Heterogeneous behavioral data provides comprehensive insights into user intentions and decision-making patterns. Contemporary multi-behavior recommendation models, which leverage such data to infer user preferences, typically capture high-order collaborative signals through graph neural networks on a multi-behavior heterogeneous graph or multiple behavior-specific subgraphs. However, auxiliary behaviors (e.g., view, cart) inherently contain noise that can mislead target behavior (e.g., purchase) prediction, and the incorporation of high-order collaborative signals further amplify such noise. Moreover, these approaches fail to adequately explore cross-behavior item dependencies, leading to inadequate modeling of dependencies across heterogeneous behaviors. To address these limitations, we propose Cross-behavior Item DEpendency modeling for multi-behavior Recommendation (CIDER) , a novel framework that explicitly models item dependencies across multiple types of behaviors for target behavior prediction (e.g., purchase). Specifically, our framework introduces the Hierarchical Behavior Sequence (HBS) , a data structure to systematically organize multi-behavior user–item interactions. Based on the HBS, we design a Cross-behavior Item Dependency Modeling (CIDM) module coupled with a multi-behavior cascading learning scheme to capture item-level dependencies. To enhance the robustness of the representations learned from the CIDM module, we develop an HBS-based denoising module that filters out noise inherent in auxiliary behaviors. Empirical evaluation on three benchmark datasets demonstrates the effectiveness of our model in harnessing multi-behavior data. The implementation is publicly available at https://github.com/SunJianier/CIDER .

In-memory databases (IMDBs) are gaining increasing popularity in big data applications, where clients commit updates intensively. Specifically, it is necessary for IMDBs to have efficient snapshot performance to support certain special applications (e.g., consistent checkpoint, HTAP). Formally, the in-memory consistent snapshot problem refers to taking an in-memory consistent time-in-point snapshot with the constraints that 1) clients can read the latest data items and 2) any data item in the snapshot should not be overwritten. Various snapshot algorithms have been proposed in academia to trade off throughput and latency, but industrial IMDBs such as Redis adhere to the simple fork algorithm. To understand this phenomenon, we conduct comprehensive performance evaluations on mainstream snapshot algorithms. Surprisingly, we observe that the simple fork algorithm indeed outperforms the state-of-the-arts in update-intensive workload scenarios. On this basis, we identify the drawbacks of existing research and propose two lightweight improvements. Extensive evaluations on synthetic data and Redis show that our lightweight improvements yield better performance than fork, the current industrial standard, and the representative snapshot algorithms from academia. Finally, we have opensourced the implementation of all the above snapshot algorithms so that practitioners are able to benchmark the performance of each algorithm and select proper methods for different application scenarios.

In-memory databases (IMDBs) are gaining increasing popularity in big data applications, where clients commit updates intensively. Consistent snapshot is a key step in backup and recovery of IMDBs, thus an important factor for system performance of IMDBs. Formally, the in-memory consistent snapshot problem refers to taking an in-memory consistent time-in-point snapshot with the constraints that 1) clients can read the latest data items, and 2) any data item in the snapshot should not be overwritten. Various snapshot algorithms have been proposed in the academia to trade off throughput and latency, yet industrial IMDBs such as Redis still stick to the simple fork algorithm. As an understanding of this phenomenon, we conduct comprehensive performance evaluations on mainstream snapshot algorithms. Surprisingly, we observe that the simple fork algorithm indeed outperforms the state-of-the-arts in update-intensive workload scenarios. On this basis, we identify the drawbacks of existing research and propose two lightweight improvements. Extensive evaluations on synthetic data and Redis show that our lightweight improvements yield better performance than fork, the current industrial standard, and the representative snapshot algorithms from the academia. Finally, we have opensourced the implementation of all the above snapshot algorithms to facilitate practitioners to benchmark the performance of each algorithm and select proper methods for different application scenarios.

In this demonstration, we present a system that recommends to the user the locations and activities she/he might be interested in according to history GPS trajectories and public places of interest (POI) data. Its innovation lies in the acceptable performance of recommendations in cases where no user comments on activity types are available. Such situations are more realistic considering the restrictions on mobile devices' abilities, users' privacies, or business secret. For this purpose, we first extract stay points according to uses' trajectories, and label them with the top-k common activities which have the most possibility in terms of the POI dataset. Then, by taking stay points as observations, and activities as hidden states, a Hidden Markov model is built to learn the transfer possibilities between activities and the generation probabilities between activities and stay points. Finally, with the obtained model, our system can perform two types of recommendation, i.e. the history based recommendation and the similarity based recommendation. The results of former type are those stay points from user's own history positions. While, the latter one conducts collaborative filtering by taking history based recommendation results from similar users. The demonstration shows the running effects of the implemented prototype system, in which the Microsoft GeoLife trajectories dataset and the "DianPing.com" POI dataset were loaded. The preliminary experimental results demonstrate the feasibility.

Finding all justifications of an OWL entailment is an important reasoning service for explaining logical inconsistencies. In this paper, we consider finding all justifications of an entailment in OWL pD* fragment, which is a fragment of OWL that makes possible decidable rule extensions of OWL. We first propose a novel approach to find all justifications of OWL pD* entailments using TMS and show the complexity of this approach. This approach is limited by the hardware capabilities of standalone systems. In order to improve its scalability to handle large scale semantic data, we optimize the proposed approach by exploiting the MapReduce technology. We implement our approach and the optimization, and do experiments on synthetic and real world data sets. Evaluation results show that our approach has the ability to scale to more than one billion triples.

Falconer is a semantic Web search engine enhanced SIOC (Semantically-Interlinked Online Communities) application, which is designed to demonstrate the ability of accelerating the creation and reuse process of semantic Web data with easy-to-use user interfaces. In this process, semantic Web search engines feed existing semantic data into the SIOC framework, where new semantic data are composed by the community and indexed again by those search engines. Compared to existing social (semantic) Web applications, Falconer inherently conforms to SIOC specification. It provides semantic search engine based user registration suggestion, friends auto-discovery, and semantic annotation for forum post content. Another distinctive feature is that it enables users to subscribe any resource having a URI as the topic they are interested in. The relationships among users, topics, and posts are further visualized for analyzing the topic trends in the community. As all semantic data are formatted in RDF and RDFa, they can be queried with SPARQL query language.