1. Introduction to XML Schema DoD Users Group Tutorial on XML and Science
June Austin TX
Geoffrey Fox and Bryan Carpenter
PTLIU Laboratory for Community Grids
Informatics, (Computer Science , Physics)
Indiana University
Bloomington IN 47404
11/19/2018
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2. Outline
Our XML Schema discussion are based on excellent W3C document
Note that this is reasonably complete – parts 1 and 2 ( etc.) are more formal discussions not extensions in coverage
See (elementary) and note very complete tutorial and examples at
We only summarize the following topics in this primer
Basic Schema
XML Types
Namespaces
The important topics below are NOT discussed
Groups ** REMOVED
Include ** REMOVED
Derived types ** REMOVED
Import ** REMOVED
Remember: Schema and DTD are like classes in Java
XML files are instances of objects defined in Schema or DTD’s
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3. XML Schema PO Example po.xml I
<?xml version="1.0"?>
<purchaseOrder orderDate=" ">
<shipTo country="US">
<name>Alice Smith</name>
<street>123 Maple Street</street>
<city>Mill Valley</city>
<state>CA</state>
<zip>90952</zip>
</shipTo>
<billTo country="US">
<name>Robert Smith</name>
<street>8 Oak Avenue</street>
<city>Old Town</city>
<state>PA</state>
<zip>95819</zip>
</billTo>
Need to add mechanism (namelist) to associate schema with this XML
instance
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4. XML Schema PO Example po.xml II
<comment>Hurry, my lawn is going wild!</comment>
<items>
<item partNum="872-AA">
<productName>Lawnmower</productName>
<quantity>1</quantity>
<USPrice>148.95</USPrice>
<comment>Confirm this is electric</comment>
</item>
<item partNum="926-AA">
<productName>Baby Monitor</productName>
<USPrice>39.98</USPrice>
<shipDate> </shipDate>
</items>
</purchaseOrder>
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5. The Purchase Order Schema, po.xsd I
<xsd:schema xmlns:xsd="
<xsd:annotation>
<xsd:documentation>
Purchase order schema for Example.com.
Copyright 2000 Example.com. All rights reserved.
</xsd:documentation>
</xsd:annotation>
<xsd:element name="purchaseOrder" type="PurchaseOrderType"/>
<xsd:element name="comment" type="xsd:string"/>
<xsd:complexType name="PurchaseOrderType">
<xsd:sequence>
<xsd:element name="shipTo" type="USAddress"/>
<xsd:element name="billTo" type="USAddress"/>
<xsd:element ref="comment" minOccurs="0"/>
<xsd:element name="items" type="Items"/>
</xsd:sequence>
<xsd:attribute name="orderDate" type="xsd:date"/>
</xsd:complexType>
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6. The Purchase Order Schema, po.xsd II
<xsd:complexType name="USAddress">
<xsd:sequence>
<xsd:element name="name" type="xsd:string"/>
<xsd:element name="street" type="xsd:string"/>
<xsd:element name="city" type="xsd:string"/>
<xsd:element name="state" type="xsd:string"/>
<xsd:element name="zip" type="xsd:decimal"/>
</xsd:sequence>
<xsd:attribute name="country" type="xsd:NMTOKEN"
use="fixed" value="US"/>
</xsd:complexType>
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7. The Purchase Order Schema, po.xsd III
<xsd:complexType name="Items">
<xsd:sequence>
<xsd:element name="item" minOccurs="0" maxOccurs="unbounded">
<xsd:complexType>
<xsd:element name="productName" type="xsd:string"/>
<xsd:element name="quantity">
<xsd:simpleType>
<xsd:restriction base="xsd:positiveInteger">
<xsd:maxExclusive value="100"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
<xsd:element name="USPrice" type="xsd:decimal"/>
<xsd:element ref="comment" minOccurs="0"/>
<xsd:element name="shipDate" type="xsd:date" minOccurs="0"/>
</xsd:sequence>
<xsd:attribute name="partNum" type="SKU"/>
</xsd:complexType>
Anonymous type quantity
Specify item
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8. The Purchase Order Schema, po.xsd IV
</xsd:element> <!– End item specification 
</xsd:sequence> <!– End sequence for items specification 
</xsd:complexType> <!– End items specification 
<!-- Stock Keeping Unit, a code for identifying products -->
<xsd:simpleType name="SKU">
<xsd:restriction base="xsd:string">
<xsd:pattern value="\d{3}-[A-Z]{2}"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:schema>
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9. Comments on po.xsd I
The prefix xsd: is Namespace specified by xmlns:xsd=“
The label xsd is conventional; you could use a different one
Schema does two types of things:
Defines new types of elements or attributes e.g. PurchaseOrderType with xsd:complexType or xsd:simpleType
Defines internal elements and attributes for tags e.g. PurchaseOrder using xsd:element and xsd:attribute
So an element like shipTo in po.xml has at most one attribute country which if it appears must have value US. The elements name, street, city, state, zip must appear in this order and the first four are strings; zip is a xsd:decimal
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10. Comments on po.xsd II
The prefix xsd: is Namespace specified by xmlns:xsd=
The label xsd is conventional; you could use a different one
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11. Comments on po.xsd III Schema does two types of things:
Defines new types of elements or attributes e.g. PurchaseOrderType with xsd:complexType
Defines internal elements and attributes for tags e.g. PurchaseOrder using xsd:element and xsd:attribute
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12. Comments on po.xsd IV
So an element like shipTo in po.xml has at most one attribute country which if it appears must have value US. The elements name, street, city, state, zip must appear in this order and the first four are strings; zip is a xsd:decimal
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13. xsd:complexType Example
Anything of PurchaseOrderType is allowed one attribute (orderDate) of type xsd:date.
