Multi-modal Salient Object Detection (SOD) shows an improvement over its uni-modal counterpart by exploiting the complementary benefits between modalities. However, this improvement relies on complete multi-modal information, which is difficult to be guaranteed in practice due to sensor failures and transmission errors. To address this issue, we propose a robust multi-modal SOD framework that enhances the adaptability to modality-missing conditions, while maintaining comparable performance in the modality-complete condition. Nevertheless, flexibly handling modality-missing and modality-complete cases and integrating their corresponding multi-modal features in a unified framework is non-trivial. To this end, we achieve this framework by designing a Cascaded Mixture-of-Experts (CMoE) network that sequentially incorporates missing-aware and multi-modal MoE. Specifically, the missing-aware MoE employs three modality-reconstruction experts with a soft router to adaptively reconstruct feature representations for both missing and available modalities, assisted by an expert modulation loss that guides the router to assign expert weights according to missing conditions. The multi-modal MoE adopts two homogeneous uni-modal experts with learned modality-specific knowledge tailored for integrating modality features, which are dynamically combined via the soft router. The cascaded architecture fully empowers CMoE with the flexibility across varying input cases. Extensive experiments on modality-missing and modality-complete conditions demonstrate the effectiveness of the proposed method.

Alignment-free RGB-Thermal (RGB-T) salient object detection (SOD) aims to achieve robust performance in complex scenes by directly leveraging the complementary information from unaligned visible-thermal image pairs, without requiring manual alignment. However, the labor-intensive process of collecting and annotating image pairs limits the scale of existing benchmarks, hindering the advancement of alignment-free RGB-T SOD. In this paper, we construct a large-scale and high-diversity unaligned RGB-T SOD dataset named UVT20K, comprising 20,000 image pairs, 407 scenes, and 1256 object categories. All samples are collected from real-world scenarios with various challenges, such as low illumination, image clutter, complex salient objects, and so on. To support the exploration for further research, each sample in UVT20K is annotated with a comprehensive set of ground truths, including saliency masks, scribbles, boundaries, and challenge attributes. In addition, we propose a Progressive Correlation Network (PCNet), which models inter- and intra-modal correlations on the basis of explicit alignment to achieve accurate predictions in unaligned image pairs. Extensive experiments conducted on two unaligned three weakly aligned three aligned datasets demonstrate the effectiveness of our method.

Approximate machine unlearning aims to remove the effect of specific data from trained models to ensure individuals' privacy. Existing methods focus on the removed records and assume the retained ones are unaffected. However, recent studies on the privacy onion effect indicate this assumption might be incorrect. Especially when the model is differentially private, no study has explored whether the retained ones still meet the differential privacy (DP) criteria under existing machine unlearning methods. This paper takes a holistic approach to auditing both unlearned and retained samples' privacy risks after applying approximate unlearning algorithms. We propose the privacy criteria for unlearned and retained samples, respectively, based on the perspectives of DP and membership inference attacks (MIAs). To make the auditing process more practical, we also develop an efficient MIA, A-LiRA, utilizing data augmentation to reduce the cost of shadow model training. Our experimental findings indicate that existing approximate machine unlearning algorithms may inadvertently compromise the privacy of retained samples for differentially private models, and that we need differentially private unlearning algorithms. For reproducibility, we have published our code: https://anonymous.4open.science/r/Auditing-machine-unlearning-CB10/README.md

With increasingly deployed deep neural networks in sensitive application domains, such as healthcare and security, it's essential to understand what kind of sensitive information can be inferred from these models. Most known model-targeted attacks assume attackers have learned the application domain or training data distribution to ensure successful attacks. Can removing the domain information from model APIs protect models from these attacks? This paper studies this critical problem. Unfortunately, even with minimal knowledge, i.e., accessing the model as an unnamed function without leaking the meaning of input and output, the proposed adaptive domain inference attack (ADI) can still successfully estimate relevant subsets of training data. We show that the extracted relevant data can significantly improve, for instance, the performance of model-inversion attacks. Specifically, the ADI method utilizes the concept hierarchy extracted from the public and private datasets that the attacker can access and applies a novel algorithm to adaptively tune the likelihood of leaf concepts in the hierarchy showing up in the unseen training data. For comparison, we also designed a straightforward hypothesis-testing-based attack -- LDI. The ADI attack not only extracts partial training data at the concept level but also converges fastest and requires the fewest target-model accesses among all candidate methods. Our code is available at https://anonymous.4open.science/r/KDD-362D.

RecSys '25: Nineteenth ACM Conference on Recommender Systems Prague Czech Republic September 22 - 26, 2025

Trusted execution environments (TEEs) enable efficient protection of integrity and confidentiality for applications running on untrusted platforms. They have been deployed in cloud servers to attract users who have concerns on exporting data and computation. However, recent studies show that TEEs’ side channels, including memory, cache, and micro-architectural features, are still vulnerable to adversarial exploitation. As many such attacks utilize program access patterns to infer secret information , data oblivious programs have been considered a practical defensive solution. However, they are often difficult to develop and optimize via either manual or automated approaches. We present the oblivious TEE with MapReduce (TEE-MR) approach that uses application frameworks, an approach between fully manual and fully automated, to hide the details of access-pattern protection to significantly minimize developers’ efforts. We have implemented the approach with the MapReduce application framework for data-intensive applications. It can regulate application dataflows and hide application-agnostic access-pattern protection measures from developers. Compared to manual composition approaches, it demands much less effort for developers to identify access patterns and to write code. Our approach is also easy to implement, less complicated than fully automated approaches , for which we have not seen a working prototype yet. Our experimental results show that TEE-MR-based applications have good performance , comparable to those carefully developed with time-consuming manual composition approaches.

Weakly supervised group activity recognition (WSGAR) aims at identifying the overall behavior of multiple persons without any fine-grained supervision information (including individual position and action label). Traditional methods usually adopt a person-to-whole way: detect persons via off-the-shelf detectors, obtain person-level features, and integrate into the group-level features for training the classifier. However, these methods are unflexible due to serious reliance on the quality of detectors. To get rid of the detector, recent works learn several prototype tokens from noisy grid features with learnable weights directly, which treat all the local visual information equally and bring in redundant and ambiguous information to some extent. To this end, we propose a novel coarse-fine nested network (CFNN) to coarsely localize the key visual patches of activity and further finely learn the local features, as well as the global features. Specifically, we design a nested interactor (NI) to progressively model the spatiotemporal interactions of the learnable global token. According to the cue of spatial interaction in NI, we localize several key visual patches via a new coarse-grained spatial localizer (CSL). Then, we finally encode these localized visual patches with the help of global spatiotemporal dependency via a new fine-grained spatiotemporal selector (FSS). Extensive experiments on Volleyball and NBA datasets demonstrate the effectiveness of the proposed CFNN compared with the existing competitive methods. Code is available at: https://github.com/gexiaojingshelby/CFNN.

