In this paper, we analyze the efficiency of Monte Carlo methods for incremental computation of PageRank, personalized PageRank, and similar random walk based methods (with focus on SALSA), on large-scale dynamically evolving social networks. We assume that the graph of friendships is stored in distributed shared memory, as is the case for large social networks such as Twitter. For global PageRank, we assume that the social network has n nodes, and m adversarially chosen edges arrive in a random order. We show that with a reset probability of ε, the expected total work needed to maintain an accurate estimate (using the Monte Carlo method) of the PageRank of every node at all times is [EQUATION]. This is significantly better than all known bounds for incremental PageRank. For instance, if we naively recompute the PageRanks as each edge arrives, the simple power iteration method needs [EQUATION] total time and the Monte Carlo method needs O ( mn /ε) total time; both are prohibitively expensive. We also show that we can handle deletions equally efficiently. We then study the computation of the top k personalized PageRanks starting from a seed node, assuming that personalized PageRanks follow a power-law with exponent α < 1. We show that if we store R > q ln n random walks starting from every node for large enough constant q (using the approach outlined for global PageRank), then the expected number of calls made to the distributed social network database is O ( k /( R (1-α)/α )). We also present experimental results from the social networking site, Twitter, verifying our assumptions and analyses. The overall result is that this algorithm is fast enough for real-time queries over a dynamic social network.

Abstract In this paper we report research results investigating microblogging as a form of electronic word‐of‐mouth for sharing consumer opinions concerning brands. We analyzed more than 150,000 microblog postings containing branding comments, sentiments, and opinions. We investigated the overall structure of these microblog postings, the types of expressions, and the movement in positive or negative sentiment. We compared automated methods of classifying sentiment in these microblogs with manual coding. Using a case study approach, we analyzed the range, frequency, timing, and content of tweets in a corporate account. Our research findings show that 19% of microblogs contain mention of a brand. Of the branding microblogs, nearly 20% contained some expression of brand sentiments. Of these, more than 50% were positive and 33% were critical of the company or product. Our comparison of automated and manual coding showed no significant differences between the two approaches. In analyzing microblogs for structure and composition, the linguistic structure of tweets approximate the linguistic patterns of natural language expressions. We find that microblogging is an online tool for customer word of mouth communications and discuss the implications for corporations using microblogging as part of their overall marketing strategy.

Topical classification of web queries has drawn recent interest because of the promise it offers in improving retrieval effectiveness and efficiency. However, much of this promise depends on whether classification is performed before or after the query is used to retrieve documents. We examine two previously unaddressed issues in query classification: pre versus post-retrieval classification effectiveness and the effect of training explicitly from classified queries versus bridging a classifier trained using a document taxonomy. Bridging classifiers map the categories of a document taxonomy onto those of a query classification problem to provide sufficient training data. We find that training classifiers explicitly from manually classified queries outperforms the bridged classifier by 48% in F1 score. Also, a pre-retrieval classifier using only the query terms performs merely 11% worse than the bridged classifier which requires snippets from retrieved documents.

Abstract The authors review a log of billions of Web queries that constituted the total query traffic for a 6‐month period of a general‐purpose commercial Web search service. Previously, query logs were studied from a single, cumulative view. In contrast, this study builds on the authors' previous work, which showed changes in popularity and uniqueness of topically categorized queries across the hours in a day. To further their analysis, they examine query traffic on a daily, weekly, and monthly basis by matching it against lists of queries that have been topically precategorized by human editors. These lists represent 13% of the query traffic. They show that query traffic from particular topical categories differs both from the query stream as a whole and from other categories. Additionally, they show that certain categories of queries trend differently over varying periods. The authors key contribution is twofold: They outline a method for studying both the static and topical properties of a very large query log over varying periods, and they identify and examine topical trends that may provide valuable insight for improving both retrieval effectiveness and efficiency.

Accurate topical classification of user queries allows for increased effectiveness and efficiency in general-purpose Web search systems. Such classification becomes critical if the system must route queries to a subset of topic-specific and resource-constrained back-end databases. Successful query classification poses a challenging problem, as Web queries are short, thus providing few features. This feature sparseness, coupled with the constantly changing distribution and vocabulary of queries, hinders traditional text classification. We attack this problem by combining multiple classifiers, including exact lookup and partial matching in databases of manually classified frequent queries, linear models trained by supervised learning, and a novel approach based on mining selectional preferences from a large unlabeled query log. Our approach classifies queries without using external sources of information, such as online Web directories or the contents of retrieved pages, making it viable for use in demanding operational environments, such as large-scale Web search services. We evaluate our approach using a large sample of queries from an operational Web search engine and show that our combined method increases recall by nearly 40% over the best single method while maintaining adequate precision. Additionally, we compare our results to those from the 2005 KDD Cup and find that we perform competitively despite our operational restrictions. This suggests it is possible to topically classify a significant portion of the query stream without requiring external sources of information, allowing for deployment in operationally restricted environments.

