Benjamin N. Grosof

Itinerant agents for mobile computing

Describes a framework for itinerant agents that can be used to implement secure, remote applications in large, public networks such as the Internet or the IBM Global Network. Itinerant agents are programs, dispatched from a source computer, that roam among a set of networked servers until they accomplish their task. This is an extension to the client/server model in which the client sends a portion of itself to the server for execution. An additional feature of itinerant agents is their ability to migrate from server to server, perhaps seeking one that can help with the users task or perhaps collecting information from all of them. A major focus of the article is the agent meeting point, an abstraction that supports the interaction of agents with each other and server based resources The article begins with an overview of the operation of an itinerant agent framework and a review of previous work. The authors consider likely applications of itinerant agents and discuss one specific example in detail. They give an architectural description of the structure of itinerant agents, the languages employed to create them, and the execution environments required at the servers; and also a detailed description of how an itinerant agent is processed at a server. Security issues are then discussed and finally they consider the technical advantages of the itinerant agent framework and the services it enables. >

A declarative approach to business rules in contracts: courteous logic programs in XML

We address why, and especially how, to represent business rules in e-commerce contracts. By contracts, we mean descriptions of goods and services offered or sought, including ancillary agreements detailing terms of a deal. We observe that rules are useful in contracts to represent conditional relationships, e.g., in terms& conditions, service provisions, and surrounding business processes, and we illustrate this point with several examples. We analyze requirements (desiderata) for representing such rules in contracts. The requirements include: declarative semantics so as to enable shared understanding and interoperability; prioritized conflict handling so as to enable modular updating/revision; ease of parsing; integration into WWW-world software engineering; direct executability; and computational tractability. We give a representational approach that consists of two novel aspects. First, we give a new fundamental knowledge representation formalism: a generalized version of Courteous Logic Programs (CLP), which expressively extends declarative ordinary logic programs (OLP) to include prioritized conflict handling, thus enabling modularity in specifying and revising rule-sets. Our approach to implementing CLP is a courteous compiler that transforms any CLP into a semantically equivalent OLP with moderate, tractable computational overhead. Second, we give a new XML encoding of CLP, called Business Rules Markup Language (BRML), suitable for interchange between heterogeneous commercial rule languages. BRML can also express a broad subset of ANSI-draft Knowledge Interchange Format (KIF) which overlaps with CLP. Our new approach, unlike previous approaches, provides not only declarative semantics but also prioritized conflict handling, ease of parsing, and integration into WWW-world software engineering. We argue that this new approach meets the overall requirements to a greater extent than any of the previous approaches, including than KIF, the leading previous declarative approach. We have implemented both aspects of our approach; a free alpha prototype called Common-Rules was released on the Web in July of 1999, at http://alphaworks.ibm.com.

A logic-based knowledge representation for authorization with delegation

We introduce Delegation Logic (DL), a logic-based knowledge representation (i.e., language) that deals with authorization in large-scale, open distributed systems. Of central importance in any system for deciding whether requests should be authorized in such a system are delegation of authority, negation of authority, and conflicts between authorities. DLs approach to these issues and to the interplay among them borrows from previous work on delegation and trust management in the computer security literature and previous work on negation and conflict handling in the logic programming and nonmonotonic reasoning literature, but it departs from previous work in some crucial ways. We present the syntax and semantics of DL and explain our novel design choices. We focus on delegation, including explicit treatment of delegation depth and delegation to complex principles. Compared to previous logic-based approaches to authorization, DL provides a novel combination of features: it is based on logic programs, expresses delegation depth explicitly, and supports a wide variety of complex principles (including but not limited to k-out-of-n thresholds). Compared to previous approaches to trust management, DL provides another novel feature: a concept of proof-of-compliance that is not entirely ad-hoc and that is based on model theoretic semantics (just as usual logic programs have a model-theoretic semantics).

SweetDeal: representing agent contracts with exceptions using XML rules, ontologies, and process descriptions

SweetDeal is a rule-based approach to representation of business contracts that enables software agents to create, evaluate, negotiate, and execute contracts with substantial automation and modularity. It builds upon the situated courteous logic programs knowledge representation in RuleML, the emerging standard for Semantic Web XML rules. Here, we newly extend the SweetDeal approach by also incorporating process knowledge descriptions whose ontologies are represented in DAML+OIL (emerging standard for Semantic Web ontologies) thereby enabling more complex contracts with behavioral provisions, especially for handling exception conditions (e.g., late delivery or non-payment) that might arise during the execution of the contract. This provides a foundation for representing and automating deals about services -- in particular, about Web Services, so as to help search, select, and compose them. Our system is also the first to combine emerging Semantic Web standards for knowledge representation of rules (RuleML) with ontologies (DAML+OIL) for a practical e-business application domain, and further to do so with process knowledge. This also newly fleshes out the evolving concept of Semantic Web Services. A prototype (soon public) is running.