Differential privacy quantifies privacy through the privacy budget , yet its practical interpretation is complicated by variations across models and datasets. Recent research on differentially private machine learning and membership inference has highlighted that with the same theoretical setting, the likelihood-ratio-based membership inference (LiRA) attack success rate (ASR) may vary according to specific datasets and models, which might be a better indicator for evaluating real-world privacy risks. Inspired by this practical privacy measure, we study the positive correlation between the setting and ASR. We also find that for a specific dataset and a specific task we can lower the attack success rate by modifying the dataset. As a result, we may enable flexible privacy budget settings in model training. One dataset modification strategy is selectively suppressing privacy-sensitive features without significantly damaging application-specific data utility. We use the SHAP (or LIME) model explainer to evaluate features’ privacy sensitivity and utility importance and develop an optimized feature-masking algorithm. We have conducted extensive experiments to show (1) the inherent link between ASR and the dataset’s privacy risk in terms of a specific modeling task; (2) By carefully selecting features to mask, we can preserve more data utility with equivalent practical privacy protection and relaxed settings. The implementation details are shared online at https://github.com/RhincodonE/On-sensitive-features-and-empirical-epsilon-lower-bounds.

Data privacy has been a top concern in the AI era. Despite the recent development of differentially private learning methods, controlled data access remains a mainstream method for protecting data privacy in many industrial and research environments. In controlled data access, authorized model builders work in a restricted environment to access sensitive data, which can fully preserve data utility with reduced risk of data leak. However, unlike differential privacy, there is no quantitative measure for individual data contributors to tell their privacy risk before participating in a machine learning task. We developed the demo prototype FT-PrivacyScore to show that it's possible to efficiently and quantitatively estimate the privacy risk of participating in a model fine-tuning task. The demo source code will be available at https://github.com/RhincodonE/demo_privacy_scoring.

Trusted Execution Environments (TEEs) are gradually adopted by major cloud providers, offering a practical option of confidential computing for users who do not fully trust public clouds. TEEs use CPU -enabled hardware features to eliminate direct breaches from compromised operating systems or hypervisors. However, recent studies have shown that side-channel attacks are still effective on TEEs. An appealing solution is to convert applications to be data oblivious to deter many side-channel attacks. While a few research prototypes on TEEs have adopted specific data oblivious operations, the general conversion approaches have never been thoroughly compared against and tested on benchmark TEE applications. These limitations make it difficult for researchers and practitioners to choose and adopt a suitable data oblivious approach. To address these issues, we conduct a comprehensive analysis of representative conversion approaches and perform an extensive empirical study to provide insights into their performance and ease of use with benchmark TEE applications.

Model-based attacks can infer training data information from deep neural network models. These attacks heavily depend on the attacker's knowledge of the application domain, e.g., using it to determine the auxiliary data for model-inversion attacks. However, attackers may not know what the model is used for in practice. We propose a generative adversarial network (GAN) based method to explore likely or similar domains of a target model -- the model domain inference (MDI) attack. For a given target (classification) model, we assume that the attacker knows nothing but the input and output formats and can use the model to derive the prediction for any input in the desired form. Our basic idea is to use the target model to affect a GAN training process for a candidate domain's dataset that is easy to obtain. We find that the target model may distort the training procedure less if the domain is more similar to the target domain. We then measure the distortion level with the distance between GAN-generated datasets, which can be used to rank candidate domains for the target model. Our experiments show that the auxiliary dataset from an MDI top-ranked domain can effectively boost the result of model-inversion attacks.

Deep learning training involves large training data and expensive model tweaking, for which cloud GPU resources can be a popular option. However, outsourcing data often raises privacy concerns. The challenge is to preserve data and model confidentiality without sacrificing GPU-based scalable training and low-cost client-side preprocessing, which is difficult for conventional cryptographic solutions to achieve. This demonstration shows a new approach, image disguising, represented by recent work: DisguisedNets, NeuraCrypt, and InstaHide, which aim to securely transform training images while still enabling the desired scalability and efficiency. We present an interactive system for visually and comparatively exploring these methods. Users can view disguised images, note low client-side processing costs, and observe the maintained efficiency and model quality during server-side GPU-accelerated training. This demo aids researchers and practitioners in swiftly grasping the advantages and limitations of image-disguising methods.

Trusted Execution Environments, such as Intel SGX, use hardware supports to ensure the confidentiality and integrity of applications against a compromised cloud system. However, side channels like access patterns remain for adversaries to exploit and obtain sensitive information. Common approaches use oblivious programs or primitives, such as ORAM, to make access patterns oblivious to input data, which are challenging to develop. This demonstration shows a prototype SGX-MR-Prot for efficiently protecting access patterns of SGX-based data-intensive applications and minimizing developers' efforts. SGX-MR-Prot uses the MapReduce framework to regulate application dataflows to reduce the cost of access-pattern protection and hide the data oblivious details from SGX developers. This demonstration will allow users to intuitively understand the unique contributions of the framework-based protection approach via interactive exploration and visualization.

Spatio-temporal Action Detection (SAD) aims to recognize the multi-class actions, and meanwhile locate their spatio-temporal occurrence in untrimmed videos. Besides relying on the inherent inter-actor interactions, most previous SAD approaches model actor interactions between multi-actors and the whole frames or special parts (e.g., objects/hands). However, such approaches are relatively graceless by 1) roughly treating all various actors to equivalently interact with frames/parts or by 2) sumptuously borrowing multiple costly detectors to acquire the special parts. To solve the above dilemma, we propose a novel Foreground/Background-masked Interaction Learning (dubbed as FBI Learning) framework to learn the multi-actor features by attentively interacting with the hands-down foreground and background frames. Specifically, we first design a new Mask-guided Cross Attention (MCA) mechanism that calculates the masked cross-attentions to capture the compact relations between the actors and foreground/background regions. Next, we present a new Actor-guided Feature Aggregation (AFA) scheme that integrates foreground- and background-interacted actor features with the learnable actor-based weights. Finally, we construct a long-term feature bank that associates temporal context information to facilitate action classification. Extensive experiments are conducted on commonly available UCF101-24, MultiSports, and AVA v2.1/v2.2 datasets, which illustrate the competitive performance of FBI Learning against the state-of-the-art methods.