In dynamic environments, such as the World Wide Web, a changing document collection, query population, and set of search services demands frequent repetition of search effectiveness (relevance) evaluations. Reconstructing static test collections, such as in TREC, requires considerable human effort, as large collection sizes demand judgments deep into retrieved pools. In practice it is common to perform shallow evaluations over small numbers of live engines (often pairwise, engine A vs. engine B) without system pooling. Although these evaluations are not intended to construct reusable test collections, their utility depends on conclusions generalizing to the query population as a whole. We leverage the bootstrap estimate of the reproducibility probability of hypothesis tests in determining the query sample sizes required to ensure this, finding they are much larger than those required for static collections. We propose a semiautomatic evaluation framework to reduce this effort. We validate this framework against a manual evaluation of the top ten results of ten Web search engines across 896 queries in navigational and informational tasks. Augmenting manual judgments with pseudo-relevance judgments mined from Web taxonomies reduces both the chances of missing a correct pairwise conclusion, and those of finding an errant conclusion, by approximately 50%.

Search engines play an important role in helping users find desired content. With the increasing deployment of computerreadable privacy policies encoded using the standard W3C Platform for Privacy Preferences (P3P) format, search engines also have the potential to help users identify web sites that will respect their privacy needs. We conducted a study of the quantity and quality of P3P-encoded privacy policies associated with top-20 search results from three popular search engines. We built a P3P-enabled search engine and used it to gather statistics on P3P adoption as well as the privacy landscape of the Internet as a whole. This search engine makes use of a privacy policy cache that we designed to facilitate fast searches. Using a list of “typical ” search terms taken from AOL users ’ queries, we examined the trends in privacy policies that are returned from queries to the AOL, Google, and Yahoo! search engines. We then compared these results to results compiled after using “e-commerce search terms ” from Google’s Froogle service. We examined the top 20 search results returned by each search engine for each of the search terms and found at least one result with a P3P policy for 83 % of the typical search terms. Overall we found that these typical search terms yielded P3P adoption rates of 10%. This contrasts with adoption rates of 21 % percent when searching for e-commerce terms. Examining the content of the policies, we discovered that a minority of sites engage in direct marketing with or without a way of opting out, and that even fewer sites share personal information with other companies. Finally, we outline ways to increase P3P adoption rates as well as decrease policy errors.

We present a novel language modeling approach to capturing the query reformulation behavior of Web search users. Based on a framework that categorizes eight different types of "user moves" (adding/removing query terms, etc.), we treat search sessions as sequence data and build n-gram language models to capture user behavior. We evaluated our models in a prediction task. The results suggest that useful patterns of activity can be extracted from user histories. Furthermore, by examining prediction performance under different order n-gram models, we gained insight into the amount of history/context that is associated with different types of user actions. Our work serves as the basis for more refined user models.

With the amount of available text data in relational databases growing rapidly, the need for ordinary users to search such information is dramatically increasing. Even though the major RDBMSs have provided full-text search capabilities, they still require users to have knowledge of the database schemas and use a structured query language to search information. This search model is complicated for most ordinary users. Inspired by the big success of information retrieval (IR) style keyword search on the web, keyword search in relational databases has recently emerged as a new research topic. The differences between text databases and relational databases result in three new challenges: (1) Answers needed by users are not limited to individual tuples, but results assembled from joining tuples from multiple tables are used to form answers in the form of tuple trees. (2) A single score for each answer (i.e. a tuple tree) is needed to estimate its relevance to a given query. These scores are used to rank the most relevant answers as high as possible. (3) Relational databases have much richer structures than text databases. Existing IR strategies to rank relational outputs are not adequate. In this paper, we propose a novel IR ranking strategy for effective keyword search. We are the first that conducts comprehensive experiments on search effectiveness using a real world database and a set of keyword queries collected by a major search company. Experimental results show that our strategy is significantly better than existing strategies. Our approach can be used both at the application level and be incorporated into a RDBMS to support keyword-based search in relational databases.

