"The Semantic Web is about two things. It is about common formats for integration and combination of data drawn from diverse sources, where the original Web mainly concentrated on the interchange of documents. It is also about language for recording how the data relates to real world objects. That allows a person, or a machine, to start off in one database, and then move through an unending set of databases which are connected not by wires but by being about the same thing."(From http://www.w3.org/2001/sw/, italics added)
The paragraph above characterizes in a very high-level fashion how Semantic Web technologies are supposed to provide a path towards web-wide interoperability. Clearly, getting data to be couched in standard formats and allowing the relationship of data to the “real world” to be represented in a precise fashion are necessary conditions for turning “data” into machine-processable information having an invariant meaning across platforms (and to humans). However, we have italicised the phrase “move through” in the last sentence of the quotation to direct attention to the fact that when machines “move through” the semantic web they will typically be processing the information they encounter in some way. Thus, another aspect of the drive towards web-wide interoperability is the challenge of representing the processing that machines perform in a way that is invariant across platforms. The goal of this working group is to provide such representational formats for processes based on the use of rules and rule-based systems.
As can be seen by studying the use-cases presented in this document, rules are used to perform a wide variety of tasks, and, therefore, rule-based systems are not monolithic. Rules have been used to perform or validate inference, perform calculations, direct the flow of information, enforce integrity constraints on databases, represent and enforce policies, control devices and processes in real-time, determine the need for human intervention, and so on.
In light of this diversity the working group expects that RIF, rather than being a single all-encompassing format, will consist of several dialects, each dialect serving a particular set of related rule languages. The key idea is to attain the goal of interoperability (via interchange of RIF rules) within each dialect. This should allow the main benefits of RIF to be realized. For example, the invariant meaning of a set of integrity-constraint-enforcing rules would be represented within the appropriate RIF dialect and could then be translated into the native format of any of the formalisms capable of representing such rules.
Each RIF dialect will be built upon the same common core. RIF must be designed in such a way that it is possible to create new dialects based upon the core, as well as update existing dialects (upwardly compatible). This is in keeping with the working group charter’s call for an “extensible format.” Other requirements on the core, and RIF as a whole, are included in this document in the section Requirements. Work on the technical specification of RIF core is presented in the document Core.
Achieving inter-dialect interoperability is, by its very nature, an ill-constrained problem since, by definition, 100% meaning-preserving translations between dialects with different semantics are not likely to exist in most cases. That is not to say that useful inter-dialect “translation” is impossible, only that additional criteria are required in order to formulate precise notions of what satisfactory translation (via interchange of RIF rules) amounts to in such cases. Developing criteria for understanding and managing RIF inter-dialect translations is not within the current phase of RIF working group activity.