Large training data and expensive model tweaking are standard features of deep learning with images. As a result, data owners often utilize cloud resources to develop large-scale complex models, which also raises privacy concerns. Existing cryptographic solutions for training deep neural networks (DNNs) are too expensive, cannot effectively utilize cloud GPU resources, and also put a significant burden on client-side pre-processing. This article presents an image disguising approach: DisguisedNets, which allows users to securely outsource images to the cloud and enables confidential, efficient GPU-based model training. DisguisedNets uses a novel combination of image blocktization, block-level random permutation, and block-level secure transformations: random multidimensional projection (RMT) or AES pixel-level encryption (AES) to transform training data. Users can use existing DNN training methods and GPU resources without any modification to training models with disguised images. We have analyzed and evaluated the methods under a multi-level threat model and compared them with another similar method—InstaHide. We also show that the image disguising approach, including both DisguisedNets and InstaHide, can effectively protect models from model-targeted attacks.

Clothes changing is one of the challenges in person re-identification (ReID), since clothes provide remarkable and reliable information for decision, especially when the resolution of an image is low. Variation of clothes significantly downgrades standard ReID models, since the clothes information dominates the decisions. The performance of the existing methods considering clothes changing is still not satisfying, since they fail to extract sufficient identity information that excludes clothes information. This study aims to disentangle identity, clothes, and unrelated features with a Generative Adversarial Network (GAN). A GAN model with three encoders, one generator, and three discriminators, and its training procedure are proposed to learn these kinds of features separately and exclusively. Experimental results indicate that our model generally achieves the best performance among state-of-the-art methods in both ReID tasks with and without clothes changing, which confirms that the identity, clothes, and unrelated features are extracted by our model more precisely and effectively.

Large training data and expensive model tweaking are common features of deep learning development for images. As a result, data owners often utilize cloud resources or machine learning service providers for developing large-scale complex models. This practice, however, raises serious privacy concerns. Existing solutions are either too expensive to be practical, or do not sufficiently protect the confidentiality of data and model. In this paper, we aim to achieve a better trade-off among the level of protection for outsourced DNN model training, the expenses, and the utility of data, using novel image disguising mechanisms. We design a suite of image disguising methods that are efficient to implement and then analyze them to understand multiple levels of tradeoffs between data utility and protection of confidentiality. The experimental evaluation shows the surprising ability of DNN modeling methods in discovering patterns in disguised images and the flexibility of these image disguising mechanisms in achieving different levels of resilience to attacks.

The development of the next-generation sequencing technology has enabled systems immunology researchers to conduct detailed immune repertoire analysis at the molecular level that allows researchers to understand the healthiness of a patient’s immune system. Recent studies have shown that the single-linkage clustering algorithm can give the best results for B cell clonality analysis – a critical type of immune repertoire sequencing (IR-Seq) analysis. Large sequence datasets (e.g., millions of sequences) are being collected to comprehensively understand how a specific person’s immune system evolves over different stages of disease development. However, the classical single-linkage clustering algorithm does not scale well to such large sequence datasets. Surprisingly, no study has been done to address this scalability issue for immunology research and development. We study three different strategies to scale up the single-linkage algorithm for sequence data. They include (1) the approximate single-linkage algorithm enhanced with the non-Euclidean indexing methods, (2) the Spark-based single-linkage algorithm (SparkMST) that was originally designed for vector data and now modified for sequence data, and (3) a new tree-based sequence summarization approach – SCT that aims to reduce the data for single-linkage clustering with well-preserved clustering quality.We have implemented these approaches and experimented with real sequence datasets for B cell clonality analysis. (1) The index-enhanced hierarchical clustering algorithm (e.g., VPT-HC using the Vantage-Point tree for indexing) preserves the clustering quality very well while significantly reducing the time complexity. (2) The SCT approach serving as a preprocessing step can effectively reduce data size for clustering. The overall clustering, SCT followed by VPT-HC, is the fastest among the evaluated single-machine algorithms. However, this approach also slightly affects the clustering quality. (3) The SparkMST parallel algorithm scales out nicely and also gives exact single-linkage clustering results. However, SparkMST is tied to the single-linkage algorithm and cannot be extended to general hierarchical clustering algorithms. Although this study focused on the specific application area: the B cell clonality analysis, we believe other sequence data analysis problems may find the developed scalable techniques useful.

Image-level weakly supervised semantic segmentation (WSSS) reduces the cost of semantic segmentation significantly as only category labels are required. In the WSSS pipeline, the initially obtained seed areas are imprecise and should be refined. AffinityNet is a widely used seed area refinement method which learns pixel-level affinity between coordinates to adjust the object regions. However, the capabilities of AffinityNet are limited due to the complex simultaneous exploration of the affinities of all object classes, as the classes have different characteristics. This paper proposes a class-specific AffinityNet (CSANet) in which the affinities of each class are learnt separately by the class-specific affinity layers. Moreover, as the learning task is simple because the affinity of only one class is focused, the information contained by the uncertain neutral regions is extracted to provide additional information in the training of the class-specific affinity layers. The empirical results demonstrate the effectiveness of our method, which captures more precise boundaries and significantly improves segmentation results on the PASCAL VOC 2012 segmentation benchmark.

With the ever-growing data and the need for developing powerful machine learning models, data owners increasingly depend on various untrusted platforms (e.g., public clouds, edges, and machine learning service providers) for scalable processing or collaborative learning. Thus, sensitive data and models are in danger of unauthorized access, misuse, and privacy compromises. A relatively new body of research confidentially trains machine learning models on protected data to address these concerns. In this survey, we summarize notable studies in this emerging area of research. With a unified framework, we highlight the critical challenges and innovations in outsourcing machine learning confidentially. We focus on the cryptographic approaches for confidential machine learning (CML), primarily on model training, while also covering other directions such as perturbation-based approaches and CML in the hardware-assisted computing environment. The discussion will take a holistic way to consider a rich context of the related threat models, security assumptions, design principles, and associated trade-offs amongst data utility, cost, and confidentiality.

