , an initialism for XML Schema Definition. In Version 1.1

196-499: A programming language ( built-in types ). Data types which are not primitive are referred to as derived or composite . Primitive types are almost always value types , but composite types may also be value types. The most common primitive types are those used and supported by computer hardware, such as integers of various sizes, floating-point numbers, and Boolean logical values. Operations on such types are usually quite efficient. Primitive data types which are native to

245-461: A built-in type and true and false as reserved words. The Java virtual machine's set of primitive data types consists of: The set of basic C data types is similar to Java's. Minimally, there are four types, char , int , float , and double , but the qualifiers short , long , signed , and unsigned mean that C contains numerous target-dependent integer and floating-point primitive types. C99 extended this set by adding

294-753: A community of major web players and publishers to establish a MediaWiki wiki that seeks to document open web standards called the WebPlatform and WebPlatform Docs. In January 2013, Beihang University became the Chinese host. In 2022 the W3C WebFonts Working Group won an Emmy Award from the National Academy of Television Arts and Sciences for standardizing font technology for custom downloadable fonts and typography for web and TV devices. On 1 January 2023, it reformed as

343-520: A complex type may be constrained by assertions— XPath 2.0 expressions evaluated against the content that must evaluate to true. After XML Schema-based validation, it is possible to express an XML document's structure and content in terms of the data model that was implicit during validation. The XML Schema data model includes: This collection of information is called the Post-Schema-Validation Infoset (PSVI). The PSVI gives

392-459: A format equivalent to scientific notation , typically in binary but sometimes in decimal . Because floating-point numbers have limited precision, only a subset of real or rational numbers are exactly representable; other numbers can be represented only approximately. Many languages have both a single precision (often called float ) and a double precision type (often called double ). A Boolean type , typically denoted bool or boolean ,

441-481: A length of one are normally used to represent single characters. Some languages have character types that are too small to represent all Unicode characters. These are more properly categorized as integer types that have been given a misleading name. For example C includes a char type, but it is defined to be the smallest addressable unit of memory, which several standards (such as POSIX ) require to be 8 bits . Recent versions of these standards refer to char as

490-561: A new edition or level of the recommendation. Additionally, the W3C publishes various kinds of informative notes which are to be used as references. Unlike the Internet Society and other international standards bodies, the W3C does not have a certification program. The W3C has decided, for now, that it is not suitable to start such a program, owing to the risk of creating more drawbacks for the community than benefits. In January 2023, after 28 years of being jointly administered by

539-462: A public-interest 501(c)(3) non-profit organization . W3C develops technical specifications for HTML5 , CSS , SVG , WOFF , the Semantic Web stack , XML , and other technologies. Sometimes, when a specification becomes too large, it is split into independent modules that can mature at their own pace. Subsequent editions of a module or specification are known as levels and are denoted by

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588-435: A set of schema components : chiefly element and attribute declarations and complex and simple type definitions. These components are usually created by processing a collection of schema documents , which contain the source language definitions of these components. In popular usage, however, a schema document is often referred to as a schema. Schema documents are organized by namespace: all the named schema components belong to

637-418: A set of basic data types from which all other data types are constructed. Specifically it often refers to the limited set of data representations in use by a particular processor , which all compiled programs must use. Most processors support a similar set of primitive data types, although the specific representations vary. More generally, primitive data types may refer to the standard data types built into

686-597: A set of core principles and components that are chosen by the consortium. It was originally intended that CERN host the European branch of W3C; however, CERN wished to focus on particle physics , not information technology . In April 1995, the French Institute for Research in Computer Science and Automation became the European host of W3C, with Keio University Research Institute at SFC becoming

735-442: A set of rules to which an XML document must conform to be considered "valid" according to that schema. However, unlike most other schema languages, XSD was also designed with the intent that determination of a document's validity would produce a collection of information adhering to specific data types . Such a post-validation infoset can be useful in the development of XML document processing software. XML Schema , published as

784-404: A target namespace, and the target namespace is a property of the schema document as a whole. A schema document may include other schema documents for the same namespace, and may import schema documents for a different namespace. When an instance document is validated against a schema (a process known as assessment ), the schema to be used for validation can either be supplied as a parameter to

