Expert Systems with Applications 38 (2011) 10484–10492 Contents lists available at ScienceDirect Expert Systems with Applications journal homepage: www.elsevier.com/locate/eswa Ontological functional modeling of technology for reusability Janghyeok Yoon a, Joohyung Lim a, Sungchul Choi a, Kwangsoo Kim a,⇑, Cheol-Han Kim b a b Department of Industrial and Management Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Namgu, Pohang 790-784, Republic of Korea Department of IT Management Engineering, Deajeon University, Daejeon, Republic of Korea a r t i c l e i n f o Keywords: Functional models Ontological functional modeling Technology reuse a b s t r a c t Technology reuse is important in that it dramatically reduces lead-time, efforts and costs in R&D activities coping with market drivers. In this perspective, understanding technologies from a functional viewpoint helps us search reusable technologies from various technology domains and reuse them. Function is the concept to abstract intention and ways of a technology from a technological standpoint, and reusable function as the core function is representative of the technology. Functional model which formalizes function is represented as an affecting action and one or more affected objects. If technologies and their reusable functional models are stored together in a knowledge base, it is possible to develop a foundation of the environment that allows us to find out reusable technologies by function-based search without regard to technology domains. In this environment, therefore, identifying reusable functionalities from a technology and representing their meanings clearly are the basis to stimulate technology reuse. As a part of constructing the environment for technology reuse, this paper suggests an ontological functional modeling methodology of technology which is composed of a procedure for extracting reusable functionalities and a WordNet-based representation to define ontological functional models. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Functional specification defines what the functionalities will be, but not yet how these functionalities will be implemented. According to Altshuller (1984) and Mann (2002), keywords- and categories- based search provides us with the possible new solutions restricted within specific technology domains, but function-based search offers a useful starting point to first identifying and then finding out more about what alternatives there may be. That is, function-based search is a very effective way of finding out and reusing technologies stripping away the boundaries that exist between different industries and scientific disciplines (Mann, 2002). Currently there are many definitions of function (Kitamura, Kashiwase, Fuse, & Mizoguchi, 2004). However, function in this paper is the concept to abstract intention and ways of a technology from a technological standpoint, and reusable function as the core function is representative of the technology. Functional model which formalizes function is represented as an affecting action and one or more affected objects. If technologies and their reusable functional models are stored together in a knowledge base, it is possible to develop a foundation of the environment that allows ⇑ Corresponding author. Tel.: +82 54 279 2195, fax: +82 54 279 5998. E-mail addresses: janghyoon@postech.ac.kr (J. Yoon), yanzi@postech.ac.kr (J. Lim), blissray@postech.ac.kr (S. Choi), kskim@postech.ac.kr (K. Kim), chkim@dju.kr (C.-H. Kim). 0957-4174/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.eswa.2011.02.090 us to find out reusable technologies by function-based search without regard to technology domains. As shown in Fig. 1, from a functional viewpoint a technology can be abstracted by one or more reusable functional models. Conversely, if we understand the technological functionalities that are required to develop a technology, we can search the alternative technologies that deliver the functionalities and have already developed. For example, in Fig. 1 it is possible to reuse the technologies that deliver the functional model ‘filter gas’. Engineers can find out the technology TA and TE by the function-based search. After reviewing how these alternative technologies deliver the functional model, they can adopt one of the alternative technologies which provide a solution to the problem they are facing. Finally they reuse the way of the selected technology directly or after proper modifications. This function-based search allows us to find out reusable technologies domain-independently and supports technology reuse effectively. Technology reuse helps reduce leadtime, efforts and costs to cope with market drivers (Petrick & Echols, 2004). Therefore issues about identifying and representing the reusable functionalities of technology are important to construct the environment for technology reuse. Most researches on functional modeling have mainly focused on the functional details description of mechanical systems and the formalized terms for functional models. Researches on functional structure are not adequate for identifying and representing reusable functionalities from a technology because their objectives are to describe hierarchical functional details of mechanical J. Yoon et al. / Expert Systems with Applications 38 (2011) 10484–10492 10485 Fig. 1. Functional viewpoint of technologies and function-based technology search. systems (Kitamura et al., 2004; Stone & Wood, 2000; Stone, Wood, & Crawford, 2000). Many researches about how to represent functional models arrange the terms used in functional modeling (Hirtz, Stone, McAdams, Szykman, & Wood, 2002; Hundal, 1990; Pahl & Beitz, 1984) but it is difficult for their approaches to support the function-based search effectively because they lack in how to