Abstract Intel SGX has been a popular trusted execution environment (TEE) for protecting the integrity and confidentiality of applications running on untrusted platforms such as cloud. However, the access patterns of SGX-based programs can still be observed by adversaries, which may leak important information for successful attacks. Researchers have been experimenting with Oblivious RAM (ORAM) to address the privacy of access patterns. ORAM is a powerful low-level primitive that provides application-agnostic protection for any I/O operations, however, at a high cost. We find that some application-specific access patterns, such as sequential block I/O, do not provide additional information to adversaries. Others, such as sorting, can be replaced with specific oblivious algorithms that are more efficient than ORAM. The challenge is that developers may need to look into all the details of application-specific access patterns to design suitable solutions, which is time-consuming and error-prone. In this paper, we present the lightweight SGX based MapReduce (SGX-MR) approach that regulates the dataflow of data-intensive SGX applications for easier application-level access-pattern analysis and protection. It uses the MapReduce framework to cover a large class of data-intensive applications, and the entire framework can be implemented with a small memory footprint. With this framework, we have examined the stages of data processing, identified the access patterns that need protection, and designed corresponding efficient protection methods. Our experiments show that SGX-MR based applications are much more efficient than the ORAM-based implementations.

Recent studies show that by combining network topology and node attributes, we can better understand community structures in complex networks. However, existing algorithms do not explore "contextually" similar node attribute values, and therefore may miss communities defined with abstract concepts. We propose a community detection and characterization algorithm that incorporates the contextual information of node attributes described by multiple domain-specific hierarchical concept graphs. The core problem is to find the context that can best summarize the nodes in communities, while also discovering communities aligned with the context summarizing communities. We formulate the two intertwined problems, optimal community-context computation, and community discovery, with a coordinate-ascent based algorithm that iteratively updates the nodes' community label assignment with a community-context and computes the best context summarizing nodes of each community. Our unique contributions include (1) a composite metric on Informativeness and Purity criteria in searching for the best context summarizing nodes of a community; (2) a node similarity measure that incorporates the context-level similarity on multiple node attributes; and (3) an integrated algorithm that drives community structure discovery by appropriately weighing edges. Experimental results on public datasets show nearly 20 percent improvement on F-measure and Jaccard for discovering underlying community structure over the current state-of-the-art of community detection methods. Community structure characterization was also accurate to find appropriate community types for four datasets.

Big graphs, such as user interactions in social networks and customer rating matrices in collaborative filters, possess great values for both businesses and research. They are not only big but often keep evolving, which requires a large amount of computing resources to maintain. With the wide deployment of public cloud resources, owners of big graphs may want to use cloud resources to obtain storage and computation scalability. However, privacy and ownership of the graphs in the cloud has become a major concern. In this paper, we study privacy-preserving algorithms for one of the important graph analysis techniques-graph spectral analysis for outsourced graph in the cloud. The core operation: eigendecomposition of large matrix is also important to many data mining algorithms. We consider a cloud-centric framework with three collaborative parties: data contributors, data owner, and cloud provider. Graphs are represented as matrices such as adjacency matrix and Laplacian matrix, the elements of which are encrypted and submitted by distributed contributors. The data owner then interacts with the cloud-side programs to conduct spectral analysis, while protecting data privacy from the honest-but-curious cloud provider. For a N × N graph matrix, we aim to design algorithms with the cloud handling expensive storage and computation in O(N2) complexity, while data owner and data contributors' algorithms take only O(N). To achieve this goal, we develop the privacy-preserving versions of the two approximate eigendecomposition algorithms: the Lanczos algorithm and the Nyström algorithm, considering two encryption methods: additive homomorphic encryption (AHE) methods and somewhat homomorphic encryption (SHE) methods. Both dense and sparse matrices are studied, while sparse matrices also involve a differentially private data submission protocol to allow the trade-off between data sparsity and privacy. Experimental results show that the Nyströ algorithm with sparse encoding can dramatically reduce data owners' costs. SHE-based methods have lower computational time while AHE-based methods have lower communication/storage costs.

Due to the high training costs of deep learning, model developers often rent cloud GPU servers to achieve better efficiency. However, this practice raises privacy concerns. An adversarial party may be interested in 1) personal identifiable information encoded in the training data and the learned models, 2) misusing the sensitive models for its own benefits, or 3) launching model inversion (MIA) and generative adversarial network (GAN) attacks to reconstruct replicas of training data (e.g., sensitive images). Learning from encrypted data seems impractical due to the large training data and expensive learning algorithms, while differential-privacy based approaches have to make significant trade-offs between privacy and model quality. We investigate the use of image disguising techniques to protect both data and model privacy. Our preliminary results show that with block-wise permutation and transformations, surprisingly, disguised images still give reasonably well performing deep neural networks (DNN). The disguised images are also resilient to the deep-learning enhanced visual discrimination attack and provide an extra layer of protection from MIA and GAN attacks.

We propose SecureBoost, a privacy-preserving predictive modeling framework, that allows service providers (SPs) to build powerful boosting models over encrypted or randomly masked user submitted data. SecureBoost uses random linear classifiers (RLCs) as the base classifiers. A Cryptographic Service Provider (CSP) manages keys and assists the SP's processing to reduce the complexity of the protocol constructions. The SP learns only the base models (i.e., RLCs) and the CSP learns only the weights of the base models and a limited leakage function. This separated parameter holding avoids any party from abusing the final model or conducting model-based attacks. We evaluate two constructions of SecureBoost: HE+GC and SecSh+GC using combinations of primitives - homomorphic encryption, garbled circuits, and random masking. We show that SecureBoost efficiently learns high-quality boosting models from protected user-generated data with practical costs.

Collaborative filtering (CF) is vulnerable under shilling attack, which misleads recommendation of CF by injecting well-crafted profiles to a targeted system. Although a number of supervised learning based shilling attack detection methods are proposed, their features mainly measure rating values and items of a profile individually, but ignore the relation between items. This study aims to enhance the robustness of CF against shilling attack by considering the rated item correlation. Real users rate items based on their preferences, but rated items are randomly selected for malicious users profiles in most shilling attack. Therefore, the rated item correlation of real and malicious profiles is different. Three features are proposed to capture the information from different intervals of the distribution of rated item correlation in terms of Cosine Association (CA). A benchmark dataset, MovieLens 100K, is used to evaluate the proposed features. The discrimination ability of the proposed features is also illustrated. The experimental results suggest that the proposed features have significant contribution on shilling attack detection.

