What is the purpose of XSD files

Question

Since we can query on the XML file from C    NET   why do we need an XSD file  I know it is metadata file of particular XML file   We can specify the relationships in XSD  but what is its functioning then    XML   lt  xml version  1 0  encoding  utf-8    gt   lt Root gt     lt Customers gt       lt Customer CustomerID  GREAL  gt         lt CompanyName gt Great Lakes Food Market lt  CompanyName gt         lt ContactName gt Howard Snyder lt  ContactName gt         lt ContactTitle gt Marketing Manager lt  ContactTitle gt         lt Phone gt  503  555-7555 lt  Phone gt         lt FullAddress gt           lt Address gt 2732 Baker Blvd  lt  Address gt           lt City gt Eugene lt  City gt           lt Region gt OR lt  Region gt           lt PostalCode gt 97403 lt  PostalCode gt           lt Country gt USA lt  Country gt         lt  FullAddress gt       lt  Customer gt     lt  Customers gt     lt Orders gt       lt Order gt         lt CustomerID gt GREAL lt  CustomerID gt         lt EmployeeID gt 6 lt  EmployeeID gt         lt OrderDate gt 1997-05-06T00 00 00 lt  OrderDate gt         lt RequiredDate gt 1997-05-20T00 00 00 lt  RequiredDate gt         lt ShipInfo ShippedDate  1997-05-09T00 00 00  gt           lt ShipVia gt 2 lt  ShipVia gt           lt Freight gt 3 35 lt  Freight gt           lt ShipName gt Great Lakes Food Market lt  ShipName gt           lt ShipAddress gt 2732 Baker Blvd  lt  ShipAddress gt           lt ShipCity gt Eugene lt  ShipCity gt           lt ShipRegion gt OR lt  ShipRegion gt           lt ShipPostalCode gt 97403 lt  ShipPostalCode gt           lt ShipCountry gt USA lt  ShipCountry gt         lt  ShipInfo gt       lt  Order gt       lt Order gt         lt CustomerID gt GREAL lt  CustomerID gt         lt EmployeeID gt 8 lt  EmployeeID gt         lt OrderDate gt 1997-07-04T00 00 00 lt  OrderDate gt         lt RequiredDate gt 1997-08-01T00 00 00 lt  RequiredDate gt         lt ShipInfo ShippedDate  1997-07-14T00 00 00  gt           lt ShipVia gt 2 lt  ShipVia gt           lt Freight gt 4 42 lt  Freight gt           lt ShipName gt Great Lakes Food Market lt  ShipName gt           lt ShipAddress gt 2732 Baker Blvd  lt  ShipAddress gt           lt ShipCity gt Eugene lt  ShipCity gt           lt ShipRegion gt OR lt  ShipRegion gt           lt ShipPostalCode gt 97403 lt  ShipPostalCode gt           lt ShipCountry gt USA lt  ShipCountry gt         lt  ShipInfo gt       lt  Order gt     lt  Orders gt   lt  Root gt    I want to get data from the Order elements according to a provided CustomerID   Also  What is the purpose of giving the relationships in XSD

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Before understanding the XSD XML Schema Definition  let me explain        What is schema    for example  emailID  peter gmail     You can identify the above emailID is not valid because there is no     com or  net or  org   We know the email schema it looks like peter gmail com      Conclusion  Schema does not validate the data  It does the validation of structure     XSD is actually one of the implementation of XML Schema  others we have relaxng  We use XSD to validate XML data

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An  xsd file is called an XML schema  Via an XML schema  we may require a certain structure in a given XML - which elements in which order  how many times  with which attributes  how they are nested  etc  If we have a schema for our XML input  we can verify that it contains the data we need it to contain  and nothing else  with a few lines invoking a schema validator

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An XSD is a formal contract that specifies how an XML document can be formed  It is often used to validate an XML document  or to generate code from

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Also questions is  What is the purpose   of giving the relationships in xsd    Suppose you want to generate some XML for an external party s tool  or similar - how would you know what structure it is allowed to follow to be used correctly for their tool  you write to a schema  Likewise if you want other people to use your tool  you would write a schema for them to follow   It may also be useful for validating your own XML

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XSDs constrain the vocabulary and structure of XML documents    Without an XSD  an XML document need only follow the rules for being well-formed as given in the W3C XML Recommendation  With an XSD  an XML document must adhere to additional constraints placed upon the names and values of its elements and attributes in order to be considered valid against the XSD per the W3C XML Schema Recommendation    XML is all about agreement  and XSDs provide the means for structuring and communicating the agreement beyond the basic definition of XML itself

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The xsd file is the schema of the xml file - it defines which elements may occur and their restrictions  like amount  order  boundaries  relationships

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Without XML Schema  XSD file  an XML file is a relatively free set of elements and attributes  The XSD file defines which elements and attributes are permitted and in which order   In general XML is a metalanguage  XSD files define specific languages within that metalanguage  For example  if your XSD file contains the definition of XHTML 1 0  then your XML file is required to fit XHTML 1 0 rather than some other format

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XSD files are used to validate that XML files conform to a certain format   In that respect they are similar to DTDs that existed before them   The main difference between XSD and DTD is that XSD is written in XML and is considered easier to read and understand

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An XSD file is an XML Schema Definition and it is used to provide a standard method of checking that a given XML document conforms to what you expect

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You mention C  in your question so it may help to think of as XSD as serving a similar role to a C  interface    It defines what the XML should  look like  in a similar way that an interface defines what a class should implement

[xml] What is the purpose of XSD files?

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