Accurate topical classification of user queries allows for increased effectiveness and efficiency in general-purpose Web search systems. Such classification becomes critical if the system is to return results not just from a general Web collection but from topic-specific back-end databases as well. Maintaining sufficient classification recall is very difficult as Web queries are typically short, yielding few features per query. This feature sparseness coupled with the high query volumes typical for a large-scale search service makes manual and supervised learning approaches alone insufficient. We use an application of computational linguistics to develop an approach for mining the vast amount of unlabeled data in Web query logs to improve automatic topical Web query classification. We show that our approach in combination with manual matching and supervised learning allows us to classify a substantially larger proportion of queries than any single technique. We examine the performance of each approach on a real Web query stream and show that our combined method accurately classifies 46% of queries, outperforming the recall of best single approach by nearly 20%, with a 7% improvement in overall effectiveness.

We describe a method for improving the precision of metasearch results based upon scoring the visual features of documents' surrogate representations. These surrogate scores are used during fusion in place of the original scores or ranks provided by the underlying search engines. Visual features are extracted from typical search result surrogate information, such as title, snippet, URL, and rank. This approach specifically avoids the use of search engine-specific scores and collection statistics that are required by most traditional fusion strategies. This restriction correctly reflects the use of metasearch in practice, in which knowledge of the underlying search engines' strategies cannot be assumed. We evaluate our approach using a precision-oriented test collection of manually-constructed binary relevance judgments for the top ten results from ten web search engines over 896 queries. We show that our visual fusion approach significantly outperforms the rCombMNZ fusion algorithm by 5.71%, with 99% confidence, and the best individual web search engine by 10.9%, with 99% confidence.

Accurate topical categorization of user queries allows for increased effectiveness, efficiency, and revenue potential in general-purpose web search systems. Such categorization becomes critical if the system is to return results not just from a general web collection but from topic-specific databases as well. Maintaining sufficient categorization recall is very difficult as web queries are typically short, yielding few features per query. We examine three approaches to topical categorization of general web queries: matching against a list of manually labeled queries, supervised learning of classifiers, and mining of selectional preference rules from large unlabeled query logs. Each approach has its advantages in tackling the web query classification recall problem, and combining the three techniques allows us to classify a substantially larger proportion of queries than any of the individual techniques. We examine the performance of each approach on a real web query stream and show that our combined method accurately classifies 46% of queries, outperforming the recall of the best single approach by nearly 20%, with a 7% improvement in overall effectiveness.

We describe a method for predicting query difficulty in a precision-oriented web search task. Our approach uses visual features from retrieved surrogate document representations (titles, snippets, etc.) to predict retrieval effectiveness for a query. By training a supervised machine learning algorithm with manually evaluated queries, visual clues indicative of relevance are discovered. We show that this approach has a moderate correlation of 0.57 with precision at 10 scores from manual relevance judgments of the top ten documents retrieved by ten web search engines over 896 queries. Our findings indicate that difficulty predictors which have been successful in recall-oriented ad-hoc search, such as clarity metrics, are not nearly as correlated with engine performance in precision-oriented tasks such as this, yielding a maximum correlation of 0.3. Additionally, relying only on visual clues avoids the need for collection statistics that are required by these prior approaches. This enables our approach to be employed in environments where these statistics are unavailable or costly to retrieve, such as metasearch.

Detection of near duplicate documents is an important problem in many data mining and information filtering applications. When faced with massive quantities of data, traditional duplicate detection techniques relying on direct inter-document similarity computation (e.g., using the cosine measure) are often not feasible given the time and memory performance constraints. On the other hand, fingerprint-based methods, such as I-Match, are very attractive computationally but may be brittle with respect to small changes to document content. We focus on approaches to near-replica detection that are based upon large-collection statistics and present a general technique of increasing their robustness via multiple lexicon randomization. In experiments with large web-page and spam-email datasets the proposed method is shown to consistently outperform traditional I-Match, with the relative improvement in duplicate-document recall reaching as high as 40-60%. The large gains in detection accuracy are offset by only small increases in computational requirements.

