著者

芦川 将之 川村 隆浩 大須賀 昭彦

出版者

The Japanese Society for Artificial Intelligence

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.29, no.6, pp.503-515, 2014

被引用文献数

2

---

Open Crowdsourcing platforms like Amazon Mechanical Turk provide an attractive solution for process of high volume tasks with low costs. However problems of quality control is still of major interest. In this paper, we design a private crowdsourcing system, where we can devise methods for the quality control. For the quality control, we introduce four worker selection methods, each of which we call preprocessing filtering, real-time filtering, post processing filtering, and guess processing filtering. These methods include a novel approach, which utilizes a collaborative filtering technique in addition to a basic approach of initial training or gold standard data. For an use case, we have built a very large dictionary, which is necessary for Large Vocabulary Continuous Speech Recognition and Text-to-Speech. We show how the system yields high quality results for some difficult tasks of word extraction, part-of-speech tagging, and pronunciation prediction to build a large dictionary.

著者

笠井 俊信 永野 和男 溝口 理一郎

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.30, no.3, pp.570-584, 2015-05-01 (Released:2015-05-01)

参考文献数

22

---

In order to facilitate learners' knowledge refinement process, it is effective to let them externalize their knowledge. However, in a domain of the instructional design in which existence of knowledge and its necessity are not sufficiently articulated or recognized, it is not easy for teachers who are also learners of how to externalize their knowledge. In this study, we have built a system called ``FIMA-Light'' which uncovers knowledge that teachers must have applied in their lesson plans from global to local viewpoints instead of them. FIMA-Light makes use of the OMNIBUS ontology which describes various instructional knowledge for attaining educational goals extracted from instructional/ learning theories. And, FIMA-Light automatically generates what we call I_L event decomposition trees by interpreting a given lesson plan based on the OMNIBUS ontology. Then, FIMA-Light facilitates teachers' deep reflection and helps them to refine their lesson plans by providing them with decomposition trees. We report some results of an experiment carried out for evaluation of the quality and the effectiveness of I_L event decomposition trees.

著者

金 英子 松尾 豊 石塚 満

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.22, no.1, pp.48-57, 2007 (Released:2007-01-05)

参考文献数

28

被引用文献数

3 6

---

Social relation plays an important role in a real community. Interaction patterns reveal relations among actors (such as persons, groups, companies), which can be merged into valuable information as a network structure. In this paper, we propose a new approach to extract inter-business relationship from the Web. Extraction of relation between a pair of companies is realized by using a search engine and text processing. Since names of companies co-appear coincidentaly on the Web, we propose an advanced algorithm which is characterized by addition of keywords (or we call relation words) to a query. The relation words are obtained from either an annotated corpus or the Web. We show some examples and comprehensive evaluations on our approach.

著者

宮崎 和光 坪井 創吾 小林 重信

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.16, no.2, pp.185-192, 2001 (Released:2002-02-28)

参考文献数

10

被引用文献数

1 7

---

Reinforcement learning is a kind of machine learning. It aims to adapt an agent to a given environment with a clue to rewards. In general, the purpose of reinforcement learning system is to acquire an optimum policy that can maximize expected reward per an action. However, it is not always important for any environment. Especially, if we apply reinforcement learning system to engineering, environments, we expect the agent to avoid all penalties. In Markov Decision Processes, a pair of a sensory input and an action is called rule. We call a rule penalty if and only if it has a penalty or it can transit to a penalty state where it does not contribute to get any reward. After suppressing all penalty rules, we aim to make a rational policy whose expected reward per an action is larger than zero. In this paper, we propose a suppressing penalty algorithm that can suppress any penalty and get a reward constantly. By applying the algorithm to the tick-tack-toe, its effectiveness is shown.

