Trends in Data Mining and Knowledge Discovery - Advanced Techniques in Knowledge Discovery and Data Mining - page 12

object-oriented model (examples include eXcelon, X-Hive, and ozone). There
are also XML-native DBMS, that are not built on either relational or object-
oriented models. They are schema-independent, information-centric, and
characterized by treating context as flexibly as the data. Example of such a
DBMS is the NeoCore's XML database [50].
z The XML-enabled DBMS incorporates the XML document into the traditional
database technology. Examples of commercial XML-enabled DBMSs (all use
the relational model) are: Oracle 8i [7], DB2 [23], Informix [41], Microsoft
SQLServer 2000 [68], and Microsoft Access2002 [74]. Because these systems
are used on a large scale in the business world they may become a dominant
method for storing XML documents.
However, there are several problems associated with using XML-enabled
DBMS. First, the existing models of storing XML documents do not fully
preserve the context of the XML documents (e.g., the order of tags is lost).
Second, some content, like comments or processing instructions of the XML
document, is also lost. In contrast, any native XML DBMS preserves that
information. The researchers already developed some solutions to this
problem by proposing new schemas for storing XML documents within both
relational and object-relational DBMS, which either use [9], [64], or do not
use the Document Type Definition (DTD) documents [65].
Another advantage of XML is the ability to query it to retrieve and
manipulate data stored in the document. A number of query languages have been
developed, including Lorel [1], Quilt [20], UnQL [14], XDuce [40], XML-QL [27],
XPath [24], XQL [60], Xquery [21], and YaTL [25]. XPath and Xquery are two
query languages that received the W3C recommendation.
1.3.2. XML-RPC
XML-RPC (XML-Remote Procedure Call) is a protocol that allows software
running on disparate operating systems and in different environments to make
procedure calls over the Internet [75]. It uses HTTP as the transport and XML for
the encoding. XML-RPC is designed to be as simple as possible to allow for the
transmittal, processing, and return of complex data structures. XML-RPC
implementations are available for virtually all operating systems, programming
languages, dynamic and static environments, which include implementations in
Perl, Python, Java, Frontier, C/C++, Lisp, PHP, Microsoft .NET, Rebol, Real Basic,
Tcl, Delphi, WebObjects, and Zope.
1.3.3. SOAP
SOAP (Simple Object Access Protocol) is another XML/HTTP-based protocol for
accessing services, objects, and servers on the Internet [66]. It is platform-
independent. It consists of three parts: an envelope that defines a framework for
describing what is in a message and how to process it, a set of encoding rules for
expressing instances of application-defined data types, and a convention for
representing remote procedure calls and responses. SOAP is derived from XML-