XML (eXtensible Markup Language)

A markup language is an artificial language using a set of annotations to text that give instructions regarding the structure, the content or how it is to be displayed, that is to say, meta-information (information about information). Examples: Tex, SGML, HTML, XML, XHTML, SOAP.

SGML (Standard Generalized Markup Language, ISO since 1986) is a metalanguage in which one can define markup languages for documents. SGML is a descendant of IBM’s GML, developed in the 1960s by Charles Goldfarb, Edward Mosher and Raymond Lorie. Example: HTML

XML (eXtensible Markup Language) is a general-purpose specification for creating custom markup languages. It started as a simplified subset of the SGML (Standard Generalized Markup Language), and is designed to be relatively human-legible. In 1996 W3C decided to remodule SGML to make it more powerful and strict but much simpler to use/parse and recruited John Bosak from Sun as the project leader. Finally, in 1998 W3C presented XML as a fee-free open standard. Examples: XHTML, RSS, SVG, SOAP.

xml

DTD (XML Document Type Definition)(DEPRECADED) is an XML that defines the document structure and syntax (allowed tags, tags order/hierarchy/nesting). A DTD can be declared internally in your XML document, or as an external reference (file.dtd). Example persons.dtd:

<!ELEMENT persons (persona*)>  * = [0,n] (0 or more persons)
<!ELEMENT person (name,sex?)>  ? = [0,1] (sex is optional)
<!ELEMENT name (#PCDATA) >     requieres #PCDATA
<!ELEMENT sex (#PCDATA) >

Example person.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE persons SYSTEM "persons.dtd">
<persons>
  <person>
    <name>John Smith</name>
    <sex>male</sex>
  </person>
</persons>

Limitations: Do not manage local names (namespaces) and data types. Solution: XML Schema (XSD) (W3C)

DTDs –> XSDs (XML Shemas)

XS, XSD, XSDL (XML Schema Definition Language) (W3C 2001)

Solves DTD problems: namespaces and data types. Online tutorial. Example:

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="Person">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Name" type="xs:string" />
        <xs:element name="Sex">
          <xs:simpleType>
            <xs:restriction base="xs:string">
              <xs:enumeration value="Male" />
              <xs:enumeration value="Female" />
            </xs:restriction>
          </xs:simpleType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

XSL (eXtensible Stylesheet Language):

XSL consists of three parts:

XSLT – a language for transforming XML documents
XPath – a language for navigating in XML documents
XSL-FO – a language for formatting XML documents

XSLT (eXtensible Stylesheet Language Transformations)

XPath (XML Path Language)…navigate xml… estudiar TUTORIAL (1,2,3,4)

XSL-FO (XSL Formating) formating

XQuery as an extension of XPath: Although both XPath and XQuery perform some of the same functions, XPath provides simplicity and XQuery provides additional power and flexibility.

XQuery is the language for querying XML data
XQuery for XML is like SQL for databases
XQuery is built on XPath expressions
XQuery is supported by all the major database engines (IBM, Oracle, Microsoft, etc.)
XQuery is a W3C Recommendation

PARSERS

IMPORTANT: SAX vs DOM

SAX (Simple API for XML): Fast, sequential, top2bottom, 1time read. (Java)

DOM (Document Object Model): Slower, tree structure, forward and backward, random access, W3C. The XML DOM defines a standard way for accessing and manipulating XML documents. Knowing the XML DOM is a must for anyone working with XML. The DOM represents an XML document as a tree structure, with elements, attributes, and text as nodes:

DOM node tree

XML Utils:

Bash: libxml2 – XMLStarlet (XMLStarlet-basic-kit)(tutorial) – XMLLINT
C++: libxml2 (XML) – Xerces (DOM)
Apache COCOON project (Xerces,…)
Java: JAXP – native/Xerces (DOM)

IMPORTANT. VER http://www.tutorialized.com/view/tutorial/Improve-performance-of-XML-apps-using-Xerces-C/35630

http://www.ibm.com/developerworks/xml/library/x-xercc/?ca=dgr-xw766x-xercc

http://www.ibm.com/developerworks/xml/library/x-xercc2/

BNF (Backus-Naur Form): BNF is a formal meta-syntax used to express context-free Grammars CFG. BNF is one of the most commonly used meta-syntactic notations for specifying the syntax of programming languages, command sets, etc. However, pure BNF is rather limited, so the two variations EBNF and ABNF have become more popular.

TIMEML…