Grzegorz J. Nalepa

FORMALIZATION AND MODELING OF RULES USING THE XTT2 METHOD

The paper discusses a new knowledge representation for rule-based systems called XTT2. It combines decision trees and decision tables forming a transparent and hierarchical visual representation of the decision units linked into a workflow-like structure. There are two levels of abstraction in the XTT2 model: the lower level, where a single knowledge component defined by a set of rules working in the same context is represented by a single decision table, and the higher level, where the structure of the whole knowledge base is considered. This model has a concise formalization which opens up possibility of well-defined, structured design and verification of formal characteristics. Based on the visual XTT2 model, a textual representation of the rule base is generated. A dedicated engine provides a unified run-time environment for the XTT2 rule bases. The focus of the paper is on the formalization of the presented approach. It is based on the so-called ALSV(FD) logic that provides an expressive calculus for rules.

The HeKatE methodology. Hybrid engineering of intelligent systems

The HeKatE methodology. Hybrid engineering of intelligent systems This paper describes a new approach, the HeKatE methodology, to the design and development of complex rule-based systems for control and decision support. The main paradigm for rule representation, namely, eXtended Tabular Trees (XTT), ensures high density and transparency of visual knowledge representation. Contrary to traditional, flat rule-based systems, the XTT approach is focused on groups of similar rules rather than on single rules. Such groups form decision tables which are connected into a network for inference. Efficient inference is assured as only the rules necessary for achieving the goal, identified by the context of inference and partial order among tables, are fired. In the paper a new version of the language—XTT22—is presented. It is based on ALSV(FD) logic, also described in the paper. Another distinctive feature of the presented approach is a top-down design methodology based on successive refinement of the project. It starts with Attribute Relationship Diagram (ARD) development. Such a diagram represents relationships between system variables. Based on the ARD scheme, XTT tables and links between them are generated. The tables are filled with expert-provided constraints on values of the attributes. The code for rule representation is generated in a humanreadable representation called HMR and interpreted with a provided inference engine called HeaRT. A set of software tools supporting the visual design and development stages is described in brief.

A study of methodological issues in design and development of rule-based systems: proposal of a new approach

Rule‐based systems (RBSs) constitute a powerful technology for declarative encoding and automated processing of large bodies of knowledge. A typical RBS consists of a knowledge base containing facts and production rules, and an inference engine managing the reasoning process. Despite their simple conceptual scheme, design and development of a RBS often turn out to be unexpectedly complex task. This paper presents an overview of issues concerning design and development of such systems. Differences between RBSs and classical software are exemplified, and design and implementation issues are analyzed. A novel, consistent, three‐phase methodology incorporating conceptual, logical, and physical design is outlined. Moreover, tools supporting the complete design and development process are presented.

Architecture of the HeaRT hybrid rule engine

In this paper a new rule engine called HeaRT (HeKatE Run Time) is proposed. It uses a custom rule representation called XTT2, which is based on a formalized rule description and allows a formalized analysis of rule quality. The engine is integrated with a complete design environment that provides visual rule design capabilities. The engine supports modularized rule bases and custom inference mechanisms. The rule-based logic can be integrated with the environment using external callback functions in Prolog and Java. In the paper the architecture of the engine is discussed as well as selected implementation issues are given.

HalVA - rule analysis framework for XTT2 rules

Quality and reliability issues are important in development and exploration of rule-based systems. In the paper a formalized knowledge representation for rules called XTT2 is considered. It is a rule language based on an expressive attribute logic called ALSV(FD). A custom runtime and verification framework for XTT2 called HalVA is proposed. It allows for verification of certain formal properties of rules, including determinism, subsumption or completeness.

Algorithms for rule inference in modularized rule bases

In the paper an extended knowledge representation for rules is considered. It is called Extended Tabular Trees (XTT2) and it provides a network of decision units grouping rules working in the same context. The units are linked into an inference network, where a number of inference options are considered. The original contribution of the paper is the proposal and formalization of several different inference algorithms working on the same rule base. Such an approach allows for a more flexible rule design and deployment, since the same knowledge base may be used in different ways, depending on the application.

Enriching business processes with rules using the oryx BPMN editor

BPMN is a leading visual notation for modeling Business Processes. Although it can be efficiently used for modeling workflow structures, it is not suitable for modeling the low-level logic of particular tasks in the process. Recently, Business Rules have been used for this purpose. Such rules are often specified in natural language and in an informal way. In this paper, we consider an approach to the integration of Business Processes with Business Rules. As a proof of concept, we propose a framework based on the Oryx BPMN editor integrated with rule-based tools. The goal of the integration of the BPMN editor with the XTT2 rule framework is to provide an environment for visual modeling processes with formally described business rules. We also discuss execution options of the integrated model. In the future, this opens up a possibility to execute such models using the HeaRT rule engine.

UML REPRESENTATION FOR RULE-BASED APPLICATION MODELS WITH XTT2-BASED BUSINESS RULES

In this paper challenges of using Knowledge Engineering methods in the Software Engineering practice, with focus on the visual design methods for software applications, are discussed. The paper concerns practical design issues of rule-based models integrated with business applications built using the Model-View-Controller (MVC), or equivalent architectural pattern. The Unified Modeling Language (UML) constitutes a standardized notation among software engineers. Various attempts has been made to design the model in a way alternative to UML. Recently, the Business Rules approach has been proposed as a new way of capturing the functional requirements in a designer-friendly fashion. However, concepts on which the rule-based representation is based cannot be directly modeled in UML, because the semantics of UML diagrams does not correspond to rule semantics. Our research considers a method of designing rule bases which will be proper and consistent with the UML design. The approach has several important features: the core logic of the application is clearly identified and separated, and it is built in a declarative way, which makes the design transparent, easier to follow and develop. When rules are used to model the application logic, one has to keep in mind some common and well-known limitations of the existing rule tools. Our solution to these problems consists of using an expressive visual rule design formalism called XTT2, defining a direct translation between XTT2 and selected UML diagrams, implementing practical translators between the logical model and MOF-based UML model, and using the verification features provided with the XTT2 framework to assure the quality of the rule base. This solution seems to be superior both to existing visual UML rule notations, as well as visual design tools for rules. It does not extend any custom UML artifacts and can be used with standard UML tools.

Designing reliable web security systems using rule-based systems approach

This paper shows that rule-based web security systems, such as firewalls, can be largely improved by using formal design and verification techniques. The principal idea consists of an integrated design and verification methodology, supported by an integrated graphical environment for rule-based systems development. System structure is described in a XML-based meta-level knowledge representation language. System domain knowledge and semantics is represented in RDF and Ontologies-based description. Formal properties of the system can be verified on-line by an integrated Prolog-based inference engine.

Proposal of Formal Verification of Selected BPMN Models with Alvis Modeling Language

BPMN is a leading visual notation for modeling business processes. Although there is many tools that allows for modeling using BPMN, they mostly do not support formal verification of models. The Alvis language was developed for modeling and verification of embedded systems. However, it is suitable for the modeling of any information systems with parallel subsystems. The goal of this paper is to describe the concept of using Alvis for a formal verification of selected BPMNmodels. In the paper a translation from BPMN to Alvis model is proposed. The translation is discussed and evaluated using a simple yet illustrative example.