figis’ml hands-on training - © fao/figis 2001 1 an introduction to xml objectives : –what is...

FIGIS’ML Hands-on training - © FAO/FIGIS 2001 1

An introduction to XML

• Objectives :– what is XML?– XML and HTML– XML documents

• structure• well-formedness

– Validation of XML documents :• the DTDs• creation of a DTD• the schemas

– creating XML documents



• What is XML? :– XML stands for eXtensible Markup Language

• XML is similar to HTML but– HTML deals with presentation– XML deals with content and structure

• XML is extensible : you can create your own tags

– XML is an open standard managed by the World Wide Web Consortium (W3C)

• http://www.w3c.org

– XML is text-based



• What is XML? : an example

<?xml version="1.0" encoding="iso-8859-1"?><ORDER orderref="120136">

<ITEM type="CD" quantity="1"><AVAILABLE STATUS=“yes” TIME=“2days”/><TITLE>Groovy beats</TITLE><AUTHOR>Howie C.</AUTHOR><EDITOR>Average Records</EDITOR>

</ITEM><ITEM type="book" quantity="2">

<AVAILABLE STATUS=“yes” TIME=“1week”/> <TITLE>Piano for Dummies - vol1</TITLE><AUTHOR> K. Board</AUTHOR><EDITOR>Dubious & P. Ano</EDITOR>

</ITEM></ORDER>



• XML and HTML– HTML :

• pros : widely used, simple to use;• cons : mixes data and formatting, non-extensible

– XML :• handles only the content - formatting is done by

stylesheets• the tags are defined by the authors• tags definition and structure is handled by dictionnaries

(DTD)



• XML and HTML : examples– HTML

– XML<?xml version="1.0" encoding="iso-8859-1"?><ORDER orderref="120136">

<ITEM type="CD" quantity="1"><AVAILABLE STATUS=“yes” TIME=“2days”/><TITLE>Groovy beats</TITLE><AUTHOR>Howie C.</AUTHOR><EDITOR>Average Records</EDITOR>

</ITEM></ORDER>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><body>

<table width="200" border="1"><tr><td><B>Groovy beats</B></td></tr><tr><td>Howie C.</td></tr><tr><td>Average Records</td></tr>

</table></body></html>



• an XML document


<ITEM type="CD" quantity="1"><AVAILABLE status="yes" time="2days"/><TITLE>Groovy beats</TITLE><AUTHOR>Howie C.</AUTHOR><EDITOR>Average Records</EDITOR>


<AVAILABLE status="yes" time="1week"/><TITLE>Piano for Dummies - vol1</TITLE><AUTHOR>K. Board</AUTHOR><EDITOR>Dubious & P. Ano</EDITOR>

</ITEM></ORDER>

declaration

element

entity

attribute

root



• an XML document– Elements

• they define the document’s content• they can contain other elements or text• they can be empty

– Attributes• add information about one element• one attribute can only appear once in one element• attributes can only contain text

– Entities• can be used as “shortcuts”• are similar to variables



• an XML document– Declaration

• always the first line of an XML document• can be omitted (not recommended)• always like : <?xml version="1.0”>• can contain language-related info :

<?xml version="1.0" encoding="iso-8859-1"?>

– Root (element)• mandatory• always unique



• Creating well-formed XML documents– well-formed means that the document

respects the XML rules– the main rules are :

• there must be a root• there must be at least one element inside the root• all elements must be properly imbricated and closed• elements, attributes and entities are case-sensitive• attribute values have to be quoted



• Valid XML documents– an XML document is valid when :

• it follows the structure that has been defined• all the elements respect the defined rules

– valid elements– valid attributes– optional and mandatory elements/attributes

– the validation rules are defined in a “dictionnary” :

• a Document Type Definition (DTD)• a schema (still a proposal)



• Valid XML documents– well-formed doesn’t imply valid

• well-formed means syntaxically correct• valid is similar to grammatically correct

– but a valid document is always well-formed



• Valid XML documents : DTD– Creating a DTD : sample XML




<AVAILABLE status="yes" time="1week"/><TITLE>Piano for Dummies - vol1</TITLE><AUTHOR>K. Board</AUTHOR><EDITOR>Dubious & P. Ano </EDITOR>

</ITEM></ORDER>



• Valid XML documents : DTD– Creating a DTD :

• insert the declaration<?xml version="1.0" encoding="iso-8859-1"?>

• identify the root elementORDER

• identify its direct childrenITEM with TYPE and Quantity as attributes

• define children grouping and repetitionany number of ITEM elements

• repeat these steps for each level of elementsITEM contains one mandatory occurrence of AVAILABLE, TITLE, AUTHOR and

EDITOR



• Valid XML documents : DTD– Creating a DTD :

• define root element :<!ELEMENT ORDER

• define its direct children and their order/number:<!ELEMENT ORDER (ITEM+)>

• repeat those steps for each element :<!ELEMENT ITEM (AVAILABLE,TITLE,AUTHOR,EDITOR)>