We review a query log of hundreds of millions of queries that constitute the total query traffic for an entire week of a generalpurpose commercial web search service. Previously, query logs have been studied from a single, cumulative view. In contrast, our analysis shows changes in popularity and uniqueness of topically categorized queries across the hours of the day. We examine query traffic on an hourly basis by matching it against lists of queries that have been topically pre-categorized by human editors. This represents 13 % of the query traffic. We show that query traffic from particular topical categories differs both from the query stream as a whole and from other categories. This analysis provides valuable insight for improving retrieval effectiveness and efficiency. It is also relevant to the development of enhanced query disambiguation, routing, and caching algorithms.

We describe an evaluation of result set filtering techniques for providing ultra-high precision in the task of presenting related news for general web queries. In this task, the negative user experience generated by retrieving non-relevant documents has a much worse impact than not retrieving relevant ones. We adapt cost-based metrics from the document filtering domain to this result filtering problem in order to explicitly examine the tradeoff between missing relevant documents and retrieving non-relevant ones. A large manual evaluation of three simple threshold filters shows that the basic approach of counting matching title terms outperforms also incorporating selected abstract terms based on part-of-speech or higher-level linguistic structures. Simultaneously, leveraging these cost-based metrics allows us to explicitly determine what other tasks would benefit from these alternative techniques.

Abstract Prior efforts have shown that under certain situations retrieval effectiveness may be improved via the use of data fusion techniques. Although these improvements have been observed from the fusion of result sets from several distinct information retrieval systems, it has often been thought that fusing different document retrieval strategies in a single information retrieval system will lead to similar improvements. In this study, we show that this is not the case. We hold constant systemic differences such as parsing, stemming, phrase processing, and relevance feedback, and fuse result sets generated from highly effective retrieval strategies in the same information retrieval system. From this, we show that data fusion of highly effective retrieval strategies alone shows little or no improvement in retrieval effectiveness. Furthermore, we present a detailed analysis of the performance of modern data fusion approaches, and demonstrate the reasons why they do not perform well when applied to this problem. Detailed results and analyses are included to support our conclusions.

Evaluation of IR systems has always been difficult because of the need for manually assessed relevance judgments. The advent of large editor-driven taxonomies on the web opens the door to a new evaluation approach. We use the ODP (Open Directory Project) taxonomy to find sets of pseudo-relevant documents via one of two assumptions: 1) taxonomy entries are relevant to a given query if their editor-entered titles exactly match the query, or 2) all entries in a leaf-level taxonomy category are relevant to a given query if the category title exactly matches the query. We compare and contrast these two methodologies by evaluating six web search engines on a sample from an America Online log of ten million web queries, using MRR measures for the first method and precision-based measures for the second. We show that this technique is stable with respect to the query set selected and correlated with a reasonably large manual evaluation.

Prior research into search system scalability has primarily addressed query processing efficiency [1, 2, 3] or indexing efficiency [3], or has presented some arbitrary system architecture [4]. Little work has introduced any formal theoretical framework for evaluating architectures with regard to specific operational requirements, or for comparing architectures beyond simple timings [5] or basic simulations [6, 7]. In this paper, we present a framework based upon queuing network theory for analyzing search systems in terms of operational requirements. We use response time, throughput, and utilization as the key operational characteristics for evaluating performance. Within this framework, we present a scalability strategy that combines index partitioning and index replication to satisfy a given set of requirement.

We propose a novel approach that identifies web page templates and extracts the unstructured data. Extracting only the body of the page and eliminating the template increases the retrieval precision for the queries that generate irrelevant results. We believe that by reducing the number of irrelevant results; the users are encouraged to go back to a given site to search. Our experimental results on several different web sites and on the whole cnnfn collection demonstrate the feasibility of our approach.

Scalable information retrieval systems are crucial to meeting the growing volumes of data. We describe work done to facilitate scalability by reducing duplication, providing integration with structured data, and supporting integration and question answering via an intranet mediator. All examples given are taken directly from prior and on-going efforts in the IIT Information Retrieval Laboratory in collaboration with AOL and NCR.

Information retrieval system evaluation is complicated by the need for manually assessed relevance judgments. Large manually-built directories on the web open the door to new evaluation procedures. By assuming that web pages are the known relevant items for queries that exactly match their title, we use the ODP (Open Directory Project) and Looksmart directories for system evaluation. We test our approach with a sample from a log of ten million web queries and show that such an evaluation is unbiased in terms of the directory used, stable with respect to the query set selected, and correlated with a reasonably large manual evaluation.