Mining large data requires intensive computing resources and data mining expertise, which might be unavailable for many users. With widely available cloud computing resources, data mining tasks can now be moved to the cloud or outsourced to third parties to save costs. In this new paradigm, data and model confidentiality becomes the major concern to the data owner. Data owners have to understand the potential trade-offs among client-side costs, model quality, and confidentiality to justify outsourcing solutions. In this paper, we propose the RASP-Boost framework to address these problems in confidential cloud-based learning. The RASP-Boost approach works with our previous developed RAndom Space Perturbation (RASP) method to protect data confidentiality and uses the boosting framework to overcome the difficulty of learning high-quality classifiers from RASP perturbed data. We develop several cloudclient collaborative boosting algorithms. These algorithms require low client-side computation and communication costs. The client does not need to stay online in the process of learning models. We have thoroughly studied the confidentiality of data, model, and learning process under a practical security model. Experiments on public datasets show that the RASP-Boost approach can provide high-quality classifiers, while preserving high data and model confidentiality and requiring low client-side costs.

Graph datasets have invaluable use in business applications and scientific research. Because of the growing size and dynamically changing nature of graphs, graph data owners may want to use public cloud infrastructures to store, process, and perform graph analytics. However, when outsourcing data and computation, data owners are at burden to develop methods to preserve data privacy and data ownership from curious cloud providers. This demonstration exhibits a prototype system for privacy-preserving spectral analysis framework for large graphs in public clouds (PrivateGraph) that allows data owners to collect graph data from data contributors, and store and conduct secure graph spectral analysis in the cloud with preserved privacy and ownership. This demo system lets its audience interactively learn the major cloud-client interaction protocols: the privacy-preserving data submission, the secure Lanczos and Nyström approximate eigen-decomposition algorithms that work over encrypted data, and the outcome of an important application of spectral analysis - spectral clustering. In the process of demonstration the audience will understand the intrinsic relationship amongst costs, result quality, privacy, and scalability of the framework.

This paper exploits a large number of self-labeled emotion tweets as the training data from the source domain to improve emotion identification in target domains (i.e., blogs and fairy tales), where there is a short supply of labeled data. Due to the noisy and ambiguous nature of self-labeled emotion training data, the existing domain adaptation methods that typically depend on high-quality labeled source-domain data do not work satisfactorily. This paper describes an adaptive source-domain training instance selection method to address the problem of noisy source-domain training data. The proposed approach can effectively identify the most informative training examples based on three carefully designed measures: consistency, diversity, and similarity. It uses an iterative method that consists of the following steps in each iteration: selecting informative samples from the source domain with the informativeness measures, merging with the target-domain training data, evaluating the performance of learned classifier for the target domain, and updating the informativeness measures for the next iteration. It stops until no new training instance is selected or in a designated number of iterations. Experiments show that our approach performs effectively for cross-domain emotion identification and consistently outperforms baseline approaches across four domains.

Lineage analysis has been an important method for understanding the mutation patterns and the diversity of genes, such as antibodies. A mutation lineage is typically represented as a tree structure, describing the possible mutation paths. Generating lineage trees from sequence data imposes two unique challenges: (1) Types of constraints might be defined on top of sequence data and tree structures, which have to be appropriately formulated and maintained by the algorithms. (2) Enumerating all possible trees that satisfy constraints is typically computationally intractable. In this paper, we present a COnstrained Lineage Tree generation framework (COLT) that builds lineage trees from sequences, based on local and global constraints specified by domain experts and heuristics derived from the mutation processes. Our formal analysis and experimental results show that this framework can efficiently generate valid lineage trees, while strictly satisfying the constraints specified by domain experts.

Large graph datasets have become invaluable assets for studying problems in business applications and scientific research. These datasets, collected and owned by data owners, may also contain privacy-sensitive information. When using public clouds for elastic processing, data owners have to protect both data ownership and privacy from curious cloud providers. We propose a cloud-centric framework that allows data owners to efficiently collect graph data from the distributed data contributors, and privately store and analyze graph data in the cloud. Data owners can conduct expensive operations in untrusted public clouds with privacy and scalability preserved. The major contributions of this work include two privacy-preserving approximate eigen decomposition algorithms (the secure Lanczos and Nystrom methods) for spectral analysis of large graph matrices, and a personalized privacy-preserving data submission method based on differential privacy that allows for the trade-off between data sparsity and privacy. For a N-node graph, the proposed approach allows a data owner to finish the core operations with only O(N) client-side costs in computation, storage, and communication. The expensive O(N2) operations are performed in the cloud with the proposed privacy-preserving algorithms. We prove that our approach can satisfactorily preserve data privacy against the untrusted cloud providers. We have conducted an extensive experimental study to investigate these algorithms in terms of the intrinsic relationships among costs, privacy, scalability, and result quality.

Inappropriate tweets can cause severe damages on authors' reputation or privacy. However, many users do not realize the negative consequences until they publish these tweets. Published tweets have lasting effects that may not be eliminated by simple deletion because other users may have read them or third-party tweet analysis platforms have cached them. Regrettable tweets, i.e., tweets with identifiable regrettable contents, cause the most damage on their authors because other users can easily notice them. In this paper, we study how to identify the regrettable tweets published by \emph{normal individual users} via the contents and users' historical deletion patterns. We identify normal individual users based on their publishing, deleting, followers and friends statistics. We manually examine a set of randomly sampled deleted tweets from these users to identify regrettable tweets and understand the corresponding regrettable reasons. By applying content-based features and personalized history-based features, we develop classifiers that can effectively predict regrettable tweets.

Euclidean embedding algorithms transform data defined in an arbitrary metric space to the Euclidean space, which is critical to many visualization techniques. At big-data scale, these algorithms need to be scalable to massive data-parallel infrastructures. Designing such scalable algorithms and understanding the factors affecting the algorithms are important research problems for visually analyzing big data. We propose a framework that extends the existing Euclidean embedding algorithms to scalable ones. Specifically, it decomposes an existing algorithm into naturally parallel components and non-parallelizable components. Then, data parallel implementations such as MapReduce and data reduction techniques are applied to the two categories of components, respectively. We show that this can be possibly done for a collection of embedding algorithms. Extensive experiments are conducted to understand the important factors in these scalable algorithms: scalability, time cost, and the effect of data reduction to result quality. The result on sample algorithms: Fast Map-MR and LMDS-MR shows that with the proposed approach the derived algorithms can preserve result quality well, while achieving desirable scalability.

Interactive visual cluster analysis is the most intuitive way for finding clustering patterns, validating algorithmic clustering results, understanding data clusters with domain knowledge, and refining cluster definitions. The most challenging step i

Hosting data query services in public clouds is an attractive solution for its great scalability and significant cost savings. However, data owners also have concerns on data privacy due to the lost control of the infrastructure. This demonstration shows a prototype for efficient and confidential range/kNN query services built on top of the random space perturbation (RASP) method. The RASP approach provides a privacy guarantee practical to the setting of cloud-based computing, while enabling much faster query processing compared to the encryption-based approach. This demonstration will allow users to more intuitively understand the technical merits of the RASP approach via interactive exploration of the visual interface.

