NetWeaver Developer

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NetWeaver Developer is a knowledgebase development system. This article

Contents

  1. gives a brief history of the system,
  2. summarizes key features of the software,
  3. is a bit of a primer, describing basic attributes of a NetWeaver knowledgebase, and
  4. provides secondary references that independently document some of the NetWeaver applications developed since the late 1980s (see the #References section in this article, as well as applications documented for the EMDS system).

First, though, a word about knowledgebases. While there are various ways of describing a knowledgebase, perhaps one of the more central concepts is that a knowledgebase provides a formal specification for interpreting information. [1] Formal in this context means that the specification is ontologically committed [2] to the semantics and syntax prescribed by a knowledgebase processor (aka, an engine).

A brief history

NetWeaver was created in late 1991 as a response to ease knowledge engineering tasks by giving a graphical user interface to the ICKEE (IConic Knowledge Engineering Environment) inference engine developed at Penn State University by Bruce J. Miller and Michael C. Saunders. The first iterations were simply a visual representation of dependency networks stored in a LISP-like syntax. NetWeaver quickly evolved into an interactive interface where the visual environment was also capable of editing the dependency networks and saving them in the ICKEE file format. Eventually NetWeaver became "live" in the sense that it could evaluate the dependency networks in real time.

NetWeaver basics

A NetWeaver knowledgebase graphically represents a problem to be evaluated as networks of topics, each of which evaluates a proposition. The formal specification of each topic is graphically constructed, and composed of other topics (e.g., premises) related by logic operators such as and, or, not, etc. NetWeaver topics and operators return a continuous-valued ‘‘truth value’’, [3] that expresses the strength of evidence that the operator and its arguments provide to a topic or to another logic operator. The specification of an individual NetWeaver topic supports potentially complex reasoning because both topics and logic operators may be specified as arguments to an operator. Considered in its entirety, the complete knowledgebase specification for a problem can be thought of a mental map of the logical dependencies among propositions. In other words, the knowledgebase amounts to a formal logical argument in the classical sense. [4]

When logic meets graphics

Cognitive theory suggests that human beings have two fundamental modes of reasoning: logical (albeit however informally some folks may do that when left to their own devices) and spatial. [5] Interesting things happen when logic is implemented graphically.

First, the knowledge of individual subject-matter experts engaged in [[knowledge engineering]] often is not fully integrated when dealing with complex problems, at least initially. Rather, this knowledge may exist in a somewhat more loosely organized state, a sort of knowledge soup with chunks of knowledge floating about in it. A common observation of knowledge engineers experienced in graphically designing knowledgebases is that the process of constructing a graphic representation of problem-solving knowledge in a formal logical framework seems to be synergistic, with new insights into the expert's knowledge emerging as the process unfolds. (At the moment, this assertion is largely anecdotal. Contributors to this article need to find a suitable way to document this point, because it is actually a rather important finding not simply limited to NetWeaver, but knowledge engineering more broadly).

Second, synergies similar to those observed in organizing the reasoning of individual subject-matter experts also can occur in knowledge engineering projects that require the interaction of multiple disciplines. For example, many different kinds of specialists may be involved in evaluating the overall health of a watershed. Use of a formal logic system, with well defined syntax and semantics, allows specialists’ representation of their problem solving approach to be expressed in a common language, which in turn facilitates understanding of how all the various perspectives of the different specialists fit together.

About NetWeaver knowledgebases

A NetWeaver knowledgebase has been defined by the developers as a network of networks (Miller and Saunders 2002). Each network corresponds to a topic of interest in the problem being evaluated by the knowledgebase.

NetWeaver knowledgebases are object-based. There are two basic types of objects: networks, and data links, each of which is represented in the logic structure by a programming object which has both state and behavior.

The NetWeaver engine is a Windows dynamic link library (DLL) developed by Rules of Thumb, Inc. (North East, PA). NetWeaver Developer is an interface to the engine that is used for designing knowledgebases.

Logic networks

A knowledgebase represents knowledge about how to solve a problem in terms of the topics of interest in the problem domain, and relations among these topics. Each logic network in a NetWeaver knowledge base represents a proposition about the condition of some ecosystem state or process.

A data link is an elementary dependency network with slightly modified behavior.

Truth values

The truth value is the basic state variable of networks and data links. It expresses an observation's degree of membership in a set. Evaluations of degree of set membership are quantified in the semantics of fuzzy logic. [6] [7] [8] [9] [10] Equivalently, think of the truth value metric as expressing the degree to which evidence supports the proposition of the network or data link; in EMDS, the symbology for maps displaying network truth values is based on the concept of strength of evidence. For additional discussion on this topic, see Interpretation of Truth Values.

Data links are frequently used to read a datum and evaluate its degree of membership in a concept that is quantified in a fuzzy argument (an argument that quantifies fuzzy set membership). Thus, in a data link the argument is a mathematical statement of a proposition. Some simple examples include:

Interpretation of truth values within networks must be treated more generally, because the truth value of a network may depend on several to many logic operators. Simple examples related to the two key logic operators, AND and OR, are:

relation, then the truth value of the operator is -1 (no support).

As with data links, networks may also evaluate to partially true. Two conditions give rise to this condition in NetWeaver:

Notes

  1. ↑ Walters, J.R., and N.R. Nielsen. 1988. Crafting Knowledge-based Systems. New York: John Wiley and Sons. 342 p.
  2. ↑ Gruber, T.R. 1995. Toward principles for the design of ontologies used for knowledge sharing. International Journal of Human-Computer Studies 43:907-928.
  3. ↑ Miller, B.J., and M.C. Saunders. 2002. The NetWeaver Reference Manual. University Park, PA: Pennsylvania State University. 61 p.
  4. ↑ Halpern, D.F. 1989. Thought and Knowledge, An Introduction to Critical Thinking. Hillsdale, NJ: Lawrence Erlbaum Associates. 517 p.
  5. ↑ Stillings, N.A., M.H. Feinstein, J.L. Garfield, [et al.]. 1991. Cognitive Science: An Introduction. Cambridge, MA: MIT Press. 533 p.
  6. ↑ Zadeh, L.A. 1965. Fuzzy sets. Information and Control 8:338-353.
  7. ↑ Zadeh, L. A. 1968. Probability measures of fuzzy events. J. Math. Anal. and Appl. 23:421-427.
  8. ↑ Zadeh, L.A. 1975. The concept of a linguistic variable and its application to approximate reasoning, part I. Information Science 8, 199-249.
  9. ↑ Zadeh, L. A. 1975b. The concept of a linguistic variable and its application to approximate reasoning. Part II. Information Science 8:301-357.
  10. ↑ Zadeh, L.A. 1976. The concept of a linguistic variable and its application to approximate reasoning. Part III. Information Science 9: 43-80.

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