An Approach to Using XML and a Rule-Based Content Language with an Agent Communication Language

We argue for an XML encoding of FIPA Agent Communication Language (ACL), and give an alpha version of it, called Agent Communication Markup Language (ACML), which we have implemented. The XML approach facilitates: (a) developing/maintaining parsers, integrating with WWW-world software engineering, and (b) the enriching capability to (hyper-)link to ontologies and other extra information. The XML approach applies similarly to KQML as well. Motivated by the importance of the content language aspect of agent communication, we focus in particular on business rules as a form of content that is important in e-commerce applications such as bidding negotiations. A leading candidate content language for business rules is Knowledge Interchange Format (KIF), which is currently in the ANSI standards committee process. We observe several major practical shortcomings of KIF as a content language for business rules in e-commerce. We argue instead for a knowledge representation (KR) approach based on Courteous Logic Programs (CLP) that overcomes several of KIF’s representational limitations, and argue for this CLP approach, e.g., for its logical non-monotonicity and its computational practicality. CLP is a previous KR that expressively extends declarative ordinary logic programs cf. Prolog; it includes negation-as-failure plus prioritized conflict handling. We argue for an XML encoding of business rules content, and give an alpha version of it, called Business Rules Markup Language (BRML), which we have implemented. BRML can express both CLP and a subset of KIF (i.e., of first-order logic) that overlaps with CLP. BRML expressively both extends and complements KIF. The overall advantages of an XML approach to content language are similar to those for the XML approach to ACL, and indeed complements the latter since content is carried within ACL messages. We have implemented both ACML and BRML/CLP; a free alpha prototype of BRML/CLP, called IBM CommonRules, was released on the Web in July of 1999.

Dynamics of an Information-Filtering Economy

Our overall goal is to characterize and understand the dynamic behavior of information economies: very large open economies of automated information agents that are likely to come into existence on the Internet. Here we model a simple information-filtering economy in which broker agents sell selected articles to a subscribed set of consumers. Analysis and simulation of this model reveal the existence of both desirable and undesirable phenomena, and give some insight into their nature and the conditions under which they occur. In particular, efficient self-organization of the broker population into specialized niches can occur when communication and processing costs are neither too high nor too low, but endless price wars can undermine this desirable state of affairs.

SweetDeal: Representing Agent Contracts with Exceptions Using Semantic Web Rules, Ontologies, and Process Descriptions

This paper addresses the problem of how to represent exception-handling provisions in automated knowledge-based e-contracts. In many natural language contracts, such provisions constitute the majority of the contract volume. The paper makes three novel contributions. (1) The rule-based SweetDeal e-contracting approach is extended to incorporate ontology knowledge (specifically, ontologies about business processes), and an application scenario about late delivery in manufacturing supply-chain management shows how it can be used to represent provisions for exception-handling. The contract rules are represented in the Situated Courteous Logic Programs knowledge representation encoded in RuleML, the leading approach to Semantic Web rules. The process ontologies are represented in description logic encoded in DAML+OIL, close predecessor of W3Cs OWL, the leading approach to semantic Web ontologies. This system is the first to combine these emerging semantic Web standards with one another and for a practical e-business application domain. (2) A simple new technical mechanism for the semantic Web is presented that integrates ontology knowledge with rule knowledge: Rule predicates are defined by reference to ontological classes or properties. (3) Process ontology knowledge drawn from the MIT Process Handbook, a large repository used by practical industrial process designers, is represented in DAML+OIL/OWL, and some of this knowledge is formalized and used for the e-contracting application scenario. Stated more generally, the approach in this paper provides a foundation for representing and automating deals about services--in particular, for helping to search, select, and compose semantic Web services.

Logic Programming with Defaults and Argumentation Theories

We define logic programs with defaults and argumentation theories, a new framework that unifies most of the earlier proposals for defeasible reasoning in logic programming. We present a model-theoretic semantics and study its reducibility and well-behavior properties. We use the framework as an elegant and flexible foundation to extend and improve upon Generalized Courteous Logic Programs (GCLP) [19]--one of the popular forms of defeasible reasoning. The extensions include higher-order and object-oriented features of Hilog and F-Logic [7,21]. The improvements include much simpler, incremental reasoning algorithms and more intuitive behavior. The framework and its Courteous family instantiation were implemented as an extension to the FLORA-2 system.

Automated negotiation from declarative contract descriptions

Our approach for automating the negotiation of business contracts proceeds in three broad steps. First, determine the structure of the negotiation process byapplying general knowledge about auctions and domain-specific knowledge about the contract subject along with preferences from potential buyers and sellers. Second, translate the determined negotiation structure into an operational specification for an auction platform. Third, map the negotiation results to a final contract. We have implemented a prototype which supports these steps, employing a declarative specification (in Courteous Logic Programs) of (1) high-level knowledge about alternative negotiation structures, (2) general-case rules about auction parameters, (3) rules to map the auction parameters to a specific auction platform, and (4) special-case rules for subject domains. We demonstrate the flexibility of this approach by automatically generating several alternative negotiation structures for a previous domain: travel-shopping in a trading agent competition.

Non-monotonicity in probabilistic reasoning

We start by defining an approach to non-monotonic probabilistic reasoning in terms of non-monotonic categorical reasoning. We identify a type of non-monotonic probabilistic reasoning, akin to default inheritance, that seems to be commonly found in practice. We formulate this in terms of the Maximization of Conditional Independence (MCI), and identify a variety of applications for this sort of default. We propose a formalization using Point-wise Circumscription. We compare MCI to Maximum Entropy, another kind of non-monotonic principle, and conclude by raising a. number of open questions.