• define the attributes of each element :<!ATTLIST ORDER orderref CDATA #REQUIRED>



• Valid XML documents : DTD– Creating a DTD : grouping an repeating

elements• specifiying the number of elements :

– 0 or 1 : <!ELEMENT ORDER(ITEM?)>– 1 or more : <!ELEMENT ORDER(ITEM+)>– 0 or more : <!ELEMENT ORDER(ITEM*)>– 1 exactly : <!ELEMENT ORDER(ITEM)>

• specifying the order of elements :– any order : <!ELEMENT ITEM(AUTHOR | TITLE)>– specified order : <!ELEMENT ITEM(TITLE,AUTHOR)>

• and any combination of those :<!ELEMENT HISTORY(ORDER*,DATE?,(CUSTOMER+ | COMPANY+))>



• Valid XML documents : DTD– Creating a DTD : elements content

• elements can be empty :– example : <AVAILABLE status="yes" time="2days"/>– they should be declared using EMPTY :

<!ELEMENT AVAILABLE EMPTY>

• elements can contain other elements :<ORDER orderref="120136">

<ITEM type="CD" quantity="1">...

</ORDER>

• elements can contain text :– example : <TITLE>Groovy beats</TITLE>– they should be declared using (#PCDATA):

<!ELEMENT TITLE (#PCDATA)>



• Valid XML documents : DTD– Creating a DTD : adding attributes

• using ATTLIST :<!ATTLIST ITEM

TYPE (CD | book) “CD”

QUANTITY CDATA #REQUIRED

>

• this defines :– two attributes of the element ITEM– gives the list of possible TYPE values (“CD”/“book”)– defines “CD” as the default value for TYPE– defines QUANTITY as a mandatory attribute

• there are three attribute types :– #REQUIRED : a value is mandatory– #IMPLIED : a value is optional– #FIXED : the attribute always has the same value



• Valid XML documents : DTD– Creating a DTD : example




<AVAILABLE status="yes" time="1week"/><TITLE>Piano for Dummies - vol1</TITLE><AUTHOR>K. Board</AUTHOR><EDITOR>Dubious & P. Ano </EDITOR>

</ITEM></ORDER>



• Valid XML documents : DTD– Creating a DTD : example

• hands-on : creating a DTD with XMLSpy• this is the DTD defined for the sample XMl document :

<?xml version="1.0" encoding="iso-8859-1"?>

<!ELEMENT ORDER (ITEM+)>

<!ATTLIST ORDER

orderref CDATA #REQUIRED

>

<!ELEMENT ITEM (AVAILABLE, TITLE, AUTHOR, EDITOR)>

<!ATTLIST ITEM

TYPE (CD | book) "CD"

QUANTITY CDATA #REQUIRED

>

<!ELEMENT AVAILABLE EMPTY>

<!ATTLIST AVAILABLE

TIME (2days | 1week | normal) #IMPLIED

STATUS (YES | NO) #REQUIRED

>

<!ELEMENT TITLE (#PCDATA)>

<!ELEMENT AUTHOR (#PCDATA)>

<!ELEMENT EDITOR (#PCDATA)>



• Valid XML documents : schemas– schemas are still a proposal– schemas are written in XML

• they don’t require learning a new language• they can be handled and transformed as normal XML

documents

– schemas can contain more complex rules that DTDs

• conditions• tests• ...



• creating XML documents– XML is pure text– XML documents can be created manually– XML editing softwares make the task easier

• check for well-formedness and validity• provide a graphical user interface

– Various solutions exist :• XMLSpy by Altova (Windows)• Xmetal by SoftQuad(Windows)• Morphon XML Editor Suite by Morphon (MacOS)• ElfData XML Editor by ElfData (MacOS)



• Creating XML documents :– hands-on : creating a document with XMLSpy

• example of an order form :– 1 order : reference 120136– two items in the order :

» 1 CD, “Groovy beats” by Howie C., ed. “Average Records”, available with 2-days delivery

» 2 copies of the book “Piano for dummies - vol1” by K. Board, published by “Dubious & P. Ano”, available with 1-week delivery



• Creating XML documents :– hands-on : creating a document with XMLSpy




<AVAILABLE status="yes" time="1week"/><TITLE>Piano for Dummies - vol1</TITLE><AUTHOR>K. Board</AUTHOR><EDITOR>Dubious & P. Ano</EDITOR>

</ITEM></ORDER>



• using XML documents– exchanging data between systems

• from a DB to another DB• data manipulation by softwares

– submitting data to a system• automatically (software)• manually (creation of content)

– presenting data to the user• web pages• data export in any format (text, pdf, etc.)

figis’ml hands-on training - © fao/figis 2001 1 an introduction to xml objectives : –what is...

Documents