著者

谷口 忠大 椹木 哲夫

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.19, no.6, pp.493-501, 2004 (Released:2004-09-03)

参考文献数

13

被引用文献数

2 3

---

In this paper, a new machine-learning method, called Dual-Schemata model, is presented. Dual-Schemata model is a kind of self-organizational machine learning methods for an autonomous robot interacting with an unknown dynamical environment. This is based on Piaget's Schema model, that is a classical psychological model to explain memory and cognitive development of human beings. Our Dual-Schemata model is developed as a computational model of Piaget's Schema model, especially focusing on sensori-motor developing period. This developmental process is characterized by a couple of two mutually-interacting dynamics; one is a dynamics formed by assimilation and accommodation, and the other dynamics is formed by equilibration and differentiation. By these dynamics schema system enables an agent to act well in a real world. This schema's differentiation process corresponds to a symbol formation process occurring within an autonomous agent when it interacts with an unknown, dynamically changing environment. Experiment results obtained from an autonomous facial robot in which our model is embedded are presented; an autonomous facial robot becomes able to chase a ball moving in various ways without any rewards nor teaching signals from outside. Moreover, emergence of concepts on the target movements within a robot is shown and discussed in terms of fuzzy logics on set-subset inclusive relationships.

著者

大武 美保子

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.24, no.2, pp.295-302, 2009 (Released:2009-02-19)

参考文献数

26

被引用文献数

3 4

---

This paper proposes multiscale service design method through the development of support service for prevention and recovery from dementia towards science of lethe. Proposed multiscale service model consists of tool, event, human, network, style and rule. Service elements at different scales are developed according to the model. Firstly, the author proposes and practices coimagination method as an ``event'', which is expected to prevent the progress of cognitive impairment. Coimagination support system was developed as a ``tool''. Experimental results suggest the effective activation of episodic memory, division of attention, and planning function of participants by the measurement of cognitive activities during the coimagination. Then, Fonobono Research Institute was established as a ''network'' for ``human'' who studies coimagination, which is a multisector research organization including elderly people living around Kashiwa city, companies including instrument and welfare companies, Kashiwa city and Chiba prefecture, researchers of the University of Tokyo. The institute proposes and realizes lifelong research as a novel life ``style'' for elderly people, and discusses life with two rounds as an innovative ``rule'' for social system of aged society.

著者

桑原 教彰 桑原 和宏 安部 伸治 須佐見 憲史 安田 清

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.20, no.6, pp.396-405, 2005 (Released:2005-09-08)

参考文献数

22

被引用文献数

1 4

---

Providing good home-based care to people with dementia is becoming an important issue as the size of the elderly population increases. One of the main problems in providing such care is that it must be constantly provided without interruption, and this puts a great burden on caregivers, who are often family members. Networked Interaction Therapy is the name we call our methods designed to relieve the stress of people suffering from dementia as well as that of their family members. This therapy aims to provide a system that interacts with people with dementia by utilizing various engaging stimuli. One such stimulus is a reminiscence video created from old photo albums, which is a promising way to hold a dementia sufferer's attention for a long time. In this paper, we present an authoring tool to assist in the production of a reminiscence video by using photo annotations. We conducted interviews with several video creators on how they used photo annotations such as date, title and subject of photos when they produced the reminiscence videos. According to the creators' comments, we have defined an ontology for representing the creators' knowledge of how to add visual effects to a reminiscence video. Subsequently, we developed an authoring tool that automatically produces a reminiscence video from the annotated photos. Subjective evaluation of the quality of reminiscence videos produced with our tool indicates that they give impressions similar to those produced by creators using conventional video editing software. The effectiveness of presenting such a video to people with dementia is also discussed.

