schema

SCHEMA OVERVIEW

e-logistics2009

Eduard Rodés GubernPort de Barcelona

Purpose of XML Schemas Specify:

the structure of instance documents “this element contains these elements, which contains these other

elements, etc" the datatype of each element/attribute

"this element shall hold an integer with the range 0 to 12,000" (DTDs don't do too well with specifying datatypes like this)

XML Schema is an XML-based language used to create XML-based languages and data models. An XML schema defines element and attribute names for a class of XML documents. The schema also specifies the structure that those documents must adhere to and the type of content that each element can hold.

XML documents that attempt to adhere to an XML schema are said to be instances of that schema. If they correctly adhere to the schema, then they are valid instances.

A First Look

An XML schema describes the structure of an XML instance document by defining what each element must or may contain. An element is limited by its type.

what each element contains1. Elements can be of simple type or complex type.

2. Simple type elements can only contain text. They can not have child elements or attributes.

3. All the built-in types are simple types (e.g, xs:string).

4. Schema authors can derive simple types by restricting another simple type. For example, an email type could be derived by limiting a string to a specific pattern.

5. Simple types can be atomic (e.g, strings and integers) or non-atomic (e.g, lists).

6. Complex-type elements can contain child elements and attributes as well as text.

7. By default, complex-type elements have complex content, meaning that they have child elements.

8. Complex-type elements can be limited to having simple content, meaning they only contain text. They are different from simple type elements in that they have attributes.

9. Complex types can be limited to having no content, meaning they are empty, but they have may have attributes.

10. Complex types may have mixed content - a combination of text and child elements.

Schema – friend.xsd<?xml version="1.0" encoding="UTF-8"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema“ targetNamespace="http://www.galactinav.com"

xmlns="http://www.galactinav.com" elementFormDefault="qualified"><xsd:element name="friend">

<xsd:complexType><xsd:sequence>

<xsd:element ref="name" minOccurs="1" maxOccurs="1"/><xsd:element ref="address" minOccurs="1" maxOccurs="unbounded"/>

</xsd:sequence></xsd:complexType>

</xsd:element><xsd:element name="address">


<xsd:element ref="street" minOccurs="1" maxOccurs="1"/><xsd:element ref="city" minOccurs="1" maxOccurs="1"/><xsd:element ref="country" minOccurs="1" maxOccurs="1"/><xsd:element ref="zip" minOccurs="1" maxOccurs="1"/>


</xsd:element><xsd:element name="name" type="xsd:string"/><xsd:element name="street" type="xsd:string"/><xsd:element name="city" type="xsd:string"/><xsd:element name="country" type="xsd:string"/><xsd:element name="zip" type="xsd:string"/></xsd:schema>

<!ELEMENT friend (name, address+)><!ELEMENT name (#PCDATA)><!ELEMENT address (street, city, country, zip)><!ELEMENT street (#PCDATA)><!ELEMENT city (#PCDATA)><!ELEMENT country (#PCDATA)><!ELEMENT zip (#PCDATA)>

ATTLISTELEMENT

ID

#PCDATA

NMTOKEN

ENTITY

CDATA

friend

namezip

address

country

citystreet

This is the vocabulary that DTDs provide to define yournew vocabulary

(Source:Roger L. Costello)

elementcomplexType

schema

sequence

http://www.w3.org/2001/XMLSchema

string

integer

boolean

This is the vocabulary that XML Schemas provide to define yournew vocabulary

One difference between XML Schemas and DTDs is that the XML Schema vocabularyis associated with a name (namespace). Likewise, the new vocabulary that you define must be associated with a name (namespace). With DTDs neither set ofvocabulary is associated with a name (namespace) [because DTDs pre-dated namespaces].

friend

namezip

address

country

citystreet

http://www.galactinav.com (targetNamespace)


XML instance document<?xml version="1.0" encoding="UTF-8"?><friend xmlns="http://www.galactinav.com"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.galactinav.com friend.xsd">

<name>El Soussy</name><address>

<street>Palestinian Gardens</street><city>Alexandria</city><country>EG</country><zip>90210</zip>

