In this paper we will try to answer to some questions referring to hypertext. In the same time our purpose is to explain what we mean by a query in the context of XQL, and to present a simple model, which will serve as a framework for the future research.techniques, XML, XQL, query, data mining

Loredana MOCEAN

English

Research Papers in Economics

Informatica Economică, nr. 2 (42)/2007 
 
78 
Data Mining Techniques of  XML Data Warehouse 
 
Loredana MOCEAN 
Babeş - Bolyai University of Cluj – Napoca 
 Business Information Systems Department 
mloredana@econ.ubcluj.ro 
 
In this paper we will try to answer to some questions referring to hypertext. In the 
same time our purpose is to explain what we mean by a query in the context of XQL, and to 
present a simple model, which will serve as a framework for the future research. 
Keywords. techniques, XML, XQL, query, data mining. 
 
Introduction 
A
hyper
n important part of the advantages of 
text against the print text are: 
• Nonlinear form of the hypertext offers  ef-
ficient capabilities of go through the con-
tents; 
• Electronically medium can stock an impor-
tant quantity of information; 
• Hypertext offers  a better visualization of 
the content and a rapid navigation, however 
complex would be the documents,  taking 
count of the specifications of the users; 
• The queries, filters, different preferences 
and annotations of the users cane be re-use 
whenever need, and can be stored as part of 
the hypertext structure of the used docu-
ments. 
2. Results and discussions 
The main problems wherewith the program-
mers are confronted in what looks the hyper-
text, are: 
• The conversion, automatically in general, 
of the plain text in hypertext format; 
• The linearization of hypertext; 
• The design of hypertext documents; 
• The concurrent accessing of hypertext da-
tabase in distributed context; 
• The building of some optimal mechanisms 
for intelligent searching and querying  of the 
hypertext information; 
• The supporting of the multimedia exten-
sions; 
• The presenting of the hypertext documents 
in an easy shape for the users. 
An hypertext system is compound by nodes 
(concepts) and links (relationships). A node 
represents a unique concept (an idea) and 
may contain any type of information (text, 
graphics, animation, audio, video, images or 
prams).  
All these elements has associated a type (de-
tail, proposition, collection, observation etc.), 
a semantic information. The nodes are con-
nected with other nodes through the links. 
The source node is called reference and the 
destination node is called referent or an-
chors. 
The modality of stocking the information in 
the nodes varies from system to system, but 
the most used techniques use the markup 
languages (SGML - Standard Generalized 
Markup Language and XML - Extensible 
Markup Language), the current standards 
built on these languages are HyTime (Hy-
permedia/Time- based Structuring Lan-
guage), MHEG (Multimedia and Hypermedia 
Information Coding Expert Group), HTML 
(HyperText Markup Language).  
The major advantage is assuring of hardware 
and software platform independence, the 
owner format lead to difficulty in navigation, 
search or support. Once, the nodes can con-
tains multimedia information, the hyperme-
dia systems must be sufficiently of flexible 
for supporting many graphical, audio and 
video formats. 
The next problems we want to discuss are the 
query languages for XML.  We are interest in 
that because we want to structure the data for 
the Web and to see the information in easy 
form and reports. 
The solution is XML and, in achieving this 
desideratum, we can use two important tech-
niques: 
1 Informatica Economică, nr. 2 (42)/2007 
 
79
  The mark of web information : stocking, 
formalization and transforming; 
  The search upon different criteria: XML 
based languages for making queries. 
The XML is the standard meta-language for 
annotation the WEB and has some important 
properties: 
  The requirement of offering formal defi-
nitions for all the used concepts; 
  Possibilities of automatic processing; 
  Inherent efforts of development of some 
specialized techniques and languages in in-
dex and query of the contents of web docu-
ments; 
We can see the web pages as XML docu-
ments. As we know, documents can contains 
many characters. The most important things 
of which we abide are: 
  The extracting of the data from very ex-
tensive documents, in which we process the 
structural part and the plain text; 
  The transfer of XML documents between 
documents with different ontologies; 
  The integration of data which are gath-
ered from multiple sources; 
  The transmitting of large quantities of 
XML data to users; 
  Techniques of transmitting of queries to 
XML resources. 
It is sometimes necessary to extract subsets 
of the data stored within an XML document. 
A number of languages have been created for 
querying XML documents. The most impor-
tant methods of querying are: 
1.  The selection based on keywords; 
2.  The extrapolation of the methods of inter-
rogate the databases, inclusively relational ( 
with Web3QL, WebSQL, XQL, XML-QL ); 
3.  Graphical modeling of search demands 
with XMLGL, WQGL, WQFL; 
4.  Re-iteration of previous navigation. 
The requirements are shown in figure 1. 
 