With the wide deployment of public cloud computing infrastructures, using clouds to host data query services has become an appealing solution for the advantages on scalability and cost-saving. However, some data might be sensitive that the data owner does not want to move to the cloud unless the data confidentiality and query privacy are guaranteed. On the other hand, a secured query service should still provide efficient query processing and significantly reduce the in-house workload to fully realize the benefits of cloud computing. We propose the random space perturbation (RASP) data perturbation method to provide secure and efficient range query and kNN query services for protected data in the cloud. The RASP data perturbation method combines order preserving encryption, dimensionality expansion, random noise injection, and random projection, to provide strong resilience to attacks on the perturbed data and queries. It also preserves multidimensional ranges, which allows existing indexing techniques to be applied to speedup range query processing. The kNN-R algorithm is designed to work with the RASP range query algorithm to process the kNN queries. We have carefully analyzed the attacks on data and queries under a precisely defined threat model and realistic security assumptions. Extensive experiments have been conducted to show the advantages of this approach on efficiency and security.

Running MapReduce programs in the cloud introduces this unique problem: how to optimize resource provisioning to minimize the monetary cost or job finish time for a specific job? We study the whole process of MapReduce processing and build up a cost function that explicitly models the relationship among the time cost, the amount of input data, the available system resources (Map and Reduce slots), and the complexity of the Reduce function for the target MapReduce job. The model parameters can be learned from test runs. Based on this cost function, we can solve a number of decision problems, such as the optimal amount of resources that can minimize monetary cost within a job finish deadline, minimize time cost under a certain monetary budget, or find the optimal tradeoffs between time and monetary costs. Experimental results show that the proposed approach performs well on a number of sample MapReduce programs in both the in-house cluster and Amazon EC2. We also conducted a variance analysis on different components of the MapReduce workflow to show the possible sources of modeling error. Our optimization results show that with the proposed approach we can save a significant amount of time and money, compared to randomly selected settings.

With the development of sensor network, mobile computing, and web applications, data are now collected from many distributed sources to form big datasets. Such datasets can be hosted in the cloud to achieve economical processing and sharing. However, these data might be highly sensitive requiring secure storage and processing. We envision a cloud-based data storage and processing framework that enables users to economically and securely share and handle big datasets. Under this framework, we study the matrix-based data mining algorithms with a focus on the secure top-k eigenvector algorithm. Our approach uses an iterative processing model in which the authorized user interacts with the cloud to achieve the result. In this process, both the source matrix and the intermediate results keep confidential and the client-side incurs low costs. The security of this approach is guaranteed by using Paillier Encryption and a random perturbation technique. We carefully analyze its security under a cloud-specific threat model. Our experimental results show that the proposed method is scalable to big matrices while requiring low client-side costs.

Mining large data requires intensive computing resources and data mining expertise, which might not be available for many users. With the development of cloud computing and services computing, data mining tasks can now be moved to the cloud or outsourced to third parties to save costs. In this new paradigm, data and model confidentiality becomes the major concern to the data owner. Meanwhile, users are also concerned about the potential tradeoff among costs, model quality, and confidentiality. In this paper, we propose the PerturBoost framework to address the problems in confidential cloud or outsourced learning. PerturBoost combined with the random space perturbation (RASP) method that was also developed by us can effectively protect data confidentiality, model confidentiality, and model quality with low client-side costs. Based on the boosting framework, we develop a number of base learner algorithms that can learn linear classifiers from the RASP-perturbed data. This approach has been evaluated with public datasets. The result shows that the RASP-based PerturBoost can provide model accuracy very close to the classifiers trained with the original data and the AdaBoost method, with high confidentiality guarantee and acceptable costs.

This poster presents a preliminary study on the PerturBoost approach that aims to provide efficient and secure classifier learning in the cloud with both data and model privacy preserved.

Analysis of big data has become an important problem for many business and scientific applications, among which clustering and visualizing clusters in big data raise some unique challenges. This demonstration presents the CloudVista prototype system to address the problems with big data caused by using existing data reduction approaches. It promotes a whole-big-data visualization approach that preserves the details of clustering structure. The prototype system has several merits. (1) Its visualization model is naturally parallel, which guarantees the scalability. (2) The visual frame structure minimizes the data transferred between the cloud and the client. (3) The RandGen algorithm is used to achieve a good balance between interactivity and batch processing. (4) This approach is also designed to minimize the financial cost of interactive exploration in the cloud. The demonstration will highlight the problems with existing approaches and show the advantages of the CloudVista approach. The viewers will have the chance to play with the CloudVista prototype system and compare the visualization results generated with different approaches.

Running MapReduce programs in the public cloud introduces the important problem: how to optimize resource provisioning to minimize the financial charge for a specific job? In this paper, we study the whole process of MapReduce processing and build up a cost function that explicitly models the relationship between the amount of input data, the available system resources (Map and Reduce slots), and the complexity of the Reduce function for the target MapReduce job. The model parameters can be learned from test runs with a small number of nodes. Based on this cost model, we can solve a number of decision problems, such as the optimal amount of resources that can minimize the financial cost with a time deadline or minimize the time under certain financial budget. Experimental results show that this cost model performs well on tested MapReduce programs.

Range query is one of the most frequently used queries for online data analytics. Providing such a query service could be expensive for the data owner. With the development of services computing and cloud computing, it has become possible to outsource large databases to database service providers and let the providers maintain the range-query service. With outsourced services, the data owner can greatly reduce the cost in maintaining computing infrastructure and data-rich applications. However, the service provider, although honestly processing queries, may be curious about the hosted data and received queries. Most existing encryption based approaches require linear scan over the entire database, which is inappropriate for online data analytics on large databases. While a few encryption solutions are more focused on efficiency side, they are vulnerable to attackers equipped with certain prior knowledge. We propose the Random Space Encryption (RASP) approach that allows efficient range search with stronger attack resilience than existing efficiency-focused approaches. We use RASP to generate indexable auxiliary data that is resilient to prior knowledge enhanced attacks. Range queries are securely transformed to the encrypted data space and then efficiently processed with a two-stage processing algorithm. We thoroughly studied the potential attacks on the encrypted data and queries at three different levels of prior knowledge available to an attacker. Experimental results on synthetic and real datasets show that this encryption approach allows efficient processing of range queries with high resilience to attacks.

