The system essentially offers the following set of features (the set of accessible features depends on a specific user role):

• User authentication
• Storage, update, and download of EEG/ERP data and metadata
• Storage, update and download of EEG/ERP experimental design (experimental scenarios)
• Storage, update and download of data related to testing subjects
• Fulltext search
• Sharing of knowledge and working in groups

The system is based on tree layer architecture (MVC pattern) consisting of persistent layer (relational database), application layer (object oriented code, object relational mapping from persistence layer) and presentation layer (JSP). The persistence layer uses Hibernate framework; Oracle 11g database server is used to ensure the processing of large data files. Application and presentation layers are designed and implemented using Spring technology. This framework supports MVC architecture, Dependency injection and Aspect Oriented Programming. There were no significant difficulties with integration of both frameworks, Hibernate and Spring MVC. Spring Security framework is used to ensure management of authentication and user roles.

Since the system is thought to be finally open to the whole EEG/ERP community it is necessary to protect EEG/ERP data and metadata, and especially personal data of testing subjects stored in the database from an unauthorized access. Then a restricted user policy is applied and user roles are introduced.

The complete overview of the system features and user roles (use case diagram) is available in (Pergler 2009). Concerning the architectural layers there is a question which layer is more feasible for mapping of its structure into ontology.

Currently we have studied two possibilities:

• Mapping from the persistence layer (relational database)
• Mapping from the application layer (object oriented code)