Pengenalan XML

Extensible markup language

XML (Extensible Markup Language) adalah bahasa markup untuk keperluan umum yang disarankan oleh W3C untuk membuat dokumen markup keperluan pertukaran data antar sistem yang beraneka ragam. XML merupakan kelanjutan dari HTML (HyperText Markup Language) yang merupakan bahasa standar untuk melacak Internet.

Mengenal XML

XML didesain untuk mempu menyimpan data secara ringkas dan mudah diatur. Kata kunci utama XML adalah data (jamak dari datum) yang jika diolah bisa memberikan informasi

XML menyediakan suatu cara terstandarisasi namun bisa dimodifikasi untuk menggambarkan isi dari dokumen. Dengan sendirinya, XML dapat digunakan untuk menggambarkan sembarang view database, tetapi dengan suatu cara yang standar.

Tipe XML

XML memiliki tiga tipe file :

XML, merupakan standar format dari struktur berkas (file).

XSL, merupakan standar untuk memodifikasi data yang diimpor atau diekspor.

XSD, merupakan standar yang mendefinisikan struktur database dalam XML.

Keunggulan XML

Keunggulan XML bisa diringkas sebagai berikut :

Pintar (Intelligence). XML dapat menangani berbagai tingkat (level) kompleksitas.

Dapat beradaptasi. Dapat mengadaptasi untuk membuat bahasa sendiri. Seperti Microsoft membuaat bahasa MSXML atau Macromedia mengembangkan MXML.

Mudah pemeliharaannya.

Sederhana. XML lebih sederhana.

Mudah dipindah-pindahkan (Portability). XML mempunyai kemudahan perpindahan (portabilitas) yang lebih bagus.

Contoh dokumen XML sederhana

version="1.0" encoding="UTF-8"?> nama="roti" waktu_persiapan="5 menit" waktu_masak="3 jam"> >Roti tawar> jumlah="3" satuan="cangkir">Tepung> jumlah="0,25" satuan="ons">Ragi> jumlah="1,5" satuan="cangkir">Air hangat> jumlah="1" satuan="sendok teh">Garam> > >Campur semua bahan dan uleni adonan sampai merata.> >Tutup dengan kain lembab dan biarkan selama satu jam di ruangan yang hangat.> >Ulangi lagi, letakkan di loyang dan panggang di oven.> >Keluarkan, hidangkan> > >

Aturan Syntax XML

The syntax rules of XML are very simple and logical. The rules are easy to learn, and easy to use.

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All XML Elements Must Have a Closing Tag

In HTML, elements do not have to have a closing tag:

This is a paragraph This is another paragraph

In XML, it is illegal to omit the closing tag. All elements must have a closing tag:

This is a paragraph This is another paragraph

Note: You might have noticed from the previous example that the XML declaration did not have a closing tag. This is not an error. The declaration is not a part of the XML document itself, and it has no closing tag.

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XML Tags are Case Sensitive

XML tags are case sensitive. The tag is different from the tag .

Opening and closing tags must be written with the same case:

This is incorrect This is correct

Note: "Opening and closing tags" are often referred to as "Start and end tags". Use whatever you prefer. It is exactly the same thing.

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XML Elements Must be Properly Nested

In HTML, you might see improperly nested elements:

This text is bold and italic

In XML, all elements must be properly nested within each other:

This text is bold and italic

In the example above, "Properly nested" simply means that since the element is opened inside the element, it must be closed inside the element.

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XML Documents Must Have a Root Element

XML documents must contain one element that is the parent of all other elements. This element is called the root element.

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XML Attribute Values Must be Quoted

XML elements can have attributes in name/value pairs just like in HTML.

In XML, the attribute values must always be quoted.

Study the two XML documents below. The first one is incorrect, the second is correct:

Tove Jani

Tove Jani

The error in the first document is that the date attribute in the note element is not quoted.

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Entity References

Some characters have a special meaning in XML.

If you place a character like "<" inside an XML element, it will generate an error because the parser interprets it as the start of a new element.

This will generate an XML error:

if salary < 1000 then

To avoid this error, replace the "<" character with an entity reference:

if salary < 1000 then

There are 5 predefined entity references in XML:

<	<	less than
>	>	greater than
&	&	ampersand
'	'	apostrophe
"	"	quotation mark

Note: Only the characters "<" and "&" are strictly illegal in XML. The greater than character is legal, but it is a good habit to replace it.

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Comments in XML

The syntax for writing comments in XML is similar to that of HTML.

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White-space is Preserved in XML

HTML truncates multiple white-space characters to one single white-space:

HTML:	Hello Tove
Output:	Hello Tove

With XML, the white-space in a document is not truncated.

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XML Stores New Line as LF

In Windows applications, a new line is normally stored as a pair of characters: carriage return (CR) and line feed (LF). In Unix applications, a new line is normally stored as an LF character. Macintosh applications also use an LF to store a new line.

XML stores a new line as LF.

What is an XML Element?

An XML element is everything from (including) the element's start tag to (including) the element's end tag.

An element can contain:

other elements

text

attributes

or a mix of all of the above...

J K. Rowling 2005 29.99 Erik T. Ray 2003 39.95

In the example above, and have element contents, because they contain other elements. also has an attribute (category="CHILDREN").