What is the difference between XML and XSD

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What is the difference between Extensible Markup Language  XML  and XML Schema  XSD

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XSD    XSD  XML Schema Definition   specifies how to formally describe the elements in an Extensible Markup Language  XML  document  Xml  XML was designed to describe data It is independent from software as well as hardware  It enhances the following things    -Data sharing    -Platform independent    -Increasing the availability of Data   Differences        XSD is based and written on XML  XSD defines elements and structures that can appear in the document  while XML does not  XSD ensures that the data is properly interpreted  while XML does not  An XSD document is validated as XML  but the opposite may not always be true  XSD is better at catching errors than XML         An XSD defines elements that can be used in the documents  relating to the actual data with which it is to be encoded  for eg  A date that is expressed as 1 12 2010 can either mean January 12 or December 1st  Declaring a date data type in an XSD document  ensures that it follows the format dictated by XSD

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Basically an XSD file defines how the XML file is going to look like  It s a Schema file which defines the structure of the XML file  So it specifies what the possible fields are and what size they are going to be   An XML file is an instance of XSD as it uses the rules defined in the XSD

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SIMPLE XML EXAMPLE    lt school gt     lt firstname gt John lt  firstname gt     lt lastname gt Smith lt  lastname gt   lt  school gt    XSD OF ABOVE XML Explained     lt xs element name  school  gt     lt xs complexType gt       lt xs sequence gt         lt xs element name  firstname  type  xs string   gt         lt xs element name  lastname  type  xs string   gt       lt  xs sequence gt     lt  xs complexType gt   lt  xs element gt    Here   xs element   Defines an element   xs sequence   Denotes child elements only appear in the order mentioned   xs complexType   Denotes it contains other elements   xs simpleType   Denotes they do not contain other elements   type  string  decimal  integer  boolean  date  time    In simple words  xsd is another way to represent and validate XML data with the specific type  With the help of extra attributes  we can perform multiple operations  Performing any task on xsd is simpler than xml

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XML versus XSD  XML defines the syntax of elements and attributes for structuring data in a well-formed document   XSD  aka XML Schema   like DTD before  powers the eXtensibility in XML by enabling the user to define the vocabulary and grammar of the elements and attributes in a valid XML document

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Take an example   lt root gt     lt parent gt        lt child one gt Y lt  child one gt        lt child two gt 12 lt  child two gt     lt  parent gt   lt  root gt    and design an xsd for that    lt xs schema attributeFormDefault  unqualified  elementFormDefault  qualified   xmlns xs  http   www w3 org 2001 XMLSchema  gt     lt xs element name  root  gt       lt xs complexType gt         lt xs sequence gt           lt xs element name  parent  gt             lt xs complexType gt               lt xs sequence gt                 lt xs element name  child one  type  xs string    gt                 lt xs element name  child two  type  xs int    gt               lt  xs sequence gt             lt  xs complexType gt           lt  xs element gt         lt  xs sequence gt       lt  xs complexType gt     lt  xs element gt   lt  xs schema gt    What isn t possible with XSD  would like to write it first as the list is very small 1  You can t validate a node attribute using the value of another node attribute  2  This is a restriction   An element defined in XSD file must be defined with only one datatype   in the above example  for  lt child two gt  appearing in another  lt parent gt  node  datatype cannot be defined other than int  3  You can t ignore the validation of elements and attributes  ie  if an element attribute appears in XML  it must be well-defined in the corresponding XSD  Though usage of   lt xsd any gt  allows it  but it has got its own rules  Abiding which leads to the validation error  I had tried for a similar approach  and certainly wasn t successful  here is the Q amp A  what are possible with XSD  1  You can test the proper hierarchy of the XML nodes   xsd defines which child should come under which parent  etc  abiding which will be counted as error  in above example  child two cannot be the immediate child of root  but it is the child of  parent  tag which is in-turn a child of  root  node  there is a hierarchy    2  You can define Data type of the values of the nodes   in above example child two cannot have any-other data than number  3  You can also define custom data types   example  for node  lt month gt   the possible data can be one of the 12 months   so you need to define all the 12 months in a new data type writing all the 12 month names as enumeration values    validation shows error if the input XML contains any-other value than these 12 values      4  You can put the restriction on the occurrence of the elements  using minOccurs and maxOccurs  the default values are 1 and 1      and many more

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XML has a much wider application than f ex  HTML  It doesn t have an intrinsic  or default  application   So  while you might not really care that web pages are also governed by what s allowed  from the author s side  you ll probably want to precisely define what an XML document may and may not contain   It s like designing a database   The thing about XML technologies is that they are textual in nature  With XSD  it means you have a data structure definition framework that can be  plugged in  to text processing tools like PHP  So not only can you manipulate the data itself  but also very easily change and document the structure  and even auto-generate front-ends   Viewed like this  XSD is the  glue  or  middleware  between data  XML  and data-processing tools

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Actually the XSD is XML itself  Its purpose is to validate the structure of another XML document  The XSD is not mandatory for any XML  but it assures that the XML could be used for some particular purposes  The XML is only containing data in suitable format and structure

[xml] What is the difference between XML and XSD?

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