# Metrics-Based Comparison of OWL and XML for Representing and Querying Cognitive Radio Capabilities
## 2 Related Work
### Data Transformation between RDF/OWL and XML  
The related work in this category, further classified into three groups, (1) XML to RDF/OWL, (2) RDF/OWL to XML, and (3) bidirectional transformation, is summarized in Table 1. The values in the second column indicate the types of support used for the schema transformation with the lack of such support being indicated by \"N/A\".  
In the first group (XML to RDF/OWL), the methods that fully automate the transformation typically rely on predefined, generic mapping rules that are encoded as XSLT stylesheets [30]. While the research presented in [10; 11; 12; 15; 16; 23] relies on mappings developed at the schema level, in [17], mapping is defined at the data level. These transformations retain the original structure of the input XML, yielding RDF/OWL data that usually do not properly convey the intended semantics. Other methods in this group require either additional input or some form of user interaction. In [13; 14], a graphical interface is relied on by the users to define the schema mapping rules, and this produces an XSLT for automatic data transformation. In [18], a mechanism for extracting RDF/OWL data from XML is defined. This involves declaring that XML data are compatible with RDF/OWL via linking to algorithms (typically XSLT). In [20; 21], XML data are transformed to RDF by performing a depth-first search traversal of the XML tree. In addition to the XML data, in [19], ontology and a schema are required for ontology mapping by the user. In [22], user-provided mapping expressed in a domain-specific mapping language is employed.  
For the second group (RDF/OWL to XML), in [24], an extension to the XSLT function set was proposed. This allows SPARQL queries to be embedded into XSLT which, in turn, provides a new platform for scripting and transforming RDF into XML.  
For the third group (bidirectional), in [25], the transformation is provided based on the XML schema, and in [26], the RDF-based Semantic Mediation approach is used. In [27], mechanisms are provided for annotating XML schema elements (especially within WSDL definitions) that can be leveraged for automatic and bidirectional transformation. In [28; 29], XSPARQL, a combination of XQuery and SPARQL with one language first extracting the native input data through queries and the other used for transformation to the target language through update statements, is defined.  
The bidirectional methods are the most relevant to the work described in this paper, since they may better satisfy the fairness principle of the evaluation method (Section 1.2). However, in our work, instead of transforming between the two languages, we relied on the XML-based serialization of RDF/OWL, which can be treated as XML and RDF/OWL at the same time (Section 6).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Related Work** & **Schema Transformation** \\ \hline \multicolumn{3}{c}{(1) _XML_\(\rightarrow\)_RDF/OWL_} \\ \hline [PERSON] et al. [10] & XML Schema \(\rightarrow\) OWL-DL \\ [PERSON] et al. [11] & XML Schema \(\rightarrow\) OWL-FULL \\ [PERSON] et al. [12] & XML Schema \(\rightarrow\) OWL-DL \\ JXML2 OWL [13; 14] & N/A \\ DTD2 OWL [15] & DTD \(\rightarrow\) OWL-DL \\ \({}^{\star}\) [PERSON] et al. [16] & XML Schema \(\rightarrow\) OWL-DL \\ Breitling [17] & N/A \\ \({}^{\star}\) GRDDL [18] & N/A \\ \({}^{\star}\) XMLtoRDF [19] & N/A \\ \({}^{\star}\) [PERSON] et al. [20; 21] & N/A \\ XMLMaster [22] & N/A \\ EXCO [23] & XML Schema \(\rightarrow\) OWL-DL \\ \hline \multicolumn{3}{c}{(2) _RDF/OWL_\(\rightarrow\)_XML_} \\ \hline \multicolumn{3}{c}{(3) _Bidirectional_} \\ Gloze [25] & N/A \\ [PERSON] et al. [26] & XML Schema \(\rightarrow\) OWL-DL \\ \({}^{\star}\) SAWSDL [27] & N/A \\ \({}^{\star}\) XSPARQL [28; 29] & N/A \\ \hline \hline \end{tabular} \({}^{\star}\)Semi-automatic data transformation that requires user intervention.  
\end{table}
Table 1: Methods used for the transformation between RDF/OWL and XML.