인메모리 기반의 클러스터 환경에서 분산 병렬 SWRL 추론에 대한 연구

이완곤(Wan-Gon Lee),배석현(Seok-Hyun Bae),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2018 정보과학회논문지 Vol.45 No.3

Recently, there are many of studies on SWRL reasoning engine based on user-defined rules in a distributed environment using a large-scale ontology. Unlike the schema based axiom rules, efficient inference orders cannot be defined in SWRL rules. There is also a large volumet of network shuffled data produced by unnecessary iterative processes. To solve these problems, in this study, we propose a method that uses Map-Reduce algorithm and distributed in-memory framework to deduce multiple rules simultaneously and minimizes the volume data shuffling occurring between distributed machines in the cluster. For the experiment, we use WiseKB ontology composed of 200 million triples and 36 user-defined rules. We found that the proposed reasoner makes inferences in 16 minutes and is 2.7 times faster than previous reasoning systems that used LUBM benchmark dataset.

클라우드 컴퓨팅 환경에서의 대용량 RDFS 추론을 위한 분산 테이블 조인 기법

이완곤(Wan-Gon Lee),김제민(Je-Min Kim),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2014 정보과학회논문지 Vol.41 No.9

The Knowledge service system needs to infer a new knowledge from indicated knowledge to provide its effective service. Most of the Knowledge service system is expressed in terms of ontology. The volume of knowledge information in a real world is getting massive, so effective technique for massive data of ontology is drawing attention. This paper is to provide the method to infer massive data-ontology to the extent of RDFS, based on cloud computing environment, and evaluate its capability. RDFS inference suggested in this paper is focused on both the method applying MapReduce based on RDFS meta table, and the method of single use of cloud computing memory without using MapReduce under distributed file computing environment. Therefore, this paper explains basically the inference system structure of each technique, the meta table set-up according to RDFS inference rule, and the algorithm of inference strategy. In order to evaluate suggested method in this paper, we perform experiment with LUBM set which is formal data to evaluate ontology inference and search speed. In case LUBM6000, the RDFS inference technique based on meta table had required 13.75 minutes(inferring 1,042 triples per second) to conduct total inference, whereas the method applying the cloud computing memory had needed 7.24 minutes(inferring 1,979 triples per second) showing its speed twice faster.

분산 처리 환경에서 SWRL 규칙을 이용한 대용량 점증적 추론 방법

이완곤(Wan-Gon Lee),방성혁(Sung-Hyuk Bang),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2017 정보과학회논문지 Vol.44 No.4

As we enter a new era of Big Data, the amount of semantic data has rapidly increased. In order to derive meaningful information from this large semantic data, studies that utilize the SWRL(Semantic Web Rule Language) are being actively conducted. SWRL rules are based on data extracted from a user’s empirical knowledge. However, conventional reasoning systems developed on single machines cannot process large scale data. Similarly, multi-node based reasoning systems have performance degradation problems due to network shuffling. Therefore, this paper overcomes the limitations of existing systems and proposes more efficient distributed inference methods. It also introduces data partitioning strategies to minimize network shuffling. In addition, it describes a method for optimizing the incremental reasoning process through data selection and determining the rule order. In order to evaluate the proposed methods, the experiments were conducted using WiseKB consisting of 200 million triples with 83 user defined rules and the overall reasoning task was completed in 32.7 minutes. Also, the experiment results using LUBM bench datasets showed that our approach could perform reasoning twice as fast as MapReduce based reasoning systems.

분산 메모리 환경에서의 ABox 실체화 추론

이완곤(Wan-Gon Lee),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2015 정보과학회논문지 Vol.42 No.7

As the amount of knowledge information significantly increases, a lot of progress has been made in the studies focusing on how to reason large scale ontology effectively at the level of RDFS or OWL. These reasoning methods are divided into TBox classifications and ABox realizations. A TBox classification mainly deals with integrity and dependencies in schema, whereas an ABox realization mainly handles a variety of issues in instances. Therefore, the ABox realization is very important in practical applications. In this paper, we propose a realization method for analyzing the constraint of the specified class, so that the reasoning system automatically infers the classes to which instances belong. Unlike conventional methods that take advantage of the object oriented language based distributed file system, we propose a large scale ontology reasoning method using spark, which is a functional programming-based in-memory system. To verify the effectiveness of the proposed method, we used instances created from the Wine ontology by W3C(120 to 600 million triples). The proposed system processed the largest 600 million triples and generated 951 million triples in 51 minutes (696 K triple / sec) in our largest experiment.

