There are no suitable repositories available satisfying the existing requirements of the domain around the Business Process Execution Language for Web Services (BPEL4WS, BPEL for short). This Master’s Thesis explores an object-oriented approach for providing data retrieval and querying services to other software. The BPEL repository is built on top of the Eclipse platform and it uses the Eclipse Modeling Framework (EMF) for handling the data persistence of objects as XML files.
Instead of using the native querying language of a database system, an objectoriented approach is utilized. The data is queried in EMF object representation. The Eclipse Modeling Framework takes care of converting the data from one form to another and transforming the data models to another.
The Object Constraint Language is used as an object-oriented querying language for the repository data. The power of an object-oriented approach is that only the object representation of data must be known when the queries are formulated. Programs use this object representation internally and thus, it is straightforward to construct queries for this data representation. It is not necessary to know how the data is stored, for example in a relational database, or in an XML database.
The querying performance of the BPEL repository scales linearly compared to the repository size, because all the queried files are loaded completely in a main memory, when the query is executed. No indexing mechanisms or other query speed-ups familiar from database systems are utilized. However, the querying mechanism scales well enough for the purpose it was created. Future work could explore how only the necessary parts of the files are loaded into objects using for example a lazy XML loading mechanism. Another option is to map the object-oriented queries to a query language provided by a database system.
By: J. Vanhatalo
Published in: RZ3582 in 2005
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