 
 
 
 
 
 
 
 
QUERIES 
The syntax of queries 
•  well defined 
•  unambiguous 
•  exhaustive 
The modeling of queries 
•  XML documents 
•  Compliance with DTD 
The results of queries 
•  Xml documents 
•  Compliance with  
DTD 
 
Fig.1. The requirements of correct queries 
 
XQL was designed as a general-purpose 
query language for XML. During the design 
of the language, four big types of queries 
were designed to determine the requirements, 
as we see in table 1. 
 
Name  Type  Characteristics  Describe  
Q1  Query 
within a 
single 
document 
- used in scripting languages 
- may define different access right 
- provide powerful non-
procedural access to document 
- the name of elements 
- the name of attributes 
- the type of a node 
- the content of the node 
- the relationships between nodes 
Q2  Query 
within col-
lections of  
documents 
- used in document assembly 
- used in queries performed on a 
single website or across websites 
- used in scripting languages to 
provide powerful non-procedural 
access to document data  
- a set of documents or a set of nodes 
within multiple documents 
- need to be able to address the indi-
vidual documents Informatica Economică, nr. 2 (42)/2007 
 
80 
Q3  Addressing 
within or 
across 
documents 
- used for referencing known lo-
cations in documents using hyper-
links 
- allow anchors to be placed 
within documents 
- address any node in the docu-
ment 
- specifies relative and absolute 
path in the document 
- the name of elements 
- the name of attributes 
- the type of a node 
- the content and value of the node 
- the relationships between nodes by 
the above criteria, including hierar-
chy, sequence and position  
Q4  XSL Pat-
terns 
- used to specify tree-to-tree 
transformations on documents 
- the name of elements 
- the name of attributes 
- the type of a node 
- the content of the node 
- the relationships between nodes 
Table 1. Types of queries in XQL 
 
Query language should be useable in a vari-
ety of environments: in programming lan-
guage and scripting language strings, in 
URLs, and as attributes in documents or XSL 
templates. XQL queries can easily be typed 
as strings on a command line, generated by 
graphical query interfaces, or embedded as 
strings in programs.  
As an example, we propose to write a query 
that returns Nrfactura that are children of 
Facturi elements, in different ways, to be ex-
amples for implementing: 
 
Query method  Query description 
XQL query  Facturi/Nrfactura 
Java String  String qstring = Facturi/Nrfactura; 
As a part of an URL  http://www.bazadedate.com/docs#Facturi/Nrfactura 
Embedded in attrib-
utes of HTML or 
XML documents  
<a href>=”http://www.bazadedate.com/docs#Facturi/Nrfactura”> 
Table 2. Examples of query methods 
 
In XQL we operate with the following con-
cepts: 
  The database is a set of one or more 
XML documents; 
  Queries are done in XQL, a query lan-
guage that uses the structure of XML as a ba-
sic model; 
  A query is given a set of input nodes 
from one or more documents, and examines 
those nodes and their descendants; 
  The result of a query is a set of XML 
document nodes, which can be wrapped in a 
root node to create a well-formed XML 
document. 
We will try to illustrate some of these con-
cepts. The input to the query is <Facturi> 
element, which is the root of the main docu-
ment. The search context is: 
<Facturi> 
  <Campuri> 
<NrFactura>1000</NrFactura> 
<DataFactura>12.01.2007</DataFactura> 
<IdPartener>100</IdPartener> 
<TipFactura>I</TipFactura> 
  </Campuri> 
  <Indecsi> 
<NrFactura>1000</NrFactura> 
<IdPartener>100</IdPartener> 
  </Indecsi> 
</Facturi> Informatica Economică, nr. 2 (42)/2007 
 
81
 
The result of the query <Facturi>, is the 
set of all <Facturi> elements in the search 
context. In our example, the result set is 
equivalent to the search context, the previous 
document, the same one. The search context 
and the result set contain one node each. 
The result set contains only one node. But a 
query returns more than one node, though, a 
text representation of the result set is not a 
well-formed XML document, because an 
XML document can have only one root node. 
We will do a more complicated query, using 
a wildcard, regardless of element name, and 
the parent/child operator (‘/’).  The following 
query searches for all children of <In-
decsi> elements which are children of   
<   elements:   Facturi>
Facturi/Indecsi/* 
The result set is: 
<NrFactura>1000</NrFactura> 
<IdPartener>100</IdPartener> 
 
This result set contains two nodes and it is 
not a valid XML document. We must wrap 
the nodes of the set in a common root ele-
ment. We will have a valid XML document. 
So, the result document of an XQL query al-
ways wraps the nodes of the result set in an 
<xql:result> element: 
<xql:result> 
<NrFactura>1000</NrFactura> 
<IdPartener>100</IdPartener> 
</xql:result> 
 
