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semantic model way so as to alleviate the pressure of
application processing date.
B. XML Semantics
It is known that XML semantics is semantic
information in XML document.
As to information description, it is ideal to describe all
information with same syntax. As an effective way to
share the data among applications or machines, XML
makes it possible to put data with different types into
same format. While, the understanding to XML semantics
is different in different fields, among which, three such
understandings have solved different problems of XML.
1) Mapping to UML: Mapping XML document to
XML diagram as its semantics. MDL (Meaning
Definition Language) [8] is such a kind of language,
which chooses XML nodal points with Xpath expression
words and maps the points to UML object, attribute and
relation. While, XML data binding is a technique to map
XML document OO of object model.
2)Basing on format semantic way of procedure
language: XML semantics can be defined format
semantic way of procedure language, for example,
W3C[9] standard defines Xpath and Xquery operation
semantics with judge and inference rule; Wadler [10]
describes model semantic of Xpath and XSLT with
traditional referring semantics; Yang[l1]describes Xpath
semantics with formalizing standard language of Object-
Z.
3)Basing on attribute grammar: Finding the similarity
between XML marked document and character string
generated from BNF grammar, Psaila & Crespi-
Reghizzi[l2] put forward a way to transfer DTD element
description to formal EBNF rule and Semantics rule
definition (SRD) and gives an algorithm to calculate
XML relation semantics of the rule definition. After that,
Havasi[13] further advanced a new semantic rule
congregation and expression language of semantic rule
meta-language (SRML), which extend XML. Attribute
grammar checks semantic consistency by examining and
evaluating attribute value.
III.XML IMPLICIT SEMANTICS
Though having been the base of web technique
framework, with its application in data exchange and
application congregation, XML is more and more known
for its important shortage: expression only in data
grammar, not in formalizing semantics.
Basic XML idea: data in XML document is described
by labels in a meaningful and self-description way,
especially label names selected by experts [14]. The label
reflects common recognition. For example, label of
means the age which can be inferred that data
marked on the label refers to age. However, XML
including DTD or XML Schema does not give
formalizing system to explain what the label mean which
results in XML processor’s failure to understand what
label mean in XML document. In fact, there is no
difference in the meaning between label and
HTML label . That means XML shows grammar
rather than formalizing semantics.
While, XML label and XML document framework
contain some meaning, the label means something to
human beings, just like XML fragment:
Computer Network
Compulsor
expresses rich semantic information as follows: a
lecturer named “David Kevin” teaches a compulsory
course of “computer network”. The nest between nodal
points of lecturer and course shows a relation of professor.
Semantic information in XML document is called as
XML semantics [2]. XML semantics is expressed by
document framework and label such as element nest and
nest adjacency, and XML attribute. It is worthy to
mention, there is no corresponding rules to bind XML ’s
semantic expression way, so XML implicit semantic
expression ways are diverse with irregular formats, such
as nest and adjacency of node, and detailed meaning of
node order. So it is difficulty to automatically analyse and
extract relevant semantic information from XML
document.
IV.XML IMPLICIT SEMANTIC EXPRESSION MODEL
In fact, XML is designed to be a unified data format
and not suitable to show concept modal, which including
concept, attribute and their relation. However, when users
express data to XML document, data semantic
information has been in label and framework of XML
document such as element nest and adjacency, XML
attribute nodal order and ID / IDREF. But it is impossible
for the machine to understand semantic information;
furthermore, most semantic information has been lost.
However, XML has visual semantics; there is some
meaning in the label which means something to human
beings. In addition, XML document framework also
mean something and XML semantics is impliedly
expressed in XML document.
XML has rich semantic information and diversified
semantic expression ways, generally including word,
individual, and data attribute and object attribute of OWL
DL.
A. Expressions of words
In XML, word is generally showed by the value of text
node and XML attribute. If data pattern defined in XML
Schema, it corresponds to OWL pattern word. But
element sometimes can be expressed into character, say
as data attribute value, while these elements owns no
attributive node. For example, an XML document to
show students’ scores.
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