29212181
Concurrency and inheritance in actor-based object-oriented languages
Abstract The combination of concurrent and object-oriented programming is a promising paradigm. However, the design of such an integrated language faces a serious problem: concurrent features of the language may interfere with object-oriented features such as inheritance and encapsulation. We present a new concurrency control mechanism for concurrent object-oriented languages based on the actor model, with the aim of avoiding such a problem. The concurrency constraints of an object are expressed with a pair of constructs—behavior abstraction sets and replacement clauses. They are completely separated from the code of methods; moreover, they are the units of inheritance. We introduce a new replacement scheme called lazy replacement for actor-based languages to reduce complexity in expressing the concurrency constraints of objects. We examine the relationship between the proposed concurrency control mechanism and a well-known inheritance mechanism using an experimental language.
3145493
KPSP: A Knowledge Programming System based on Prolog
27932771
Novel algorithms for multicast communication in self-routing MIN-based ATM switches
We discuss the multicast communication in the self-routing multistage interconnection network (MIN) for constructing the internal architecture of asynchronous transfer mode (ATM) switches. Many applications of ATM switches require multicast communications in addition to conventional point-to-point communications. This paper presents a novel approach to supporting multicast communication, on the basis of the recursive scheme that recycles a multicast packet one or more times through the network to reach at desired destinations. We also propose cost-effective multicast algorithms providing deadlock-freedom in MIN-based ATM switches. The proposed algorithms require a small and fixed number of recycling passes and a reasonable number of links used. The proposed algorithms can be easily applicable to buffered MIN-based ATM switches.
39501622
A logic programming approach to hybrid knowledge representation
A new hybrid system called Sphinx is presented which combines classification-based reasoning with logic programming technique. It consists of two major components: a terminological component and an assertional one. The former uses a frame-based knowledge representation scheme based on classification and the latter is a theorem prover based on Horn logic. The assertional component can also handle a first-order query language and wh-questions. A new knowledge base maintenance mechanism based on the negation as failure inference rule enables Sphinx to support incremental assertions and retractions. In addition, Sphinx provides explanation capability to help the user in developing and debugging knowledge bases.
32944410
SPHINX - A Hybrid Knowledge Representation System
46360239
A New Algorithm for Subsumption Test
5763081
A probabilistic approach to metasearching with adaptive probing
An ever-increasing amount of valuable information is stored in Web databases, "hidden" behind search interfaces. To save the user's effort in manually exploring each database, metasearchers automatically select the most relevant databases to a user's query. In this paper, we focus on one of the technical challenges in metasearching, namely database selection. Past research uses a precollected summary of each database to estimate its "relevancy" to the query, and in many cases make incorrect database selection. In this paper, we propose two techniques: probabilistic relevancy modelling and adaptive probing. First, we model the relevancy of each database to a given query as a probabilistic distribution, derived by sampling that database. Using the probabilistic model, the user can explicitly specify a desired level of certainty for database selection. The adaptive probing technique decides which and how many databases to contact in order to satisfy the user's requirement. Our experiments on real hidden-Web databases indicate that our approach significantly improves the accuracy of database selection at the cost of a small number of database probing.
10280309
Analysis of User Web Traffic with A Focus on Search Activities
Although search engines are playing an increasingly important role in users’ Web access, our understanding is still limited regarding the magnitude of search-engine influence. For example, how many times do people start browsing the Web from a search engine? How much percentage of Web traffic is incurred as a result of search? To what extent does a search engine like Google extend the scope of Websites that users can reach? To study these issues, in this paper we analyze a real Web access trace collected over a period of two and half months from the UCLA Computer Science Department. Our study indicates that search engines influence about 13.6% of the users’ Web traffic directly and indirectly. In addition, our study provides realistic estimates for certain key parameters used for Web modelling.
9811102
Four-bend top-down global routing
We propose a new global net distribution approach for high-performance m/spl times/m two-dimensional arrays of very large scale integration and multichip-modules. The objective is to route n nets with minimum density of global cells, using a "small" number of bends. There are a number of applications where it is necessary to limit the number of bends on each wire. For example, it is desirable to limit the number of bends on each microstrip (transmission) line, for mismatches of line impedance can cause reflections from the junction points such as bends and vias. Furthermore, for high-performance routing, intersections of wires cause the use of more vias, which in turn require the use of more routing resources (because of the larger via pitch). This is the first paper that addresses a graph-theoretic framework to solve the bend-constrained global routing problem in two-dimensional arrays. In this paper, at each level of an underlying quad-tree, we present a novel four-bend routing algorithm by decomposing the original problem at level i into two subproblems that can be solved exactly based on a two-stage approach of smaller-sized linear program followed by min-cost flow networks. The overall (i.e., entire level of the four-way partition hierarchy) constraint and variable size for the first stage is O(md/sub o/), while the overall run time for the second stage is O(n/sup 3/ log n/sup 2/). The time complexity of such a hierarchical approach is one order of magnitude less than one of constructing a global routing using the min-cost-flow-based flat design approach. Last, we present an extension that permits a limited degree of control over the number of bends. The proposed algorithm can also be used for estimating the wireability in the early design planning stage for high-level synthesis. Experimental results showed the effectiveness of the proposed algorithm.
2800780
Page quality: in search of an unbiased web ranking
In a number of recent studies [4, 8] researchers have found that because search engines repeatedly return currently popular pages at the top of search results, popular pages tend to get even more popular, while unpopular pages get ignored by an average user. This "rich-get-richer" phenomenon is particularly problematic for new and high-quality pages because they may never get a chance to get users' attention, decreasing the overall quality of search results in the long run. In this paper, we propose a new ranking function, called page quality that can alleviate the problem of popularity-based ranking. We first present a formal framework to study the search engine bias by discussing what is an "ideal" way to measure the intrinsic quality of a page. We then compare how PageRank, the current ranking metric used by major search engines, differs from this ideal quality metric. This framework will help us investigate the search engine bias in more concrete terms and provide clear understanding why PageRank is effective in many cases and exactly when it is problematic. We then propose a practical way to estimate the intrinsic page quality to avoid the inherent bias of PageRank. We derive our proposed quality estimator through a careful analysis of a reasonable web user model, and we present experimental results that show the potential of our proposed estimator. We believe that our quality estimator has the potential to alleviate the rich-get-richer phenomenon and help new and high-quality pages get the attention that they deserve.
5658625
Finding replicated Web collections
Many web documents (such as JAVA FAQs) are being replicated on the Internet. Often entire document collections (such as hyperlinked Linux manuals) are being replicated many times. In this paper, we make the case for identifying replicated documents and collections to improve web crawlers, archivers, and ranking functions used in search engines. The paper describes how to efficiently identify replicated documents and hyperlinked document collections. The challenge is to identify these replicas from an input data set of several tens of millions of web pages and several hundreds of gigabytes of textual data. We also present two real-life case studies where we used replication information to improve a crawler and a search engine. We report these results for a data set of 25 million web pages (about 150 gigabytes of HTML data) crawled from the web.