著者

山内 翔 川村 秀憲 鈴木 恵二

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.30, no.1, pp.1-11, 2015-01-01 (Released:2015-01-06)

参考文献数

19

被引用文献数

2 1

---

The main feature that keeps states and structures stable can be seen in living organisms. This adjusting and adaptive feature is called homeostasis. This integrated adaptive feature is achieved by the cooperation of organs in living organisms. Living organisms in nature act dynamically due to this feature. Highly adaptive behavior caused by this feature is also observed in simple living organisms that have no neural circuits such as amoebas. In amoeba case, each cell acts as an oscillator and such behavior is explicable as synchronization phenomena of oscillators. Based on these facts, a method of control to generate homeostasis in robotic systems is proposed by assuming a robot system is an aggregation of oscillators in this paper. When a robot system is assumed as an aggregation of oscillators, a robot system tries to keep the value of the specific function that indicate its uncomfortable level small the whole time. To keep such function value small, a robot system stabilize the relationship between oscillators when its value is small and reconstruct the relationship between oscillators when its value is large. This behavior is also explicable as synchronization phenomena of oscillators. A redundant robot arm is made to confirm the effect of this control method to generate homeostatic behaviors in robotic systems.

著者

小川 泰右 池田 満 鈴木 斎王 荒木 賢二

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.30, no.1, pp.37-46, 2015-01-01 (Released:2015-01-06)

参考文献数

16

---

PROBLEM is a key concept used in sharing intentions of medical services among health professionals belonging to different domains. PROBLEMs represent the necessity for medical services from each domain. PROBLEMs serve as a reference point for unifying multiple domain knowledge, when health professional team designs services. However, there is confusion on sharing intentions of the medical services using PROBLEMs. The confusion arose from the ambiguity of the role which the PROBLEMs are playing on intention expressions. Hence, the authors developed a media equipped with a function which specifies roles of PROBLEMs, and tried to control of this confusion. The result of the trial use suggests that the media suppresses the confusion and prompts users to externalize intentions of medical services.

著者

高丸 圭一 内田 ゆず 乙武 北斗 木村 泰知

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.30, no.1, pp.306-318, 2015-01-06 (Released:2015-01-06)

参考文献数

25

被引用文献数

2

---

An onomatopoeia is a useful linguistic expression to describe sounds, conditions, degrees and so on. It is said Japanese is rich in onomatopoeic expressions. They are frequently used in daily conversations. The meaning and surface structure of an onomatopoeia varies diachronically. There seem to be regional variations in usage of onomatopoeias. It is necessary to investigate the actual condition of onomatopoeia quantitatively in order to apply onomatopoeias into artificial intelligence. This paper studies practical usages of onomatopoeias in spoken modern Japanese language. To explore Japanese onomatopoeias nowadays, we investigate regional assembly minutes collected from all areas in Japan. The corpus of regional assembly minutes, which has about 300 million words, is the target of the investigation of this study. The minutes of Japanese regional assemblies contain all transcriptions of the utterances in the assemblies. This corpus is suitable for our research since attributes of the speakers are clear and speakers are distributed nation-wide. The first research is about total frequency and regional distribution of onomatopoeias. The onomatopoeias, which represent a request for a promotion of policy, e.g., ``shikkari'', ``dondon'', are used at high frequency in regional assemblies. There are no remarkable regional differences in frequencies of these onomatopoeias though western Japan has slight higher frequency. The second research is about the meaning of the onomatopoeias. Most of onomatopoeias are polysemous. The meaning of the onomatopoeia differs by context. The authors have manually checked through 10,827 sentences, which contain 153 kinds of onomatopoeia, and then classified the meaning of each onomatopoeic expression. We analyzed for the following subjects: i) ambiguity of onomatopoeic expression, ii) regional differences in meaning, iii) new meanings in modern spoken language, iv) special usage in assemblies, and v) onomatopoeias in the named entities. The third research is about false extraction of onomatopoeias in the morphological analysis. The extraction errors are analyzed from the viewpoint of surface structure and appearance position. In terms of surface structure, it is clear that the word length of an onomatopoeic expression, which has highly false extraction, is shorter. The onomatopoeic expressions, which end with special morae, namely moraic obstruent, moraic nasal and long vowel, have a higher rate of false extraction. In terms of appearance position, dialectal grammar is the main factor causing false extraction. About 25% of false extraction is found in the sentence-closing particles in dialectal grammar. The result of quantitative analysis of the onomatopoeia in modern spoken Japanese language serves as the basic data which contributes to engineering. The results of the analysis in our research are exhibited through the WWW. It is hoped that results will contribute broadly to the practical use of onomatopoeia in the engineering field.