833-468: A valid XML document its "type" and facilitates treating the document as an object, using object-oriented programming (OOP) paradigms. The primary reason for defining an XML schema is to formally describe an XML document; however the resulting schema has a number of other uses that go beyond simple validation. The schema can be used to generate code, referred to as XML Data Binding . This code allows contents of XML documents to be treated as objects within

882-548: A while after XML Schema was published. A number of Microsoft products supported XDR until the release of MSXML 6.0 (which dropped XDR in favor of XML Schema) in December 2006. Commerce One , Inc. supported its SOX schema language until declaring bankruptcy in late 2004. The most obvious features offered in XSD that are not available in XML's native Document Type Definitions (DTDs) are namespace awareness and datatypes, that is,

931-462: A working draft (WD) for review by the community. A WD document is the first form of a standard that is publicly available. Commentary by virtually anyone is accepted, though no promises are made with regard to action on any particular element commented upon. At this stage, the standard document may have significant differences from its final form. As such, anyone who implements WD standards should be ready to significantly modify their implementations as

980-458: Is a type that can represent all Unicode characters , hence must be at least 21 bits wide. Some languages such as Julia include a true 32-bit Unicode character type as primitive. Other languages such as JavaScript , Python , Ruby , and many dialects of BASIC do not have a primitive character type but instead add strings as a primitive data type, typically using the UTF-8 encoding. Strings with

1029-403: Is done by external experts in the W3C's various working groups. The Consortium is governed by its membership. The list of members is available to the public. Members include businesses, nonprofit organizations, universities, governmental entities, and individuals. Membership requirements are transparent except for one requirement: An application for membership must be reviewed and approved by

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1078-428: Is faster using SIMD operations and data types to operate on an array of floats. An integer data type represents some range of mathematical integers. Integers may be either signed (allowing negative values) or unsigned ( non-negative integers only). Common ranges are: A floating-point number represents a limited-precision rational number that may have a fractional part. These numbers are stored internally in

1127-555: Is now endorsed by the W3C, indicating its readiness for deployment to the public, and encouraging more widespread support among implementors and authors. Recommendations can sometimes be implemented incorrectly, partially, or not at all, but many standards define two or more levels of conformance that developers must follow if they wish to label their product as W3C-compliant. A recommendation may be updated or extended by separately-published, non-technical errata or editor drafts until sufficient substantial edits accumulate for producing

1176-437: Is successful in that it has been widely adopted and largely achieves what it set out to, it has been the subject of a great deal of severe criticism, perhaps more so than any other W3C Recommendation. Good summaries of the criticisms are provided by James Clark, Anders Møller and Michael Schwartzbach, Rick Jelliffe and David Webber. General problems: Practical limitations of expressibility: Technical problems: XSD 1.1 became

1225-569: Is the main international standards organization for the World Wide Web . Founded in 1994 and led by Tim Berners-Lee , the consortium is made up of member organizations that maintain full-time staff working together in the development of standards for the World Wide Web. As of 5 March 2023, W3C had 462 members. W3C also engages in education and outreach, develops software and serves as an open forum for discussion about

1274-571: Is the version of a standard that has passed the prior two levels. The users of the standard provide input. At this stage, the document is submitted to the W3C Advisory Council for final approval. While this step is important, it rarely causes any significant changes to a standard as it passes to the next phase. This is the most mature stage of development. At this point, the standard has undergone extensive review and testing, under both theoretical and practical conditions. The standard

1323-594: Is typically a logical type that can have either the value true or the value false . Although only one bit is necessary to accommodate the value set true and false , programming languages typically implement Boolean types as one or more bytes. Many languages (e.g. Java , Pascal and Ada ) implement Booleans adhering to the concept of Boolean as a distinct logical type. Some languages, though, may implicitly convert Booleans to numeric types at times to give extended semantics to Booleans and Boolean expressions or to achieve backwards compatibility with earlier versions of

