1. XML Data Reduced Schema
Eugenia Fernandez
IUPUI

2. Problems with DTDs
Not expressed in XML syntax – must learn new language
Little control over data types
Not easily extensible
Does not support XML namespaces, thus cannot mix elements from multiple sources

3. History of XDR Based on a submission to the W3C
Subset of Microsoft’s full XML-Data recommendation
Proposal submitted in January 1998 before XML 1.0 standard was done
Integral part of BizTalk, an XML vocabulary used for e-commerce

4. XDR Schema Root element is always Schema Root element always contains
a name attribute that specifies the name of the schema
an xmlns attribute that specifies the default namespace for the Schema element and its child elements

5. xmlns:dt="urn:schemas-microsoft.com:datatypes">
XDR Schema Element
<Schema name="myschema"
xmlns="urn:schemas-microsoft.com:xml-data"
xmlns:dt="urn:schemas-microsoft.com:datatypes">
. . .
</Schema>

6. XDR Element Syntax <ElementType
content="{empty | textOnly | eltOnly | mixed}"
dt:type="datatype"
model="{open | closed}"
name="idref"
order="{one | seq | many}">

7. ElementType Content empty textOnly eltOnly only other elements mixed
mixed content model

8. Linking an XDR Schema to an XML Document
Add xmlns attribute to root element
<root_element xmlns = x-schema:filename.xdr">
</root_element>

9. Element Datatypes boolean char date dateTime float int number string
fixed.14.4
i1, i2, i4, i8
r4, r8
ui1, ui2, ui4, ui8
uri
For a complete list, go to

10. ElementType Model Open Closed
can contain other elements & attributes not specified in the schema
Closed
cannot include elements or other content not specified in the schema

11. ElementType Name
name="idref"
required,
identifies the element

12. ElementType Order Establishes the order of the child elements One Seq
only one element of the set can be included
Seq
elements must appear in the specified sequential order
Many
elements may appear, or not, in any order

13. Declaring Child Elements
use element tag nested within ElementType tag with name of child element contained in type attribute
a matching ElementType must exist for the child element
<ElementType name="parent" model="closed" content="eltonly"> <element type="child"/> </ElementType>
<ElementType name="child" model="closed" content="textOnly"/>

14. Declaring Attributes
Add AttributeType element as a child of the element to which the attribute belongs
declares a type of attribute
Pair it with an attribute element
defines an attribute for that particular element

15. AttributeType Syntax <AttributeType default="default_value"
dt:type="primitive-type"
dt:values="enumerated-values"
name="idref"
required="{yes | no}">

16. AttributeType dt:types
entity
entities
enumeration id
idref
idrefs
nmtoken
nmtokens
notation
string

17. Attribute Element Syntax
overrides any default provided in AttributeType
<attribute
default="default_value"
type="attribute-type"
[required="{yes | no}"] >
must match name attribute of previously declared AttributeType
optional if required attribute used in AttributeType

18. Occurrence Indicators
via child elements of the element tag
<element
type="element-type"
[minOccurs="{0 | 1}"]
[maxOccurs="{1 | *}"] >
optional
required
only once
many times

19. Attribute Length Constraints
for attributes with dt:type of string or number
via attribute of AttributeType element
dt:minLength="positive-integer"
dt:maxLength="positive-integer"

20. Content Groups
Establishes constraints on a group of child elements within an ElementType element
<group order="{one | seq | many}"
minOccurs="{0|1}" maxOccurs="{1|*}"
<element type="ElementType"/>
</group>

21. References
Day 5 in Sams Teach Yourself XML in 21 Days, Second Edition (Sams Publishing, 2001)