신뢰 값 기반의 대용량 OWL Horst 온톨로지 추론

이완곤(Wan-Gon Lee),박현규(Hyun-Kyu Park),바트셀렘(Batselem Jagvaral),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2016 정보과학회논문지 Vol.43 No.5

Several machine learning techniques are able to automatically populate ontology data from web sources. Also the interest for large scale ontology reasoning is increasing. However, there is a problem leading to the speculative result to imply uncertainties. Hence, there is a need to consider the reliability problems of various data obtained from the web. Currently, large scale ontology reasoning methods based on the trust value is required because the inference-based reliability of quantitative ontology is insufficient. In this study, we proposed a large scale OWL Horst reasoning method based on a confidence value using spark, a distributed in-memory framework. It describes a method for integrating the confidence value of duplicated data. In addition, it explains a distributed parallel heuristic algorithm to solve the problem of degrading the performance of the inference. In order to evaluate the performance of reasoning methods based on the confidence value, the experiment was conducted using LUBM3000. The experiment results showed that our approach could perform reasoning twice faster than existing reasoning systems like WebPIE.

미디어 온톨로지의 시공간 정보 확장을 위한 분산 인메모리 기반의 대용량 RDFS 추론 및 질의 처리 엔진

이완곤(Wan-Gon Lee),이남기(Nam-Gee Lee),전명중(MyungJoong Jeon),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2016 정보과학회논문지 Vol.43 No.9

Providing a semantic knowledge system using media ontologies requires not only conventional axiom reasoning but also knowledge extension based on various types of reasoning. In particular, spatio-temporal information can be used in a variety of artificial intelligence applications and the importance of spatio-temporal reasoning and expression is continuously increasing. In this paper, we append the LOD data related to the public address system to large-scale media ontologies in order to utilize spatial inference in reasoning. We propose an RDFS/Spatial inference system by utilizing distributed memory-based framework for reasoning about large-scale ontologies annotated with spatial information. In addition, we describe a distributed spatio-temporal SPARQL parallel query processing method designed for large scale ontology data annotated with spatio-temporal information. In order to evaluate the performance of our system, we conducted experiments using LUBM and BSBM data sets for ontology reasoning and query processing benchmark.

부분 임베딩 기반의 지식 완성 기법

이완곤(Wan-Gon Lee),바트셀렘(Batselem Jagvaral),홍지훈(Ji-Hun Hong),최현영(Hyun-Young Choi),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2018 정보과학회논문지 Vol.45 No.11

Knowledge graphs are large networks that describe real world entities and their relationships with triples. Most of the knowledge graphs are far from being complete, and many previous studies have addressed this problem using low dimensional graph embeddings. Such methods assume that knowledge graphs are fixed and do not change. However, real-world knowledge graphs evolve at a rapid pace with the addition of new triples.Repeated retraining of embedding models for the entire graph is computationally expensive and impractical. In this paper, we propose a partial embedding method for partial completion of evolving knowledge graphs. Our method employs ontological axioms and contextual information to extract relations of interest and builds entity and relation embedding models based on instances of such relations. Our experiments demonstrated that the proposed partial embedding method can produce comparable results on knowledge graph completion with state-of-the-art methods while significantly reducing the computation time of entity and relation embeddings by 49%–90% for the Freebase and WiseKB datasets.

동적 분산병렬 하둡시스템 및 분산추론기에 응용한 서버가상화 빅데이터 플랫폼

송동호,신지애,인연진,이완곤,이강세,Song, Dong Ho,Shin, Ji Ae,In, Yean Jin,Lee, Wan Gon,Lee, Kang Se 한국데이터정보과학회 2015 한국데이터정보과학회지 Vol.26 No.5

