Valentin's Blog

Last week I attended a one day introductory seminar by ILOG about their business rule management system (BRMS). I did it to get a better feel for the differences and similarities between these systems and logic programming (LP) /Semantic Web rule systems (SWR) - beyond the name and the idea to represent knowledge somehow as "if x then y" structures. So here's what I learned:

• [Please see update below] Atomic Rules: The biggest difference really is that rules in BRMS's do not interact automatically. If you have a LP or SWR system with the knowledge base: 
        Rule A: IF q(?A) THEN r(?A)
        Rule B: IF p(?A) THEN q(?A)
        p(x)
  and you ask the query r(?A) you get the answer ?A=x, a LP/SWR system will automatically realize that it has to apply first rule B and then rule A. A BRMS will evaluate the rules in isolation - rule B will fire but rule A will not. This is because rule A has no access to the results of rule B. A BRMS system can replicate the behavior of the LP/SWR rule base through the use of rule flows. A rule flow is a description of a sequence of rule sets that have to be applied. In the example above we could define that first rule B is applied and then rule A - but note that unlike in LP/SWR systems we have to do this manually. In real life you normally wouldn't specify single rules in rule flows, rather something like: apply first syntactic input check rules, then apply rules to create credit rating, then find appropriate department to route document to etc.
  It easy to say that LP/SWR systems are superior because of their more powerful formalisms, but remember the downside to that: they are harder to understand and implement, slower to evaluate and harder to debug. There is also a certain beauty to having procedural problem solving knowledge explicitly represented and not hidden in rules. I'm hesitant to claim that a BRMS would become better by using a more powerful SWR system, probably, but it would require hard work on the user interfaces.  
• Multi Paradigm: The textbook way to use a BRMS seems to be to start with a business process and to externalize complex decision points from that into decision services that are realized with rules organized in rule flows. And the rules in the rule flow can easily access other programs, webservices and objects. Hence rules are embedded in a multi-paradigm context and restricted to only the subset of tasks they are good at - much more so than in the usual discussion of LP/SWR systems.
• Maintenance vs. sharing:  The main advantage of BRMS's used in the ILOG marketing material seems the ease of maintenance - the assumption that business logic made explicit in rules is easier and cheaper to adapt and maintain. So far there seems to be relatively little interest in sharing or selling these rules. This stands in contrast to the SWR developments that focus on sharing.
• Semantics: Well, a formal semantic is a central topic for the LP and even more for the SWR community, in contrast the BRMS people seem to be not too concerned with that and just utilize some kind of simplified forward chaining.

And the ILOG system is quite a bit more mature than any LP or SWR system I know - but then, that is to be expected from a relatively large company that has been building these systems for years.

Update: I've removed the entire first part of this post - It represents what the ILog presenter person said, however, upon reading a bit more I realized that it just isn't true: ILog (like other BRMS manufacturers) is quite proud of their Rete based forward chaining inference engine. So, that's still a different approach (forward chaining vs. declarative semantics + different inference algorithms in the SW world) but not as different as I initially claimed. Sorry.

Labels: SemanticWeb

The Semantic Web, by whatever name it comes to be called, is inevitable.

This is Michael K. Bergman statement in the article "Structure Paves the Way to the Semantic Web".  And I'm only using his statement as an easily accessible example here - similar statements have been repeated thousands of times. So - is this so? Is the Semantic Web inevitable?

Well,  its easy to be certain, if only you are sufficiently vague. In general people making this statement do not give a definition for the Semantic Web - Michael K. Bergman being no exception. This way they can generalize the term until its almost without meaning and are not really making any prediction(s). Humankind is going to continue to develop better tools to organize information and these tools will be somehow grow on/out of the current Internet? Well, duh, I'm not going to argue with that.

But: isn't it part of the Semantic Web vision that this will be achieved by publishing machine understandable data in a distributed fashion similar to the current WWW? Still a very vague statement, but one that allows for alternative visions: we could also see better information organization based on natural language processing technologies or on a centralized everything-is-stored-at-Google model. So, no; this Semantic Web seems likely, but is not inevitable.

And the traditional uppercase Semantic Web vision even states that this will be achieved by building one distributed global knowledge based systems (kbs) based on traditional knowledge representation techniques - by far eclipsing all previous kbs's in scale and diversity of content. Stated this way the only thing inevitable about the Semantic Web is its failure.

So then, is the Semantic Web inevitable? Depends, please define Semantic Web ;)

Labels: SemanticWeb

In this paper we describe novel ideas and their prototypical implementation for the visualization of rule bases. In the creation of the visualization our approach considers not only the structure of a rule base but also records of its usage. We also discuss methods to address the challenges for visualization tools posed by rule bases that are large, created with high level knowledge acquisition tools or that contain low level rules that should remain hidden from the users.