Cosine Pivoted Document Length Normalization has reached a point of stability where many researchers indiscriminately apply a specific value of 0.2 regardless of the collection. Our efforts, however, demonstrate that applying this specific value without tuning for the document collection degrades average precision by as much as 20%.

Users of the World-Wide Web are not only confronted by an immense overabundance of information, but also by a plethora of tools for searching for the web pages that suit their information needs. Web search engines differ widely in interface, features, coverage of the web, ranking methods, delivery of advertising, and more. In this paper, we present a method for comparing search engines automatically based on how they rank known item search results. Because the engines perform their search on overlapping (but different) subsets of the web collected at different points in time, evaluation of search engines poses significant challenges to the traditional information retrieval methodology. Our method uses known item searching; comparing the relative ranks of the items in the search engines' rankings. Our approach automatically constructs known item queries using query log analysis and automatically constructs the result via analysis of editor comments from the ODP (Open Directory Project). Additionally, we present our comparison on five (Lycos, Netscape, Fast, Google, HotBot) well-known search services and find that some services perform known item searches better than others, but the majority are statistically equivalent.

We present a new algorithm for duplicate document detection that uses collection statistics. We compare our approach with the state-of-the-art approach using multiple collections. These collections include a 30 MB 18,577 web document collection developed by Excite@Home and three NIST collections. The first NIST collection consists of 100 MB 18,232 LA-Times documents, which is roughly similar in the number of documents to the Excite&at;Home collection. The other two collections are both 2 GB and are the 247,491-web document collection and the TREC disks 4 and 5---528,023 document collection. We show that our approach called I-Match, scales in terms of the number of documents and works well for documents of all sizes. We compared our solution to the state of the art and found that in addition to improved accuracy of detection, our approach executed in roughly one-fifth the time.

No abstract available.

We present performance measurement results for a parallel SQL based information retrieval system implemented on a PC cluster system. We used the Web-TREC dataset under a left-deep query execution plan. We achieved satisfactory speed up.

We present a method of searching text collections that takes advantage of hierarchrical information within documents and integrates searches of structured and unstructured data. We show that Multidimensional databases (MDB), designed for accessing data along hierarchical dimensions, are effective for information retrieval. We demonstrate a method of using On-Line Analytic Processing (OLAP) techniques on a text collection. This combines traditional information retrieval and the slicing, dicing, drill-down, and roll-up of OLAP. We demonstrate use of a prototype for searching documents from the TREC collection.

Prior work has shown that combining results of various retrieval approaches and query representations can improve search effectiveness. Today, many meta-search engines exist which combine the results of various search engines in the hopes of improving overall effectiveness. However, the combination of results from different search engines masks variations in parsers, and other indexing techniques (stemming, stop words, etc.) This makes it difficult to assess the utility of the fusion technique. We have implemented the two most prevalent retrieval strategies: probabilistic and vector space using the same parser and the same relational retrieval engine. First, we identified a model that enables the fusion of an arbitrary number of sources. Next, we tested various linear combinations of these two methods as well as various thresholds for identifying retrieved documents. Our results show some improvement of effectiveness, but they also provide us for a baseline from which we can continue with other retrieval strategies and test the effect of fusing these strategies.

We present a novel proactive routing algorithm (dynamic routing system, DRS) that consistently searches for failures via frequent ICMP (Internet control message protocol) echo requests. Our algorithm differs from its predecessors in that it is proactive instead of reactive by looking for failures before they affect message transmissions. When a failure is detected, an alternative route is identified and used. Based on our actual implementation, we developed an analytical model of the DRS to evaluate its potential use for large networks. Using this model, we computed for various network sizes the fault identification times given a percentage of network usage. Calculations are carried out for a typical 10 Mbs Ethernet.

Clusters of workstations are increasingly being viewed as a cost effective alternative to parallel supercomputers. However, resource management and scheduling on workstations clusters is complicated by the fact that the number of idle workstations available for executing parallel applications is constantly fluctuating. We present a case for scheduling parallel applications on non dedicated workstation clusters using dynamic space sharing, a policy under which the number of processors allocated to an application can be changed during its execution. We describe an approach that uses application level checkpointing and data repartitioning for supporting dynamic space sharing and for handling the dynamic reconfiguration triggered when failure or owner activity is detected on a workstation being used by a parallel application. The performance advantages of dynamic space sharing are quantified through a simulation study, and experimental results are presented for the overhead of dynamic reconfiguration of a grid oriented data parallel application using our approach.