</address></friend> If you want to validate the files

http://tools.decisionsoft.com/schemaValidate/

Or download xmlspy www.altova.com

Referencing a schema in an XML instance document

BookStore.xml BookStore.xsd

targetNamespace="http://www.books.org"schemaLocation="http://www.books.org BookStore.xsd"

- defines elements in namespace http://www.books.org

- uses elements from namespace http://www.books.org

A schema defines a new vocabulary. Instance documents use that new vocabulary.(Source:Roger L. Costello)

Note multiple levels of checking

BookStore.xml BookStore.xsd XMLSchema.xsd(schema-for-schemas)

Validate that the xml documentconforms to the rules describedin BookStore.xsd

Validate that BookStore.xsd is a validschema document, i.e., it conformsto the rules described in theschema-for-schemas


Default Value for minOccurs and maxOccurs The default value for minOccurs is "1" The default value for maxOccurs is "1"

<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>

<xsd:element ref="Title"/>

Equivalent!


<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.galactinav.com" xmlns="http://www.galactinav.org" elementFormDefault="qualified"> <xsd:element name=“addressbook"> <xsd:complexType> <xsd:sequence> <xsd:element name=“friend" maxOccurs="unbounded"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="friend“>


<xsd:element name=“name”/><xsd:element name=“address" type=“addressdata” maxOccurs="unbounded"/>


</xsd:element><xsd:complexType name=“addressdata”>

<xsd:sequence><xsd:element name="street" type=“string”/><xsd:element name="city" type=“string”/><xsd:element name="country" type=“string”/><xsd:element name="zip" type=“string”/>


</xsd:schema>

Named type

The advantage ofsplitting out friend'selement declarationsand wrapping themin a named type isthat now this typecan be reused byother elements.

Named Types

Built-in datatypes

(Source:W3C Recomendation)

Built-in datatypesPrimitive

Note: 'T' is the date/time separator INF = infinity NAN = not-a-number

string "Hello World"

boolean {true, false}

decimal 7.08

float 12.56E3, 12, 12560, 0, -0, INF, -INF, NAN

double 12.56E3, 12, 12560, 0, -0, INF, -INF, NAN

duration P1Y2M3DT10H30M12.3S

dateTime format: CCYY-MM-DDThh-mm-ss

time format: hh:mm:ss.sss

date format: CCYY-MM-DD

gYearMonth format: CCYY-MM

gYear format: CCYY

gMonthDay format: --MM-DD

gDay format: ---DD (note the 3 dashes)

gMonth format: --MM--

hexBinary a hex string

base64Binary a base64 string

anyURI http://www.xfront.com

QName a namespace qualified name

NOTATION a NOTATION from the XML spec

Built-in datatypesDerived

normalizedString A string without tabs, line feeds, or carriage returnstoken String w/o tabs, l/f, leading/trailing spaces, consecutive spaceslanguage any valid xml:lang value, e.g., EN, FR, ... IDREFS must be used only with attributesENTITIES must be used only with attributesNMTOKEN must be used only with attributesNMTOKENS must be used only with attributesName NCName part (no namespace qualifier)ID must be used only with attributesIDREF must be used only with attributesENTITY must be used only with attributesinteger 456nonPositiveInteger negative infinity to 0negativeInteger negative infinity to -1long -9223372036854775808 to 9223372036854775808 int -2147483648 to 2147483647short -32768 to 32767byte -127 to 128nonNegativeInteger 0 to infinityunsignedLong 0 to 18446744073709551615unsignedInt 0 to 4294967295unsignedShort 0 to 65535unsignedByte 0 to 255positiveInteger 1 to infinity

Attributes We take the html img attributes <ATTLIST img

src CDATA #REQUIREDalt CDATA #REQUIREDheight CDATA #IMPLIEDwidth CDATA #IMPLIED>

<xs:element name="img"> <xs:complexType> <xs:attributeGroup ref="attrs"/> <xs:attribute name="src" use="required" type="URI"/> <xs:attribute name="alt" use="required" type="Text"/>

<xs:attribute name="height" type="Length"/> <xs:attribute name="width" type="Length"/> </xs:complexType></xs:element>

schema

Technology

xml schema vocabulary

simple type elements

complextype elements

type of content

xml instance document

child elements

schema authors

named type