Machine-learned ranking functions have shown successes in Web search engines. With the increasing demands on developing effective ranking functions for different search domains, we have seen a big bottleneck, that is, the problem of insufficient labeled training data, which has significantly slowed the development and deployment of machine-learned ranking functions for different domains. There are two possible approaches to address this problem: (1) combining labeled training data from similar domains with the small target-domain labeled data for training or (2) using pairwise preference data extracted from user clickthrough log for the target domain for training. In this article, we propose a new approach called tree-based ranking function adaptation (Trada) to effectively utilize these data sources for training cross-domain ranking functions. Tree adaptation assumes that ranking functions are trained with the Stochastic Gradient Boosting Trees method—a gradient boosting method on regression trees. It takes such a ranking function from one domain and tunes its tree-based structure with a small amount of training data from the target domain. The unique features include (1) automatic identification of the part of the model that needs adjustment for the new domain and (2) appropriate weighing of training examples considering both local and global distributions. Based on a novel pairwise loss function that we developed for pairwise learning, the basic tree adaptation algorithm is also extended (Pairwise Trada) to utilize the pairwise preference data from the target domain to further improve the effectiveness of adaptation. Experiments are performed on real datasets to show that tree adaptation can provide better-quality ranking functions for a new domain than other methods.

Adapting to rank address the problem of insufficient domain-specific labeled training data in learning to rank. However, the initial study shows that adaptation is not always effective. In this paper, we investigate the relationship between the domain similarity and the effectiveness of domain adaptation with the help of two domain similarity measure: relevance correlation and sample distribution correlation.

Many machine learning problems involve changes in both feature distribution and label distribution, such as domain adaptation and learning drifting concepts from data streams. Correctly detecting, identifying, and understanding the changes of data distributions can help us properly select data sampl

In multiparty collaborative data mining, participants contribute their own data sets and hope to collaboratively mine a comprehensive model based on the pooled data set. How to efficiently mine a quality model without breaching each party's privacy is the major challenge. In this paper, we propose an approach based on geometric data perturbation and data mining service-oriented framework. The key problem of applying geometric data perturbation in multiparty collaborative mining is to securely unify multiple geometric perturbations that are preferred by different parties, respectively. We have developed three protocols for perturbation unification. Our approach has three unique features compared to the existing approaches: with geometric data perturbation, these protocols can work for many existing popular data mining algorithms, while most of other approaches are only designed for a particular mining algorithm; both the two major factors: data utility and privacy guarantee are well preserved, compared to other perturbation-based approaches; and two of the three proposed protocols also have great scalability in terms of the number of participants, while many existing cryptographic approaches consider only two or a few more participants. We also study different features of the three protocols and show the advantages of different protocols in experiments.

Machine Learned Ranking approaches have shown successes in web search engines. With the increasing demands on developing effective ranking functions for different search domains, we have seen a big bottleneck, i.e., the problem of insufficient training data, which has significantly limited the fast development and deployment of machine learned ranking functions for different web search domains. In this paper, we propose a new approach called tree based ranking function adaptation ("tree adaptation") to address this problem. Tree adaptation assumes that ranking functions are trained with regression-tree based modeling methods, such as Gradient Boosting Trees. It takes such a ranking function from one domain and tunes its tree-based structure with a small amount of training data from the target domain. The unique features include (1) it can automatically identify the part of model that needs adjustment for the new domain, (2) it can appropriately weight training examples considering both local and global distributions. Experiments are performed to show that tree adaptation can provide better-quality ranking functions for a new domain, compared to other modeling methods.

We present a general boosting method extending functional gradient boosting to optimize complex loss functions that are encountered in many machine learning problems. Our approach is based on optimization of quadratic upper bounds of the loss functions which allows us to present a rigorous convergence analysis of the algorithm. More importantly, this general framework enables us to use a standard regression base learner such as decision trees for fitting any loss function. We illustrate an application of the proposed method in learning ranking functions for Web search by combining both preference data and labeled data for training. We present experimental results for Web search using data from a commercial search engine that show significant improvements of our proposed methods over some existing methods.

No abstract available.

Data perturbation is a popular technique for privacy-preserving data mining. The major challenge of data perturbation is balancing privacy protection and data quality, which are normally considered as a pair of contradictive factors. We propose that selectively preserving only the task/model specific information in perturbation would improve the balance. Geometric data perturbation, consisting of random rotation perturbation, random translation perturbation, and noise addition, aims at preserving the important geometric properties of a multidimensional dataset, while providing better privacy guarantee for data classification modeling. The preliminary study has shown that random geometric perturbation can well preserve model accuracy for several popular classification models, including kernel methods, linear classifiers, and SVM classifiers, while it also revealed some security concerns to random geometric perturbation. In this paper, we address some potential attacks to random geometric perturbation and design several methods to reduce the threat of these attacks. Experimental study shows that the enhanced geometric perturbation can provide satisfactory privacy guarantee while still well preserving model accuracy for the discussed data classification models.

Effective ranking functions are an essential part of commercial search engines. We focus on developing a regression framework for learning ranking functions for improving relevance of search engines serving diverse streams of user queries. We explore supervised learning methodology from machine learning, and we distinguish two types of relevance judgments used as the training data: 1) absolute relevance judgments arising from explicit labeling of search results; and 2) relative relevance judgments extracted from user clickthroughs of search results or converted from the absolute relevance judgments. We propose a novel optimization framework emphasizing the use of relative relevance judgments. The main contribution is the development of an algorithm based on regression that can be applied to objective functions involving preference data, i.e., data indicating that a document is more relevant than another with respect to a query. Experimental results are carried out using data sets obtained from a commercial search engine. Our results show significant improvements of our proposed methods over some existing methods.

OBJECTIVE: A major problem faced in biomedical informatics involves how best to present information retrieval results. When a single query retrieves many results, simply showing them as a long list often provides poor overview. With a goal of presenting users with reduced sets of relevant citations, this study developed an approach that retrieved and organized MEDLINE citations into different topical groups and prioritized important citations in each group. DESIGN: A text mining system framework for automatic document clustering and ranking organized MEDLINE citations following simple PubMed queries. The system grouped the retrieved citations, ranked the citations in each cluster, and generated a set of keywords and MeSH terms to describe the common theme of each cluster. MEASUREMENTS: Several possible ranking functions were compared, including citation count per year (CCPY), citation count (CC), and journal impact factor (JIF). We evaluated this framework by identifying as "important" those articles selected by the Surgical Oncology Society. RESULTS: Our results showed that CCPY outperforms CC and JIF, i.e., CCPY better ranked important articles than did the others. Furthermore, our text clustering and knowledge extraction strategy grouped the retrieval results into informative clusters as revealed by the keywords and MeSH terms extracted from the documents in each cluster. CONCLUSIONS: The text mining system studied effectively integrated text clustering, text summarization, and text ranking and organized MEDLINE retrieval results into different topical groups.