My paper for the special track on knowledge visualization of the I-Know conference this fall. The entire paper is here. Its no rocket science, but I really think its something that's generally useful (for relatively small rule bases) and that hasn't been done before.

Labels: KBSDevelopment, publication

In a recent IEEE Intelligent Systems John F. Sowa wrote an interesting article that should be read be people interested in the logical side of the Semantic Web. Two of the quotes I particularly liked:

[...] computational complexity is important. But complexity is a property of algorithms, and only indirectly a property of problems, since most problems can be solved by different algorithms with different complexity. The language in which a problem is stated has no effect on complexity. Reducing the expressive power of a logic does not solve any problems faster; its only effect is to make some problems impossible to state.

and on Language and Logic:

What makes formal logic hard to use is its rigidity and its limited set of operators. Natural languages are richer, more expressive, and much more flexible. That flexibility permits vagueness, which some logicians consider a serious flaw, but a precise statement on any topic is impossible until all the details are determined. As a result, formal logic can only express the final result of a lengthy process of analysis and design. Natural language, however, can express every step from the earliest hunch or tentative suggestion to the finished specification.

In short, there are two equal and opposite fallacies about language and logic:  at one extreme, logic is unnatural and irrelevant; at the opposite extreme, language is incurably vague. A more balanced view must recognize the virtues of both:  logic is the basis for precise reasoning in every natural language; but without vagueness in the early stages of a project, it would be impossible to explore all the design options.

The entire article is available for free as a "preprint" here.

Labels: AI, SemanticWeb

Last week I was at the SEKE (Nineteenth International Conference on Software Engineering and Knowledge Engineering) to present some of my work on the debugging of rule based system. Not much to report - decent conference, heard nothing that was excitingly new, met some nice people and the conference hotel had a great view on Boston's skyline - see below (the only real reason for this post - it's been a while since I last posted one of my pictures)

Labels: pictures

(Please excuse the German)

Bisher gibt es kein integriertes Werkzeug, welches sowohl die kollaborative Erstellung eines Indexes relevanter Internetressourcen („Social Bookmarking“) als auch einer gemeinsamen Ontologie, welche zur Organisation des Indexes genutzt wird, integriert unterstützt. Die derzeitigen Werkzeuge gestatten entweder die Erstellung einer Ontologie oder die Strukturierung von Ressourcen entsprechend einer vorgegebenen, unveränderlichen Ontologie bzw. ganz ohne jegliche Struktur. In dieser Arbeit zeigen wir, wie sich kollaboratives Tagging und kollaborative Ontologieentwicklung vereinen lassen, so dass jeweilige Schwächen vermieden werden und die Stärken einander ergänzen. Wir präsentieren SOBOLEO, ein System, das kollaborativ und web-basiert die Erstellung, Erweiterung und Pflege von Taxonomien und gemeinsamer Lesezeichensammlung ermöglicht und gleichzeitig die Annotierung von Internetressourcen mit Konzepten aus der erstellten Taxonomie unterstützt.

For once a German publication (this may be my first) about the relations between tagging and semantic annotations (and Soboleo). Its written by the usual people (Simone Braun, Andreas Schmidt and me) and will presented at the German Mensch und Computer conference by Simone.

It focusses on the question why you could want to augment tags with more structure. You can access the entire paper here.

Labels: publication, SOBOLEO

Some of the more notable links from the past weeks:

Google and the deep web - Great blog post summarizing and collecting links about Google's strategies in dealing with the deep web.

People-Powered Search - Article about the newly emerging sites that directly harness human participation to improve search.

How GPUs work - nice introductory piece into the structure of modern Graphics cards. This is for you, if you (like me) believe that GPU are starting to play a larger role in general purpose computing but have no clou how they work internally.

Don't Stand So Close To Me - Social conventions in Second Life. About how much Avatars act like humans in real life.

Second Earth - Long Technology Review about the idea of the "mirror world" (think the combination of SecondLife of Google Earth). You may need to register at technology review - but its an elaborate 11page article, so its worth the hassle.

A video about Spore - Will Wright's (the inventor of SimCity and the Sims) newest project that looks like it can change all ours perceptions what computer games can be and how suitable computer tools can really expand a humans potential (you'll understand me after you watched the video).

And on the funny side of things: Folksonomy is the most hated Internet word and two funny videos about PowerPoint.

As usual you can find all the links at del.icio.us, the newest ones are also always shown in the sidebar of this blog.

Labels: links