Getting started with Xsd

Let's take a look at the simple xsd below:

<? Xml version = "1.0" encoding = "UTF-8"?>

<Xs: schema xmlns: xs = "http://www.w3.org/2001/XMLSchema" elementFormDefault = "qualified"

AttributeFormDefault = "unqualified">

<Xs: element name = "ddd">

<Xs: annotation>

<Xs: documentation> Comment describing your root

Element </xs: documentation>

</Xs: annotation>

<Xs: complexType>

<Xs: sequence>

<Xs: element name = "bbb">

<Xs: complexType>

<Xs: choice>

<Xs: element name = "t"/>

</Xs: choice>

</Xs: complexType>

</Xs: element>

<Xs: group ref = "eg" minOccurs = "0"/>

<Xs: element name = "eee" minOccurs = "0"/>

</Xs: sequence>

</Xs: complexType>

</Xs: element>

<Xs: group name = "eg">

<Xs: choice>

<Xs: element name = "a"/>

<Xs: element name = "B" minOccurs = "0"/>

<Xs: element name = "c"/>

</Xs: choice>

</Xs: group>

</Xs: schema>

Below is an xml format that complies with this xsd:

<? Xml version = "1.0" encoding = "UTF-8"?>

<! -- Sample XML file generated by XMLSpy v2005 rel. 3 U (http://www.altova.com) -->

<Ddd xmlns: xsi = "http://www.w3.org/2001/XMLSchema-instance"

Xsi: noNamespaceSchemaLocation = "D: \ WordML \ testchoice. xsd">

<Bbb>

<T> </t>

</Bbb>

<A> </a>

<Eee> </eee>

</Ddd>

Xsd analysis:

1. xsd contains an element and a group

2. ddd is a complex type that contains a sequence. The default value of minocc and maxocc is 1, this requires that each sub-element of sequence be presented only once (but this does not mean that bbb, eg, and eee in ddd can appear only once, they can appear 0 or multiple times, this depends on the definition of these sub-levels, but the validators only know that "the sub-elements of sequence must be presented once, not many ")

3. The child element of sequence. The first bbb is also of the CT type, and contains the choice with the same default value as 1, therefore, ddd must contain a structure similar to "<bbb> <t> </bbb> ".

4. The second sub-level is group, and the minocc of group is 0. This determines that the eg group can be omitted. This also indicates that the xml document that complies with this xsd changes from this point on, and there may be different xml. (Then we can see that element B can be 0 times. This also means that even if the minocc of the eg group is not equal to 0, the eg group can be invisible .)

5. Finally, the eee element, minocc = 0, which also indicates that eee can be omitted. (Similarly, if you change the value of maxocc to greater than 1, ddd can contain multiple eee instances)

It can be seen that the simplest xml that conforms to the xsd architecture only needs to contain bbb and its child elements once.

The validator takes a step by step. It only requires that the current object meet the xsd and does not predict the sublevel.

In this way, we can write xml that meets the requirements according to xsd.