It is widely recognized that developing efficient and fully automated algorithms for clustering large transactional datasets is a challenging problem. In this paper, we propose a fast, memory-efficient, and scalable clustering algorithm for analyzing transactional data. Our approach has three unique features. First, we use the concept of Weighted Coverage Density as a categorical similarity measure for efficient clustering of transactional datasets. The concept of weighted coverage density is intuitive and allows the weight of each item in a cluster to be changed dynamically according to the occurrences of items. Second, we develop two transactional data clustering specific evaluation metrics based on the concept of large transactional items and the coverage density respectively. Third, we implement the weighted coverage density clustering algorithm and the two clustering validation metrics using a fully automated transactional clustering framework, called SCALE (Sampling, Clustering structure Assessment, cLustering and domain-specific Evaluation). The SCALE framework is designed to combine the weighted coverage density measure for clustering over a sample dataset with self-configuring methods that can automatically tune the two important parameters of the clustering algorithms: (1) the candidates of the best number K of clusters; and (2) the application of two domain-specific cluster validity measures to find the best result from the set of clustering results. We have conducted experimental evaluation using both synthetic and real datasets and our results show that the weighted coverage density approach powered by the SCALE framework can efficiently generate high quality clustering results in a fully automated manner.

Analyzing clustering structures in data streams can provide critical information for making decision in realtime. In this paper, we present a framework for detecting the change of critical clustering structure in categorical data streams. The framework consists of the Hierarchical Entropy Tree structure (HE-Tree) and the extended ACE clustering algorithm. HE-Tree can efficiently capture the entropy property of the categorical data streams and allow us to draw precise clustering information from the data stream for high-quality BkPLots with the extended ACE algorithm.

With continued advances in communication network technology and sensing technology, there is astounding growth in the amount of data produced and made available through cyberspace. Efficient and high-quality clustering of large datasets continues to be one of the most important problems in large-scale data analysis. A commonly used methodology for cluster analysis on large datasets is the three-phase framework of sampling/summarization, iterative cluster analysis, and disk-labeling. There are three known problems with this framework which demand effective solutions. The first problem is how to effectively define and validate irregularly shaped clusters, especially in large datasets. Automated algorithms and statistical methods are typically not effective in handling these particular clusters. The second problem is how to effectively label the entire data on disk (disk-labeling) without introducing additional errors, including the solutions for dealing with outliers, irregular clusters, and cluster boundary extension. The third obstacle is the lack of research about issues related to effectively integrating the three phases. In this article, we describe iVIBRATE---an interactive visualization-based three-phase framework for clustering large datasets. The two main components of iVIBRATE are its VISTA visual cluster-rendering subsystem which invites human interplay into the large-scale iterative clustering process through interactive visualization, and its adaptive ClusterMap labeling subsystem which offers visualization-guided disk-labeling solutions that are effective in dealing with outliers, irregular clusters, and cluster boundary extension. Another important contribution of iVIBRATE development is the identification of the special issues presented in integrating the two components and the sampling approach into a coherent framework, as well as the solutions for improving the reliability of the framework and for minimizing the amount of errors generated within the cluster analysis process. We study the effectiveness of the iVIBRATE framework through a walkthrough example dataset of a million records and we experimentally evaluate the iVIBRATE approach using both real-life and synthetic datasets. Our results show that iVIBRATE can efficiently involve the user in the clustering process and generate high-quality clustering results for large datasets.

Data perturbation techniques are one of the most popular models for privacy preserving data mining (Agrawal and Srikant, 2000; Aggarwal and Yu, 2004). It is especially convenient for applications where the data owners need to export/publish the privacy-sensitive data. A data perturbation procedure can be simply described as follows. Before the data owner publishes the data, they randomly change the data in certain way to disguise the sensitive information while preserving the particular data property that is critical for building the data models. Several perturbation techniques have been proposed recently, among which the most typical ones are randomization approach (Agrawal and Srikant, 2000) and condensation approach (Aggarwal and Yu, 2004).

With the rapid increase of data in many areas, clustering on large datasets has become an important problem in data analysis. Since cluster is a highly iterative process, cluster on large datasets prefers short iteration on a relatively small representative set. Thus, a two-phase framework sampling/summarization - iterative cluster analysis is often applied in practice. Since the clustering result only labels the small representative set, there are problems with extending the result to the entire large dataset, which are almost ignored by the traditional clustering research. This extending is often named as labeling process. Labeling irregular shaped clusters, distinguishing outliers and extending cluster boundary are the main problems in this stage. We address these problems and propose a visualization-based approach to dealing with them precisely. This approach partially involves human into the process of defining and refining the structure ClusterMap. Based on this structure, the ClusterMap algorithm scans the large dataset to adapt the boundary extension and generate the cluster labels for the entire dataset. Experimental result shows that ClusterMap can preserve cluster quality considerably with low computational cost, compared to the distance-comparison-based labeling algorithms.

The automatic clustering algorithms are known to work well in dealing with clusters of regular shapes, e.g. compact spherical/elongated shapes, but may incur higher error rates when dealing with arbitrarily shaped clusters. Although some efforts have been devoted to addressing the problem of skewed datasets, the problem of handling clusters with irregular shapes is still in its infancy, especially in terms of dimensionality of the datasets and the precision of the clustering results considered. Not surprisingly, the statistical indices works ineffective in validating clusters of irregular shapes, too. We address the problem of clustering and validating arbitrarily shaped clusters with a visual framework (VISTA). The main idea of the VISTA approach is to capitalize on the power of visualization and interactive feedbacks to encourage domain experts to participate in the clustering revision and clustering validation process.

Clustering is a technique commonly used in scientific research. The task of clustering inevitably involves human participation - the clustering is not finished when the computer/algorithm finishes but the user has evaluated, understood and accepted the patterns. This defines a human involved "clustering-analysis/evaluation" iteration. Instead of neglecting this human involvement, we provide a visual framework (VISTA) with all power of algorithmic approaches (since their result can be visualized), and in addition we allow the user to steer/monitor/refine the clustering process with domain knowledge. The visual-rendering result also provides a precise pattern for fast post-processing.