著者

永田 裕一

出版者

人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.22, no.5, pp.542-552, 2007

被引用文献数

3

---

We propose an genetic algorithm (GA) that applies to the traveling salesman problem (TSP). The GA uses edge assembly crossover (EAX), which is known to be effective for solving the TSP. We first propose a fast implementation of a localized EAX where localized edge exchanges are used in the EAX procedure. We also propose a selection model with an effective combination of the localized EAX that can maintain population diversity at negligible computational costs. Edge entropy measure is used to evaluate population diversity. We demonstrate that the proposed GA is comparable to state-of-the-art heuristics for the TSP. Especially, the GA is superior to them on large instances more than 10,000 cities. For example, the GA found an optimal solution of brd14051 (14,051 cities instance) with a reasonable computational cost. The results are quite impressive because the GA does not use Lin-Kernighan local search (LKLS) even though almost all existing state-of-the-art heuristics for the TSP based on LKLS and its variants.

著者

千葉 和也 大和田 勇人 溝口 文雄

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.16, no.1, pp.156-163, 2001 (Released:2002-02-28)

参考文献数

15

被引用文献数

1 2 1

---

In this paper, we apply Inductive Logic Programming (ILP) to acquire graphic design knowledge. Acquiring design knowledge is a challenging task because such knowledge is complex and vast. We thus focus on principles of layout and constraints that layouts must satisfy to realize automatic layout generation. Although we do not have negative examples in this case, we can generate them randomly by considering that a page with just one element moved is always wrong. Our nonmonotonic learning method introduces a new predicate for exceptions. In our method, the ILP algorithm is executed twice, exchanging positive and negative examples. From our experiments using magazine advertisements, we obtained rules characterizing good layouts and containing relationships between elements. Moreover, the experiments show that our method can learn more accurate rules than normal ILP can.

著者

高橋 勇 小西 達裕 伊東 幸宏

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.16, no.1, pp.63-73, 2001 (Released:2002-02-28)

参考文献数

19

被引用文献数

2 1

---

In this paper, we discuss a planning and plan recognition approach to generate advice in a Micro- World. A Micro-World should be able to guide a learner who is in impasse. When a learner meets some trouble, a Micro-World should guide the learner by giving some advices. In order to generate appropriate advice, it should have an ability to construct a correct plan to achieve the learner’s goal, and to recognize the learner’s plan by observing the learner’s actions. Therefore we discuss the ability of planning and plan recognition in a Micro-World. We point out some problems concerning to unobservable actions and bad effectual actions, and propose methods to solve the problems. Then we introduce our experimental system. We take chemistry as our domain subject and the system can let a learner learn a chemical experiment with acid-base reactions.

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.24, no.6, pp.579-579, 2009 (Released:2009-10-22)

---

Vol.24, No.6 に掲載の論文のページ数に誤りがありました.( )内に正しいページ数を記します.

