The Third Manifesto: Meaning (information, definition, explanation, facts)

The Third Manifesto (1995) is Christopher J. Date's and Hugh Darwen's proposal for future relational database management systems that would avoid 'impedance mismatch' between object-oriented programming languages and RDBMSs by fully supporting all the capabilities of the relational model.

The main objective of The Third Manifesto, besides being theoretically sound and avoiding arbitrary restrictions and pragmatic debasement of the relational model, is to make a simple, restricted and precise definition of the role of object orientation in Database Management systems emphasising the few valid ideas from object modelling that are orthogonal to relational modelling. One of the major tasks has been to illustrate ways in which SQL represents an inadequate reflection of the relational model.

It illustrates the relational model using their own database language, Tutorial D, for which there are several partial implementations, including:

• Alphora Dataphor, a commercial product which implements the language atop SQL databases
• Rel, an Open Source implementation in Java