Techniques are disclosed for retrieving both data stored in relational form and data stored in XML form responsive to a single XQuery query. The techniques allow applications to retrieve relational data residing in various relational database management systems by using XQuery and XQuery for Java. In one such embodiment, an embeddable serverless computer component implements the techniques, and includes a combination of one more relational adaptors and a mediator to access relational data and transform it into appropriate XML. The techniques are embeddable, and can be standards-based, database-independent, and operating-system independent. Optimized performance and scalability from desktop to enterprise applications are enabled as the number of users and/or database size increases.