represent the semantic meanings of the terms explicitly. To solve these problems, this paper suggests an ontological functional modeling methodology composed of a functional modeling procedure and an ontological functional model representation. First, the functional modeling procedure which uses the FAST Diagram in Value Engineering (Miles, 1972) is a procedure to extract reusable functions from a technology. For example, in Fig. 1 it is needed to address how to derive the reusable functions such as ‘filter gas’ and ‘absorb gas from liquid–gas’ from the technology TA. Employed as a technique to analyze functional relations of a technology in this paper, the FAST Diagram is being used widely, and helps functional modelers structurize a technology and extract reusable functions from it. Second, the functional model representation to explicitly define the meaning of functional models adopts an ontological approach. Consider the functional model ‘clear particle’ in Fig. 1. Because in the functional model the action ‘clear’ itself cannot explain whether its meaning is ‘rid of obstructions’ or ‘make bright, light, or translucent’, it is needed to represent its semantic meaning explicitly. An ontology is an explicit specification of a conceptualization (Gruber, 1995). The ontology includes definitions of concepts and an indication of how concepts are inter-related which collectively impose a structure on the domain and constrain the possible interpretations of terms (Uschold, 1998). The ontology is used to improve communication between either humans or computers (Uschold & Jasper, 1999). Therefore ontological functional models can explicitly represent intention and ways of a technology. Additionally they make the function-based search effective and accurate owing to their machine processability. This paper is organized as follows. In Section 2, related works are discussed. Section 3 suggests an ontological functional modeling methodology that consists of a functional modeling procedure and an ontological functional model representation. An example of functional modeling of technology corresponding to the proposed methodology is illustrated through Section 3. In Section 4, a prototype software for the function-based search is introduced. Finally Section 5 concludes the paper. 2. Related works Researches on functional models have been conducted in many areas such as Value Engineering, Engineering Design, and Functional Representations. Their interests are in causal-root relation analysis between functions (Miles, 1972), standardized term definition for functional model representation (Hirtz et al., 2002; Hundal, 1990; Pahl & Beitz, 1984), hierarchical functional structure of mechanical systems (Kitamura et al., 2004; Stone & Wood, 2000; Stone et al., 2000), ontology-based engineering knowledge sharing (Kitamura & Mizoguchi, 2003; Kitamura & Mizoguchi, 2004; Kitamura et al., 2004), application in the computer aided design (Zahng, Tor, & Brinton, 2002), etc. Among these researches, Stone et al. (2000) suggests a heuristic method to figure out mechanical components with modularity by diagramming the function chain of mechanical systems. But their work is not adequate for identifying and representing the reusable functionalities from a technology which are available in other technology domains because it focuses only on describing functional structure and identifying modular components of mechanical products. Hirtz, Stone, McAdams, Szykman, and Wood (2002) categorize possible terms into three-level class types to add formality to functionality representation. The set of terms for functionality representation is called a functional basis (Hirtz et al., 2002). The functional basis by them is believed to be the most advanced since it incorporates the previous efforts by Altshuller (1984), Hundal (1990) and Pahl and Beitz (1984). But their work has limitations in that the terms constituting the functional basis is limited within mechanical systems (Chulvi & Rosario, 2009) and they do not sufficiently provide the explicit meanings of terms. Despite these limitations, the term classification scheme by them is remarkable. Therefore this paper adopts the term classification scheme in order to suggest how to define a domain-specific functional basis in Section 3.2. Kitamura et al. (2004) and Kitamura and Mizoguchi (2003) suggest an ontology-based hierarchical functional structure representation of mechanical systems to share engineering knowledge effectively between engineers. The researches define a functional concept ontology and a device ontology using OWL, an XML-based ontology definition language. The concepts defined in these ontologies constitute functional models. Although their researches seem similar to this paper in the aspect of using ontology, their works are not adequate for how to extract reusable functionalities from a general technology 10486 J. Yoon et al. / Expert Systems with Applications 38 (2011) 10484–10492 because they focus on describing and searching hierarchical functional structure of mechanical systems. Mann (2002) takes a function-based approach to technology reuse. In his book ‘Hands-On Systematic Innovation’, he arranges physical, chemical and biological effects by function, each of which acts as an inspiration to solve the technological problems that engineers face. Through the website of the CREAX function database that is based on his idea, engineers can search various scientific effects to solve specific problems using functions generated from 46 actions and 4 objects (solid, liquid, gas, field) (CREAX, 2009). A distinctive feature of the CREAX function database is that an effect does not always belong to only one function. Namely one or more functions can be derived from an effect according to the functional viewpoint (Mann, 