132

Designing XML Based Applications

type derivation, XML schema design shares many of the aspects of object oriented

design especially with respect to modularization and reuse.

The design of domain specific XML schemas breaks down according to the

definition of XML schema types, their relationship to other types, and any con 

straints to which they are subjected. The definitions of such XML schema types,

relationships, and constraints are typically the result of the analysis of the applica 

tion domain vocabulary (also called the business vocabulary). As much as possi 

ble, schema designers should leverage already defined public vertical domain

schema definitions to promote greater acceptance and interoperability among

intended participants. The designers of new schemas should keep interoperability

concerns in mind and try to account for reuse and extensibility. Figure 4.2 shows

the UML model of a typical XML schema.

anyType

lineItem

categoryId

productId

itemId

lineNo

quantity

unitPrice

UserId

LineItems

ShippingDate

OrderDate

OrderID

1

1

1

1

decimal

positiveDecimal

Invoice

Figure 4.2

Model for an XML Schema (

Invoice.xsd

)