Xml is an Extensible Markup Language which defines a set of
rules and encoding documents. It is the SGML application profile. Xml is set up
in 1980s for the dynamic information display when use of internet rise. SGML
offered solutions for some problems which the World web likes to face. XML is
created by eleven member groups and its design work was completed by Michael Sprerbery-McQueen
on December 4, 1997, which contributing the empty element <empty> syntax
and name XML. Other names consider including “MAGMA”(Minimal Architecture for Generalized Markup Application), “SLIM”(Structured Language or Internet Markup), “MGML”(Minimal Generalized Markup Language) and its
editors were originally Tim Bray and Michael Sprerbery-McQueen. The first XML
draft was published in August and November 1996 and XML 1.0 recommended on
February 10, 1998 which became a W3C
Xml separate logical and physical based. It is the TEI (Text
Encoding Initiative), define as profile of SGML and Html which synchronous
resource, character sets resource encoding.
There are two versions available of XML that is the XML 1.0
which was initially defined in 1998 and the XML 1.1 which was initially
published on February 4, 2004. Both version are different from each other the
XML 1.0 version include elements, attribute and unique identifiers and the 1.0
version include Unicode standard from 2.0 to 3.2. XML is used to create encode
documents and serialize data, purpose to facilitate sharing of structured data.
Advantages and Disadvantages
Advantages
- Its encoding are readable with referring any book or file as because it is based on human-encoding. Data specified element enclosed by tags and unique to parent element can specified. Like:-
<customer action=”00012” current balance=”2.0”>
<name>Smith</name>
<name>Paul</name>
</customer>
</file>
- Xml can be store in binary data which must be converted into text usually done with an algorithm. Algorithm used to convert data to text. Wikipedia is such an example. A binary character also separated by numeric characters like &#x.
- It can store data or any document that represent a tree structure.
- XML can easily display o n browsers, browser usually display XML file as a tree/collapsible list.
Disadvantages
- It can’t be originally defined as database storage platform because designed to accommodate exchange of data between nodes. Like
- Binary formatted file account number: 00100001234 or 11 bytes.
- XML format file account number: <acctno>00100001234</acctno> or 28 bytes.
- Additional program display encoded image data represented in XML, which appears as stream of unintelligible character data.
- Used to transmit and store document for visual display as storage is not its primary or original purpose.
It has three methods to parse XML files which include
program APIs and the search engine.
Two interesting Markup Language base on XML
- InkML (Ink Markup Language)
The current InkML specification defines a set of primitive
elements sufficient for all basic ink application. It contain within a single
<ink> element. Fundamental element is
<trace>
For example :-
- RecipeML (Recipe Markup Language)
A format for representing recipes on computer. It is written
in the increasingly popular Extensible Markup Language-XML. For electronic representation of recipes
whether online or in a software or in any other soft-form, RecipeML can be
used.
For Example:-
<recipe>
<head>
<title> Smores </title>
</head>
<ingredients>
<ing>
<amt><qty> 2 </qty></amt>
<item> Graham crackers </item>
</ing>
</ingredient>
<directions>
<step> place two marshmallows on a graham
cracker</step>
<step> place chocolates square on each
marshmallows</step>
</directions>
</recipe>
XML Structure
A style sheet presentation through CSS or XSL.
A grammar structure through DTD.
Semantics of data through XML file.
Structure of XML-file/document
- Logical Structure – basically tells about what all elements are to be included in the document, the order of elements, contains mainly Prolog and Data Instance
- Physical Structure – basically tells about an entity is a storage unit, Parsed Entity is processed by XML-processed such as XML-parser, Unparsed Entity contains related information and is not processed by XML-parser.
Logical Structure of XML Document
- Data Prolog, and
- The Data Instance
The Prolog
- An XML declaration – XML declaration that identifies XML version, Encoding, stand-alone or not.
- Processing Instructions (PIs) – instructions that pass information to the application/
- A document type declaration (DTD) – consists of Markup code that includes the grammar rules for the particular class of the document, grammar rules are called Document Type Definition (DTD).
- DTD defines with !DOCTYPE declaration
- (Comments – are not processed by XML-parses to add notes about document structure and to break a document into sections
- White Space – refers to a space, tabs, carriage-returns and blank lines, ignore additional white space.
Data Instance – consists of one or more elements.
- Root/Document Element – elements are means to define individual data items. An element begins with a start tag and and ends with a end tag.
- The parent element of all other elements in data instance is known as root element or document element.
- Elements Types – data instance is made up of elements contained inside one parent element. Elements that are nested inside the root element belong to one of the three categories – Start tag, End tags and declared empty element tag
- Child Elements – other tags nested inside it
- Attributes – property setting of the element defined through name-value pairs along with the start tag.
XML Document Categories
- Well-designed Documents – that obeys XML grammar rules.
- Valid Document – well-formed as well as confirms to the specifications of DTD. DTD is a set of rules that defines what tags appear in an XML document, so that viewers of an XML document know what all tags mean, also describe the structure of a document.
- Cascading Style Sheet (CSS) – collection of formatting rules that control the appearance of content in a web page. A Stylesheet is made up of style rules that tell a browser how a present a document.
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