1372-493: The Electronic Frontier Foundation 's resignation from W3C. As feared by the opponents of EME, as of 2020 , none of the widely used Content Decryption Modules used with EME are available for licensing without a per-browser licensing fee. W3C/ Internet Engineering Task Force standards (over Internet protocol suite ): Primitive data type In computer science , primitive data types are

1421-1040: The MIT Computer Science and Artificial Intelligence Laboratory (located in Stata Center ) in the United States, the (in Sophia Antipolis , France), Keio University (in Japan) and Beihang University (in China), the W3C incorporated as a legal entity, becoming a public-interest not-for-profit organization . The W3C has a staff team of 70–80 worldwide as of 2015 . W3C is run by a management team which allocates resources and designs strategy, led by CEO Jeffrey Jaffe (as of March 2010), former CTO of Novell . It also includes an advisory board that supports strategy and legal matters and helps resolve conflicts. The majority of standardization work

1470-686: The Asian host in September 1996. Starting in 1997, W3C created regional offices around the world. As of September 2009, it had eighteen World Offices covering Australia, the Benelux countries (Belgium, Netherlands and Luxembourg), Brazil, China, Finland, Germany, Austria, Greece, Hong Kong, Hungary, India, Israel, Italy, South Korea, Morocco, South Africa, Spain, Sweden, and, as of 2016, the United Kingdom and Ireland. In October 2012, W3C convened

1519-591: The Boolean type _Bool and allowing the modifier long to be used twice in combination with int (e.g. long long int ). The XML Schema Definition language provides a set of 19 primitive data types: In JavaScript, there are 7 primitive data types: string, number, bigint, boolean, symbol, undefined, and null. Their values are considered immutable . These are not objects and have no methods or properties ; however, all primitives except undefined and null have object wrappers . In Visual Basic .NET ,

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1568-429: The W3C has chosen to adopt XSD as the preferred name, and that is the name used in this article. In its appendix of references, the XSD specification acknowledges the influence of DTDs and other early XML schema efforts such as DDML , SOX , XML-Data, and XDR . It has adopted features from each of these proposals but is also a compromise among them. Of those languages, XDR and SOX continued to be used and supported for

1617-453: The W3C started considering adding DRM -specific Encrypted Media Extensions (EME) to HTML5 , which was criticised as being against the openness, interoperability, and vendor neutrality that distinguished websites built using only W3C standards from those requiring proprietary plug-ins like Flash . On 18 September 2017, the W3C published the EME specification as a recommendation, leading to

1666-522: The W3C. Many guidelines and requirements are stated in detail, but there is no final guideline about the process or standards by which membership might be finally approved or denied. The cost of membership is given on a sliding scale, depending on the character of the organization applying and the country in which it is located. Countries are categorized by the World Bank 's most recent grouping by gross national income per capita. In 2012 and 2013,

1715-885: The Web. The World Wide Web Consortium (W3C) was founded in 1994 by Tim Berners-Lee after he left the European Organization for Nuclear Research ( CERN ) in October 1994. It was founded at the Massachusetts Institute of Technology (MIT) Laboratory for Computer Science with support from the European Commission , and the Defense Advanced Research Projects Agency , which had pioneered the ARPANET ,

1764-399: The ability to define element and attribute content as containing values such as integers and dates rather than arbitrary text. The XSD 1.0 specification was originally published in 2001, with a second edition following in 2004 to correct large numbers of errors. XSD 1.1 became a W3C Recommendation in April 2012 . Technically, a schema is an abstract collection of metadata, consisting of

1813-413: The filename extension ".xsd". A unique Internet Media Type is not yet registered for XSDs, so "application/xml" or "text/xml" should be used, as per RFC 3023. The main components of a schema are: Other more specialized components include annotations, assertions, notations, and the schema component which contains information about the schema as a whole. Simple types (also called data types) constrain

1862-455: The first integer in the title (e.g. CSS3 = Level 3). Subsequent revisions on each level are denoted by an integer following a decimal point (for example, CSS2.1 = Revision 1). The W3C standard formation process is defined within the W3C process document, outlining four maturity levels through which each new standard or recommendation must progress. After enough content has been gathered from 'editor drafts' and discussion, it may be published as