Further it must consists of 4 elements shipTo, billTo, comment and items in that order
comment can be absent as minOccurs = 0
Note that comment is a global element defined in the schema. It is accessed by ref= rather than type=
One can define global elements or attributes which cannot themselves use ref (global elements are particularly important if one imports this schema into other schema as only global components can be re-used)
minOccurs and maxOccurs have default values of 1 and so shipTo, billTo and items must appear once and once only
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14. Specifying xsd:element and xsd:attribute
Any xsd:element tag can have attribute minOccurs, maxOccurs, fixed and default
Any xsd:attribute can have attribute use and value
Note attributes can NEVER appear more than once
- means not present
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15. Simple Types
Attributes must be Simple Types; Elements can be complex types or simple types
Simple types cannot themselves have attributes or contain other elements
The xsd:restriction tag allows you to build new simple types by adding constraints to existing simple types. These constraints are specified by a set of “constraining facets”
xsd:minInclusive and xsd:maxInclusive restrict <= myInteger <= 99999
xsd:pattern restricts using a regular expression to 3 single digits followed by two capital letters
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16. Constraining Facets
These are defined in and are
length, minLength, maxLength, pattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minExclusive, minInclusive, precision, scale, encoding, duration, period
Tables tell you which constraining facets can be used with which simple type
enumeration can be used with all simple types except boolean. In example below, you could define a USState simple type which could take any of conventional abbreviations of the US States
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17. Simple Types Built In to XML Schema I
Simple Type Examples (delimited by commas) Red is Note
string Confirm this is electric
CDATA Confirm this is electric (white space(tabs) to blanks etc.)
token Confirm this is electric (trailing/leading white space removed)
byte , 126
unsignedByte , 126
binary E617279
integer , -1, 0, 1,
positiveInteger ,
negativeInteger , -1
nonNegativeInteger 0, 1,
nonPositiveInteger , -1, 0
int ,
unsignedInt ,
long ,
unsignedLong ,
short , 12678
unsignedShort , 12678
Lots of Types but no complex or Array Extensions of XML such as SOAP (W3C) or XSIL (HPCC) define additional types
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18. Simple Types Built In to XML Schema II
decimal , 0, 123.4,
float INF, -1E4, -0, 0, 12.78E-2, 12, INF, NaN
double INF, -1E4, -0, 0, 12.78E-2, 12, INF, NaN
boolean true, false
time :20:00.000, 13:20: :00
timeInstant T13:20: :00 [May 31st 1999 at 1.20pm Eastern Standard Time which is 5 hours behind Coordinated Universal Time]
timePeriod T13:20
timeDuration P1Y2M3DT10H30M12.3S [1 year, 2 months, 3 days, 10 hours, 30 minutes, 12.3 seconds]
date
month [May 1999]
year [1999]
century [the 1900's]
recurringDay [every 31st day]
recurringDate [every May 31st]
recurringDuration T13:20: [May 31st every year at 1.20pm Coordinated Universal Time, format similar to timeInstant]
Red is Note
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19. Simple Types Built In to XML Schema III
Simple Type Examples (delimited by commas) Notes in []
Name shipTo [XML 1.0 Name type]
QName po:USAddress [XML Namespace QName]
NCName USAddress [XML Namespace NCName, i.e. a QName without the prefix and colon]
uriReference
language en-GB, en-US, fr [valid values for xml:lang as defined in XML 1.0]
ID [XML 1.0 ID attribute type]
IDREF [XML 1.0 IDREF attribute type]
IDREFS [XML 1.0 IDREFS attribute type]
ENTITY [XML 1.0 ENTITY attribute type]
ENTITIES [XML 1.0 ENTITIES attribute type]
NOTATION [XML 1.0 NOTATION attribute type]
NMTOKEN US, Brésil [XML 1.0 NMTOKEN attribute type]
NMTOKENS US UK, Brésil Canada Mexique [XML 1.0 NMTOKENS attribute type, i.e. a whitespace separated list of NMTOKEN's]
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20. Schema and Namespaces
Schema do a better job than DTD in making it clear how Namespaces can be used effectively
Here we define as the targetNamespace for this schema
We also define po: as the same URL and the default Namespace to be W3C Schema central
Then we do NOT need xsd: as in original po.xml as we have set Schema central to be default
In name=‘..’, we do NOT need to specify a Namespace but in type=“..” or ref=“..” we do not as these could reference another Namespace
Namespace po:
No Namespace as string type define in Schema Central
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