시멘틱 웹 기술인 RDF 트리플로 표현된 지식을 추론 과정을 거치면 새로운 트리플들이 생성되어 나온다. 초기 입력된 수억개의 트리플로 구성된 빅데이터와 추가로 생성된 트리플 데이터를 바탕으로 질의응답과 같은 다양한 응용시스템이 만들어 진다. 이 추론기가 수행되는 과정에서 더 많은 컴퓨팅 리소스가 필요해 진다. 이 추가 컴퓨팅 리소스는 하부 클라우드 컴퓨팅의 리소스 풀로부터 공급받아 수행시간을 줄일 수 있다. 본 연구에서는 하둡을 이용하는 환경에서 지식의 크기에 따라 런타임에 동적으로 서버 컴퓨팅 노드를 증감 시키는 방법을 연구하였다. 상부는 응용계층이며, 중간부는 트리플들에 대한 분산병렬추론과 하부는 탄력적 하둡시스템 및 가상화 서버로 구성되는 계층적 모델을 제시한다. 이 시스템의 알고리즘과 시험성능의 결과를 분석한다. 하둡 상에 기 개발된 풍부한 응용소프트웨어들은 이 탄력적 하둡 시스템 상에서 수정 없이 보다 빨리 수행될 수 있는 장점이 있다. Inference process generates additional triples from knowledge represented in RDF triples of semantic web technology. Tens of million of triples as an initial big data and the additionally inferred triples become a knowledge base for applications such as QA(question&answer) system. The inference engine requires more computing resources to process the triples generated while inferencing. The additional computing resources supplied by underlying resource pool in cloud computing can shorten the execution time. This paper addresses an algorithm to allocate the number of computing nodes "elastically" at runtime on Hadoop, depending on the size of knowledge data fed. The model proposed in this paper is composed of the layered architecture: the top layer for applications, the middle layer for distributed parallel inference engine to process the triples, and lower layer for elastic Hadoop and server visualization. System algorithms and test data are analyzed and discussed in this paper. The model hast the benefit that rich legacy Hadoop applications can be run faster on this system without any modification.

Extracting Rules from Neural Networks with Continuous Attributes

Batselem Jagvaral(바트셀렘),Wan-Gon Lee(이완곤),Myung-joong Jeon(전명중),Hyun-Kyu Park(박현규),Young-Tack Park(박영택 ) Korean Institute of Information Scientists and Eng 2018 정보과학회논문지 Vol.45 No.1

Over the decades, neural networks have been successfully used in numerous applications from speech recognition to image classification. However, these neural networks cannot explain their results and one needs to know how and why a specific conclusion was drawn. Most studies focus on extracting binary rules from neural networks, which is often impractical to do, since data sets used for machine learning applications contain continuous values. To fill the gap, this paper presents an algorithm to extract logic rules from a trained neural network for data with continuous attributes. It uses hyperplane-based linear classifiers to extract rules with numeric values from trained weights between input and hidden layers and then combines these classifiers with binary rules learned from hidden and output layers to form non-linear classification rules. Experiments with different datasets show that the proposed approach can accurately extract logical rules for data with nonlinear continuous attributes.

신뢰값 기반 대용량 트리플 처리를 위한 스파크 환경에서의 RDFS 온톨로지 추론

박현규(Hyun-Kyu Park),이완곤(Wan-Gon Lee),바트셀렘(Batselem Jagvaral),박영택(Young-Tack Park) Korean Institute of Information Scientists and Eng 2016 정보과학회논문지 Vol.43 No.1

Recently, due to the development of the Internet and electronic devices, there has been an enormous increase in the amount of available knowledge and information. As this growth has proceeded, studies on large-scale ontological reasoning have been actively carried out. In general, a machine learning program or knowledge engineer measures and provides a degree of confidence for each triple in a large ontology. Yet, the collected ontology data contains specific uncertainty and reasoning such data can cause vagueness in reasoning results. In order to solve the uncertainty issue, we propose an RDFS reasoning approach that utilizes confidence values indicating degrees of uncertainty in the collected data. Unlike conventional reasoning approaches that have not taken into account data uncertainty, by using the in-memory based cluster computing framework Spark, our approach computes confidence values in the data inferred through RDFS-based reasoning by applying methods for uncertainty estimating. As a result, the computed confidence values represent the uncertainty in the inferred data. To evaluate our approach, ontology reasoning was carried out over the LUBM standard benchmark data set with addition arbitrary confidence values to ontology triples. Experimental results indicated that the proposed system is capable of running over the largest data set LUBM3000 in 1179 seconds inferring 350K triples.