1911-467: The language. For example, early versions of the C programming language that followed ANSI C and its former standards did not have a dedicated Boolean type. Instead, numeric values of zero are interpreted as false , and any other value is interpreted as true . The newer C99 added a distinct Boolean type _Bool (the more intuitive name bool as well as the macros true and false can be included with stdbool.h ), and C++ supports bool as

1960-729: The most direct predecessor to the modern Internet . It was located in Technology Square until 2004, when it moved, with the MIT Computer Science and Artificial Intelligence Laboratory, to the Stata Center. The organization tries to foster compatibility and agreement among industry members in the adoption of new standards defined by the W3C. Incompatible versions of HTML are offered by different vendors, causing inconsistency in how web pages are displayed. The consortium tries to get all those vendors to implement

2009-451: The permitted content of an element, including its element and text children and its attributes. A complex type definition consists of a set of attribute uses and a content model. Varieties of content model include: A complex type can be derived from another complex type by restriction (disallowing some elements, attributes, or values that the base type permits) or by extension (allowing additional attributes and elements to appear). In XSD 1.1,

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2058-498: The primitive data types consist of 4 integral types, 2 floating-point types, a 16-byte decimal type, a Boolean type, a date/time type, a Unicode character type, and a Unicode string type. Rust has primitive unsigned and signed fixed width integers in the format u or i respectively followed by any bit width that is a power of two between 8 and 128 giving the types u8 , u16 , u32 , u64 , u128 , i8 , i16 , i32 , i64 and i128 . Also available are

2107-420: The processor have a one-to-one correspondence with objects in the computer's memory, and operations on these types are often the fastest possible in most cases. Integer addition, for example, can be performed as a single machine instruction, and some offer specific instructions to process sequences of characters with a single instruction. But the choice of primitive data type may affect performance, for example it

2156-469: The programming environment. The schema can be used to generate human-readable documentation of an XML file structure; this is especially useful where the authors have made use of the annotation elements. No formal standard exists for documentation generation, but a number of tools are available, such as the Xs3p stylesheet, that will produce high-quality readable HTML and printed material. Although XML Schema

2205-470: The specification itself, and further derived types can be defined by users in their own schemas. The mechanisms available for restricting data types include the ability to specify minimum and maximum values, regular expressions, constraints on the length of strings, and constraints on the number of digits in decimal values. XSD 1.1 again adds assertions, the ability to specify an arbitrary constraint by means of an XPath 2.0 expression. Complex types describe

2254-622: The standard matures. A candidate recommendation is a version of a more mature standard than the WD. At this point, the group responsible for the standard is satisfied that the standard meets its goal. The purpose of the CR is to elicit aid from the development community on how implementable the standard is. The standard document may change further, but significant features are mostly decided at this point. The design of those features can still change due to feedback from implementors. A proposed recommendation

2303-668: The textual values that may appear in an element or attribute. This is one of the more significant ways in which XML Schema differs from DTDs. For example, an attribute might be constrained to hold only a valid date or a decimal number. XSD provides a set of 19 primitive data types ( anyURI , base64Binary , boolean , date , dateTime , decimal , double , duration , float , hexBinary , gDay , gMonth , gMonthDay , gYear , gYearMonth , NOTATION , QName , string , and time ). It allows new data types to be constructed from these primitives by three mechanisms: Twenty-five derived types are defined within

2352-545: The types usize and isize which are unsigned and signed integers that are the same bit width as a reference with the usize type being used for indices into arrays and indexable collection types. Rust also has: Built-in types are distinguished from others by having specific support in the compiler or runtime, to the extent that it would not be possible to simply define them in a header file or standard library module. Besides integers, floating-point numbers, and Booleans, other built-in types include: A character type

2401-469: The validation engine, or it can be referenced directly from the instance document using two special attributes, xsi:schemaLocation and xsi:noNamespaceSchemaLocation . (The latter mechanism requires the client invoking validation to trust the document sufficiently to know that it is being validated against the correct schema. "xsi" is the conventional prefix for the namespace " http://www.w3.org/2001/XMLSchema-instance ".) XML Schema Documents usually have

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