著者

藤原 浩司 兼岩 憲

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.29, no.4, pp.364-374, 2014-07-01 (Released:2014-06-18)

参考文献数

21

---

As one of the core technologies of the Semantic Web, the RDF data model enables us to represent machine-readable metadata about Web resources. SPARQL is the standard query language for answering queries from RDF data. In order to support SPARQL in practice, it is important to access such metadata quickly from large scale RDF data stores, such as Gene Ontology and DBpedia. In this paper, we present an algorithm that decides the solve order of an inputed query. We formalize the search space reduction of the connected variables occurring in a query and establish the costs of different query patterns. In particular, we consider selecting one of the various orders of elements in each query that results in less computation for searching and reasoning steps, i.e., matching a subgraph of a complex RDF graph. Using the algorithm, we implement an efficient query system with a RDF store (called NodeStore) for large-scale RDF data. In the RDF store, an indexed data structure of RDF graphs is well constructed for optimizing RDF data processing, e.g., finding a set of RDF triples including a common resource. For the evaluation of deciding the solve order of a query, we show some experimental results for our query system NodeStore and the Jena framework using a LUBM dataset (a benchmarking framework for semantic repositories).

著者

込山 悠介 番野 雅城 鑓水 優行 加藤 文彦 大向 一輝 武田 英明 清水 謙多郎

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.29, no.4, pp.356-363, 2014-07-01 (Released:2014-06-18)

参考文献数

12

---

Researchers of agriculture, life science and drug design of the need to acquire information that combines two or more life science databases for problem solving. Semantic Web technologies are already necessary for data integration between those databases. This study introduces a technique of utilizing RDF (Resource Description Framework) and OWL (Web Ontology Language) as a data set for development of a machine learning predictor of interactomics. Also, for SPARQL (SPARQL Protocol and RDF Query Language) we sketched the implementing method of interactomics LOD (Linked Open Data) in the graph database. Interactomics LOD has included the pairs of protein--protein interactions of tyrosine kinase, the pairs of amino acid residues of sugar (carbohydrate) binding proteins, and cross-reference information of the protein chain among an entry of major bioscience databases since 2013. Finally, we designed three RDF schema models and made access possible using AllegroGraph 4.11 and Virtuoso 7. The number of total triples was 1,824,859,745 in these databases. It could be combined with public LOD of the life science domain of 28,529,064,366 triples and was able to be searched. We showed that it was realistic to deal with large-scale LOD on a comparatively small budget by this research. The cost cut by LOD decreased not only expense but development time. Especially RDF-SIFTS (Structure Integration with Function, Taxonomy and Sequence) that is an aggregate of 10 small LOD was constructed in the short period of BioHackathon 2013 or was developed in one week. We could say that we can obtain quickly a data set required for the machine learning of interactomics by using LOD. We set up the interactomics LOD for application development as a database. SPARQL endpoints of these databases are exhibited on the portal site UTProt (The University of Tokyo Protein, http://utprot.net).

著者

小嵜 耕平 新保 仁 小町 守 松本 裕治

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.28, no.4, pp.400-408, 2013 (Released:2013-06-20)

参考文献数

30

---

Graph construction is an important step in graph-based semi-supervised classification. While the k-nearest neighbor graphs have been the de facto standard method of graph construction, this paper advocates using the less well-known mutual k-nearest neighbor graphs for high-dimensional natural language data. To evaluate the quality of the graphs apart from classification algortihms, we measure the assortativity of graphs. In addition, to compare the performance of these two graph construction methods, we run semi-supervised classification methods on both graphs in word sense disambiguation and document classification tasks. The experimental results show that the mutual k-nearest neighbor graphs, if combined with maximum spanning trees, consistently outperform the k-nearest neighbor graphs. We attribute better performance of the mutual k-nearest neighbor graph to its being more resistive to making hub vertices. The mutual k-nearest neighbor graphs also perform equally well or even better in comparison to the state-of-the-art b-matching graph construction, despite their lower computational complexity.