When a query has operators, evaluation be-
comes a more complex operation. When an 
operator is evaluated for a given search con-
text, it selects the appropriate search context 
for each of its operands. The search context 
for which an operand is evaluated need not 
be identical to the search context of the 
query.   
Most XQL expressions will evaluate either to 
a set of nodes or a Boolean value. All XQL 
query expressions may be said to evaluate to 
true or false.  
In XQL we can find two kinds of return op-
erators. The shallow return operator (“?”) re-
turns just the node to which it is applied. The 
deep return operator (“??”) returns the ele-
ment and all its children. Return operators 
can simplify queries for complex document 
structures. Here is an example for our discus-
sion of return operators: 
<?xml version=”1.0”> 
<DocumenteFacturate> 
<Facturi> 
<IdPartener>100</IdPartener> 
  <Campuri = 2> 
  <Intrare cantitate=1> 
<NrFactura>1000</NrFactura> 
<DataFactura=”12.01.2007”/> 
<TipFactura>I</TipFactura> 
  </Intrare> 
  <Intrare cantitate=2> 
<NrFactura>1001</NrFactura> 
<DataFactura=”12.01.2007”/> 
<TipFactura>I</TipFactura> 
  </Intrare> 
</Facturi> 
<Facturi> 
<IdPartener>101</IdPartener> 
  <Campuri = 2> 
  <Intrare cantitate=1> 
<NrFactura>1002</NrFactura> 
<DataFactura=”13.01.2007”/> 
<TipFactura>I</TipFactura> 
  </Intrare> 
  <Intrare cantitate=2> 
<NrFactura>1003</NrFactura> 
<DataFactura=”13.01.2007”/> 
<TipFactura>I</TipFactura> 
  </Intrare> 
  </Campuri> 
</Facturi> 
<Indecsi> 
<NrFactura>1000</NrFactura> 
<IdPartener>100</IdPartener> 
</Indecsi> 
</DocumenteFacturate> 
 
We want to see all the entries (the date of the 
document) which is recorded on an element 
called Facturi. We can successfully use the 
following query: 
Facturi//DataFactura 
The results for the above query are shown 
bellow: 
<xql:result> 
<DataFactura=”12.01.2007”/> 
<DataFactura=”12.01.2007”/> 
<DataFactura=”13.01.2007”/> 
<DataFactura=”13.01.2007”/> 
</xql:result> 
 
A shallow return ("?") on the <Factura> 
element returns the <Factura> element, Informatica Economică, nr. 2 (42)/2007 
 
82 
providing an element within which the prod-
ucts can be listed: 
Facturi??//DataFactura 
These are the results: 
<xql:result> 
<Facturi> 
<DataFactura=”12.01.2007”/> 
<DataFactura=”12.01.2007”/> 
</Facturi> 
<Facturi> 
<DataFactura=”13.01.2007”/> 
<DataFactura=”13.01.2007”/> 
</Facturi> 
</xql:result> 
 
If we want to see the customer for each 
document <Factura>, the date and the Id 
number, this can be done by specifying both 
<DataFactura> and <IdPartener> using 
the deep return operator: 
Fac-
turi?[IdPartener??]//DataFactura?
? 
The results are: 
<xql:result> 
<Facturi> 
<IdPartener>101</IdPartener> 
<DataFactura=”12.01.2007”/> 
<DataFactura=”12.01.2007”/> 
</Facturi> 
<Facturi> 
<IdPartener>101</IdPartener> 
<DataFactura=”13.01.2007”/> 
<DataFactura=”13.01.2007”/> 
</Facturi> 
</xql:result> 
3. Conclusions 
As we saw in this paper, XQL is a query lan-
guage designed specifically for XML docu-
ments. In the same sense that SQL is a query 
language for relational database, XQL is a 
query language for XML documents. The ba-
sic constructs of XQL correspond directly to 
the basic structures of XML. Since queries, 
transformation patterns, and links are all 
based on patterns in structures found in pos-
sible XML documents, a common model for 
the query language used in these paper is 
both possible and desirable, and a common 
syntax to express the patterns expressed by 
that model simplifies the task of the user who 
must be able to use a variety of XML query 
technologies.  
We have described a few things about XQL, 
keeping in mind its continuity with relational 
database standards such as SQL. 
 
References. 
[Brut07] Brut M., Buraga S., Limbaje de in-
terogare XML, whitepaper, 2007 
[Buraga06] Buraga S., Tehnologii XML, Ed. 
Polirom, 2006 
[Buraga07] Buraga S., Incursiune în teoria 
hypetextului, whitepaper, 2007 
[Mocean06] Mocean L. (coord), ş.a., Baze de 
date şi programare – Culegere de probleme, 
Ed. Risoprint, Cluj – Napoca, 2006 
[Phillips01] Phillips L.A., XML, Ed. Teora, 
2001 
http://www.texcel.ro
 

Data Mining Techniques of XML Data Warehouse

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