Efficient support for querying large-scale resource description framework (RDF) triples plays an important role in semantic web data management. This paper presents an efficient RDF query engine to evaluate SPARQL queries, where the inverted index structure is employed for indexing the RDF triples. A set of operators on the inverted index was developed for query optimization and evaluation. Then a main-tree-shaped optimization algorithm was developed that transforms a SPARQL query graph into the optimal query plan by effectively reducing the search space to determine the optimal joining order. The optimization collects a set of RDF statistics for estimating the execution cost of the query plan. Finally the optimal query plan is evaluated using the defined operators for answering the given SPARQL query. Extensive tests were conducted on both synthetic and real datasets containing up to 100 million triples to evaluate this approach with the results showing that this approach can answer most queries within 1 s and is extremely efficient and scalable in comparison with previous best state-of-the-art RDF stores.
Wikipedia, a killer application in Web 2.0, has embraced the power of collaborative editing to harness collective intelligence. It features many attractive characteristics, like entity-based link graph, abundant categorization and semi-structured layout, and can...
Recently, search engine companies like Google and Baidu are building their own knowledge graphs to empower the next generation of Web search. Due to the success of knowledge graphs in search, customers from vertical sectors are eager to embrace KG related technologies to develop domain specific semantic platforms or applications. However, they lack skills or tools to achieve the goal. In this paper, we present an integrated tool VKGBuilder to help users manage the life cycle of knowledge graphs. We will describe three modules of VKGBuilder in detail which construct, store, search and explore knowledge graphs in vertical domains. In addition, we will demonstrate the capability and usability of VKGBuilder via a real-world use case in the library industry.
Compared with plain-text resources, the ones in “semi-semantic” web sites, such as Wikipedia, contain high-level semantic information which will benefit various automatically annotating tasks on themself. In this paper, we propose a “collaborative...
Adopting keyword query interface to semantic search on RDF data can help users keep away from learning the SPARQL query syntax and understanding the complex and fast evolving data schema. The existing approaches are divided into two categories: instance-based approaches and schema-based approaches. The instance-based approaches relying on the original RDF graph can generate precise answers but take a long processing time. In contrast, the schema-based approaches relying on the reduced summary graph require much less processing time but cannot always generate correct answers. In this paper, we propose a novel approach based on a hybrid graph which can achieve significant improvements on processing time with a limited accuracy drop compared with instance-based approaches, and meanwhile, can achieve promising accuracy gains at an affordable time cost compared with schema-based approaches.
The Web of Data keeps growing rapidly. However, the full exploitation of this large amount of structured data faces numerous challenges like usability, scalability, imprecise information needs and data change. We present Semplore, an IR-based system that aims at addressing these issues. Semplore supports intuitive faceted search and complex queries both on text and structured data. It combines imprecise keyword search and precise structured query in a unified ranking scheme. Scalable query processing is supported by leveraging inverted indexes traditionally used in IR systems. This is combined with a novel block-based index structure to support efficient index update when data changes. The experimental results show that Semplore is an efficient and effective system for searching the Web of Data and can be used as a basic infrastructure for Web-scale Semantic Web search engines.
DBpedia and YAGO are the two main data sources serving as the hub of Linking Open Data (LOD), and they both contain Chinese data. Zhishi.me and SSCO extract Chinese knowledge from Wikipedia and other Chinese Encyclopedic Web sites like Baidu-Baike and Hudong-Baike....
Digital photo album softwares like iPhoto have enjoyed great popularity for years. These years, online photo album services (e.g., Flickr and Picasa) have been becoming more and more popular with the development of social Web. In this paper, we present a...
DeepSeek, a Chinese artificial intelligence (AI) startup, has released their V3 and R1 series models, which attracted global attention due to their low cost, hi
Schema-level knowledge is important for different semantic applications, such as reasoning, data integration and question answering. Compared with billions of triples describing millions of instances, current Linking Open Data has only a limited number of triples representing schema-level knowledge. To facilitate multilingual schema-level knowledge mining, we propose a general approach to learn Linked Open Schema (LOS) in different languages from social Web sites, which contain rich sources (i.e. taxonomies composed of categories and folksonomies consisting of tags) for mining large-scale schema-level knowledge. The core part of the proposed approach is a semi-supervised learning method integrating rules to capture equal, subClassOf and relate relations among the collected categories and tags. We respectively apply the proposed approach to the selected English social Web sites and the Chinese ones, resulting in an English LOS and a Chinese LOS. We publish the English LOS and the Chinese one as open data on the Web with three access levels, i.e. data dump, lookup service and SPARQL endpoint. Experimental results show the high accuracy of the relations in the English LOS and the Chinese one. Compared with DBpedia, Yago, BabelNet, and Freebase, both the English LOS and the Chinese one not only have large-scale concepts, but also contain the largest number of subClassOf relations.