SEKE 2012 Proceedings - Knowledge Systems Institute

fying the equivalences between concepts, associating them
in those three models. For example: a) the XML element
Writer is equivalent to the OWL concept Author that
is represented by the table Author; b) the XML element
name is equivalent to the OWL concept fullName that is
represented by the column fullName;
The output of the first level is the mapping file (XML
OWL RDB (Relational Database) Mapping). The XML descriptor
is an auxiliary file created by the programmer using
the Castor library. Section 6 describes further details.
The third level is in charge of interpreting the mapping
file with the XML descriptor. As a result, objects are created
in the level 4. The manager is responsible for interpreting
the XML files according to the mapping objects. If
a conflict occurs, conflict resolution becomes necessary to
resolve the data inconsistency. Section 5 addresses specifically
about the conflicts that can occur between XML files.
With the mapping objects in memory, the manager is responsible
for creating the header objects for the inclusion
into the DB along with the respective tuples, as shown in
Figure 3. Finally, level 5 generates the DML 1 file to insert
the content of XML instances into tables and columns.
Figure 3. Header layout
Next we present the input artifacts produced by OntoGen
(ontology) and OntoRel (relational schema), as well as three
XML documents. These artifacts are important for understanding
the XMap approach and the remaining paper.
4.1 Input Artifacts
Each XML file can have a particular structure. Figure 4
illustrates three XML files that contains data about authors,
publications and institutions. Although these files belong to
the same application domain (published papers in scientific
events), they have some structural differences, such as:
• On documents “A” e “C” (line 10), the author concept
is ; on document “B” (line 10), the same
concept is ;
• On document “A” (line 10), the concept author is lexical
2 ; on documents “B” e “C” (line 10), this concept
is non-lexical 3 ;
1 DML - Data Manipulation Language.
2 Atomic elements directly represented in computer, such as a string.
3 Complex element, such as an author composed by name and address.
Figure 4. Sample XML documents
Querying data in such heterogenous structure would require
individual extraction processes that could represent a
bottleneck to the system. To store the content of these files
into a RDB, our work uses a ontology as a global schema to
handle the structural distinctions between the documents.
Figure 5 shows the resulting OWL ontology, considering
the sample XML files as input to the OntoGen component.
Details of the ontology generation are found in [7].
Then the ontology is mapped to a relational schema by
the OntoRel component using some mapping rules:
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