tion and restriction, in addition to supporting various built in simple types,
such as integer, float, date, and time.
The following convention applies to the rest of the chapter: The noun
schema or XML schema designates the grammar or schema to which an XML
document must conform and is used regardless of the actual schema language
(DTD, XSD, and so forth).
While XSD plays a major role in Web services,
Web services may still have to deal with DTD based schemas because of legacy
As an additional convention, we use the word serialization to refer to XML
serialization and deserialization. We explicitly refer to Java serialization when
referring to serialization supported by the Java programming language. Also note
that we may use the terms marshalling and unmarshalling as synonyms for
XML serialization and deserialization. This is the same terminology used by
XML data binding technologies such as JAXB.
4.1.2 XML Horizontal and Vertical Schemas
XML schemas, which are applications of the XML language, may apply XML to
horizontal or vertical domains. Horizontal domains are cross industry domains,
while vertical domains are specific to types of industries. Specific XML schemas
have been developed for these different types of domains, and these horizontal and
vertical applications of XML usually define publicly available schemas.
Many schemas have been established for horizontal domains; that is, they
address issues that are common across many industries. For example, W3C speci
fications define such horizontal domain XML schemas or applications as Exten
sible HyperText Markup Language (XHTML), Scalable Vector Graphics (SVG),
Mathematical Markup Language (MathML), Synchronized Multimedia Integra
tion Language (SMIL), Resource Description Framework (RDF), and so forth.
Likewise, there are numerous vertical domain XML schemas. These schemas
or applications of XML define standards that extend or apply XML to a vertical
domain, such as e commerce. Typically, groups of companies in an industry
develop these standards. Some examples of e commerce XML standards are Elec
tronic Business with XML (ebXML), Commerce XML (CXML), Common Busi
ness Language (CBL), and Universal Business Language (UBL).
When designing an enterprise application, developers often may define their
own custom schemas. These custom schemas may be kept private within the
enterprise. Or, they may be shared just with those partners that intend to exchange