Abstract: An object-oriented programming language with integrated query powers for both SQL and XML is disclosed. Portions of SQL select statement as well as XPath have been tightly integrated into a compiler and type system to provide for strongly typed programming and seamless access to both SQL and XML data.

Abstract: A type system employing structural subtyping is disclosed herein. A core type system supports several structural types, such as stream, choice, intersection and sequence. Also part of the core type system is a new invariant type, which denotes values whose dynamic type is the same as its static type, and type restrictions for limiting a range of a base type. Furthermore, a streamlined structural version of delegates, called structural delegates and a validation method thereof are introduce into the type system. To further facilitate type safety, strict statically checked interface casts are introduced.

Abstract: A system and method for interfacing additional translation logic via composer(s) to a compiler to extend the capabilities of the compiler is provided. Generally, composer(s) can be software libraries that provide employment of componentization and polymorphism to compiler add-ons in order to extend compiler capabilities. One or more composers can be accessible to the compilation process by reference(s) made in a source code file. For example, additional translation logic for data types and/or expressions (e.g., markup language) created after compiler design can be made accessible to a compiler via composer(s), thus extending the existing compiler. The present invention mitigates problems associated with conventional compiler extending schemes and affords for compile code optimization without having to consider substantially all of the operations of a single query.