著者

長井 拓馬 兼岩 憲

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.29, no.3, pp.343-355, 2014-05-01 (Released:2014-06-05)

参考文献数

23

---

In this paper, we propose an algorithm for ALCH(D) concept learning from RDF data using minimal model reasoning. This algorithm generates concept expressions in the Description Logic ALCH(D) by giving background knowledge and positive and negative examples in the RDF form. Our method can be widely applied to RDF data on the Web, as background knowledge. An advantage of the method for RDF data is that reasoning on RDF graphs is tractable compared to logical reasoning for OWL data. We solve the problem that RDF data cannot be directly applied to the concept learning due to its less expressive power, speci.cally, the lack of negative expressions. In order to construct expressive ALCH(D) concepts from less expressive RDF data in the concept learning, we introduce (nonmonotonic) inference rules based on minimal model reasoning which derive implicit subclass and subproperty relations from the background knowledge in the RDF form. We prove the soundness, completeness and decidability of the nonmonotonic RDF reasoning in the minimal Herbrand models for RDF graphs. The process of concept learning is divided in two parts: (i) concept generation and (ii) concept evaluation. In the concept generation, minimal model reasoning enables us to derive complex concepts consisting of negation, conjunction, disjunction and quanti.ers and to exclude inconsistent concepts. In the concept evaluation, we evaluate hypothesis concepts with class and property hierarchies where minimal model reasoning is used for expressing more speci.c concepts as the answer for learning. We implement a system that learns some ALCH(D) concepts describing the features of given examples.

著者

中辻 真 藤原 靖宏 内山 俊郎 戸田 浩之

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.28, no.6, pp.457-467, 2013-11-01 (Released:2013-10-01)

参考文献数

33

被引用文献数

1

---

Tracking user interests over time is important for making accurate recommendations. However, the widely-used time-decay-based approach worsens the sparsity problem because it deemphasizes old item transactions. We introduce two ideas to solve the sparsity problem. First, we divide the users’ transactions into epochs i.e. time periods, and identify epochs that are dominated by interests similar to the current interests of the active user. Thus, it can eliminate dissimilar transactions while making use of similar transactions that exist in prior epochs. Second, we use a taxonomy of items to model user item transactions in each epoch. This well captures the interests of users in each epoch even if there are few transactions. It suits the situations in which the items transacted by users dynamically change over time; the semantics behind classes do not change so often while individual items often appear and disappear. Fortunately, many taxonomies are now available on the web because of the spread of the Linked Open Data vision. We can now use those to understand dynamic user interests semantically. We evaluate our method using a dataset, a music listening history, extracted from users’ tweets and one containing a restaurant visit history gathered from a gourmet guide site. The results show that our method predicts user interests much more accurately than the previous time-decay-based method.

著者

佐藤 正平 狩野 均

出版者

一般社団法人 人工知能学会

雑誌

人工知能学会論文誌 (ISSN:13460714)

巻号頁・発行日

vol.25, no.2, pp.311-319, 2010 (Released:2010-02-25)

参考文献数

25

被引用文献数

2

---

In this paper, we propose a new method to obtain the transition rules of two-dimensional cellular automata (CA) that performs grayscale image processing. CA has the advantages of producing complex systems from the local interaction of simple elements, and has attracted increased research interest. The difficulty of designing CA's transition rules to perform a particular task has severely limited their applications. So, the evolutionary design of CA rules has been studied. In this method, an evolutionary algorithm was used to evolve CA. In recent years, this method has been applied to image processing. Rosin has studied the evolutionary design of two-dimensional CA to perform noise reduction, thinning and convex hulls. Batouche et al. and Slatnia et al. employed genetic algorithm to investigate the possibility of CA to perform edge detection. In the previous methods, 2-state CA was used for binary image processing. Unlike the previous methods, the present method uses 256-state CA rules to perform grayscale image processing. Gene Expression Programming (GEP) proposed by Ferreira is employed as a learning algorithm in which the chromosomes encode the transition rules as expression trees. Experimental results for the reduction of impulse noise, salt-and-pepper noise and gaussian noise show that the proposed method is equivalent to previous methods in performance and more than 100 times faster than the method proposed by Rosin. We show that the rule obtained by the proposed method employs symmetry-based strategy in the noise reduction process and this property can reduce complexity of CA.