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 multi-language compilation is provided. The system and method provide a mechanism for two or more separately written compiler components to co-operate in the compilation of mixed language compilation units. The system mitigates problems associated with conventional approaches to dealing with embedded code blocks. Extensibility is facilitated through the use of a common compiler infrastructure (CCI) in the form of a base class library. Compilers for specific languages are written as extensions of these classes. Common conventions and a flexible extensibility mechanism facilitate cooperation amongst the compilers.

Abstract: A system and method for enriching object oriented programming languages by employing XML literals, embedded expressions, and a flexible validator is provided. Object instantiation is accomplished by employing XML literals with optional embedded expressions. The XML literals themselves provide a means for concise programmatic denotation, which facilitates coding and debugging of XML data. XML embedded expressions, inter alia, allow complex objects to be constructed dynamically. The validation system and method provides flexible validation for the XML literals and embedded expressions using inference rules to describe when a literal expression is valid and what the resulting witness or proof is for the value denoted by the literal.