What is the purpose of XSD files ?

Question

though we can query on the xml file from c# (.net). why need of .xsd file ? I know it is metadata file of particular xml file. we can specify the relationships in xsd. but what its functioning then ?

Sure: See, I have the xml:

<?xml version="1.0" encoding="utf-8" ?>
<Root>
  Customers->
    ->Customer 
        ->CustomerID="GREAL">->
      <CompanyName>Great Lakes Food Market</CompanyName>
      <ContactName>Howard Snyder</ContactName>
      <ContactTitle>Marketing Manager</ContactTitle>
      <Phone>(503) 555-7555</Phone>
      <FullAddress>
        <Address>2732 Baker Blvd.</Address>
        <City>Eugene</City>
        <Region>OR</Region>
        <PostalCode>97403</PostalCode>
        <Country>USA</Country>
      </FullAddress>
    <-</Customer>

 <- </Customers>



<Orders>
    <Order>
      <CustomerID>GREAL</CustomerID>
      <EmployeeID>6</EmployeeID>
      <OrderDate>1997-05-06T00:00:00</OrderDate>
      <RequiredDate>1997-05-20T00:00:00</RequiredDate>
      <ShipInfo ShippedDate="1997-05-09T00:00:00">
        <ShipVia>2</ShipVia>
        <Freight>3.35</Freight>
        <ShipName>Great Lakes Food Market</ShipName>
        <ShipAddress>2732 Baker Blvd.</ShipAddress>
        <ShipCity>Eugene</ShipCity>
        <ShipRegion>OR</ShipRegion>
        <ShipPostalCode>97403</ShipPostalCode>
        <ShipCountry>USA</ShipCountry>
      </ShipInfo>
    </Order>


    <Order>
      <CustomerID>GREAL</CustomerID>
      <EmployeeID>8</EmployeeID>
      <OrderDate>1997-07-04T00:00:00</OrderDate>
      <RequiredDate>1997-08-01T00:00:00</RequiredDate>
      <ShipInfo ShippedDate="1997-07-14T00:00:00">
        <ShipVia>2</ShipVia>
        <Freight>4.42</Freight>
        <ShipName>Great Lakes Food Market</ShipName>
        <ShipAddress>2732 Baker Blvd.</ShipAddress>
        <ShipCity>Eugene</ShipCity>
        <ShipRegion>OR</ShipRegion>
        <ShipPostalCode>97403</ShipPostalCode>
        <ShipCountry>USA</ShipCountry>
      </ShipInfo>
    </Order>

  </Orders>
</Root>

I want to get data from the ORDERS elements according to provided CustomeId.

Also questions is: What is the purpose of giving the relationships in xsd.

Answer 1

XSD files are used to validate XML - that is conforms 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.

Answer 2

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

Answer 3

Read this post and you'll get the idea.

Answer 4

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.

Answer 5

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.

Answer 6

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.

Answer 7

Without XML Schema (XSD file) a XML file is a relatively free set of elements and attributes. XSD file define which elements and attributes are permitted and in which order.

In general XML is a metalanguage. XSD define the language which you choosed. For example, you can use XSD which define XHTML 1.0, then your XML file permitted be only XHTML 1.0 and nothing more.

Answer 8

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.

Answer 9

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.