2002). For example, the effect ‘absorption effect’ belongs to the function ‘deposit solid’, ‘extract liquid’ and ‘move liquid’. The functional modeling procedure introduced in Section 3.1 of this paper adopts this feature. But the number of the objects suggested by Mann is only 4, and the actions are outdated because they are originated from the patents until 1984. Therefore it is insufficient to describe intention and ways of the evolving present-day technologies (Chulvi & Rosario, 2009). Additionally Mann does not consider how to extract reusable functionalities from a technology and represent their semantic meanings. That is because his interest is on the basic effects which people can intuitively derive reusable functionalities from. This paper has a differentiation from the Mann’s work in that it deals with how to extract reusable functionalities from various technologies not restricted to the basic effects and how to represent the functionalities formally and semantically. In addition to the above works, researches about engineering reuse by Antelme, Moultrie, and Probert (2000) and Dahmus, Gonzalez-Zugasti, and Otto (2001) are inadequate for identifying and representing reusable functionalities because they focus on product platform, design, standardized parts and product family. 3. Ontological functional modeling of technology As shown in Fig. 2, the final objective of this paper is to suggest how to define reusable ontological functional models from a technology. To do this, first a functional modeling procedure as a preprocessing procedure for ontological functional model representation is suggested to derive reusable functions from a technology. Next a method to represent them into ontological functional models follows. Therefore Section 3.1 suggests a functional modeling procedure using the FAST Diagram in Value Engineering. Section 3.2 addresses how to define ontological functional models using the approach of WordNet (Miller, 1995). The patent US-5031156 ‘method and apparatus for detecting and counting articles’ which has been registered in the United States Patents and Trademark Office is introduced as an example through this chapter. As shown in Fig. 3, the patent is an invention to count the number of articles moving on a conveyer belt in the magazine, newspaper or publishing companies. Using an elastic stick, the previous method counted the number of articles grazing by it. This method had to replace the worn stick periodically with a new one because the worn stick could cause a problem in article counting. Therefore, issues about cost by stick replacement and accuracy by stick wear had arisen. The new method makes the articles vibrate by blowing compressed air, and then sound by the vibration is used to count the number of articles. Owing to the new method, stick replacement became unnecessary and accuracy of counting articles was highly improved. 3.1. A functional modeling procedure for identifying reusable functions Fig. 4 shows a procedure suggested in this paper to derive reusable functions from a technology. The 4-steps, ‘gather key sentences from a technology’, ‘list functions’, ‘make a FAST Diagram’ and ‘select reusable functions’, constitute the procedure. During the procedure, 3 or more domain experts participate to adopt the feature that various reusable functions can be derived from a technology according to the functional viewpoint (Mann, 2002). The suggested procedure uses the FAST Diagram as a tool for identifying reusable functions. The FAST (Function Analysis System Technique) Diagram suggested by Miles (Miles, 1972) is a diagram to structurize interrelations between cause and effect functions rather than to simply describe hierarchical functional details composed of whole and part functions, and is called the Function Diagram. Relating functions according to the ‘How-Why’ logic, it helps people figure out the functions that a system requires and understand relations between functions more effectively. Differently from identifying modular components from mechanical systems by diagramming the function chain (Stone et al., 2000), the objective of the functional modeling procedure in this paper is to identify the reusable functions which are available in other technology domains. The FAST Diagram is adopted because it is widely accepted in many areas and relatively easy to use. In addition, with key sentences of a technology and their functional relations, the FAST Diagram helps understand the core of a technology (Yoon, Choi, Kim, Kim, & Seo, 2010). Fig. 4 shows the steps in the functional modeling procedure together with an example of the above stated patent. Step1 (Gather key sentences from a technology): Step1 is to gather key sentences from a technology. Because functions representative of a technology, or reusable functions, are what abstracts a technology, the gathered sentences have to be about the core intention, inventive principles, ways rather than technological details. For example, details of a circuit design are not in the scope of key sentence gathering. The key sentences in Fig. 4 are ‘articles, moving along a delivery path, are counted by directing a stream of pressured air. . .’, ‘sensors arranged Fig. 2. 2-Steps to define ontological functional models. J. Yoon et al. / Expert Systems with Applications 38 (2011) 10484–10492 10487 Fig. 3. The Patent US-5031156. Fig. 4. A functional modeling procedure. about the air stream detect the acoustic signal which varies with. . .’, the detected acoustic signal is divided. . .’, ‘averaged to reduce the effect of noise. . .’, ‘to generate count signal. . .’, etc. At this step, that 3 or more domain experts individually perform from Step1 to Step4 is required. That is because reusable functions are finally identified by the discussion and expert voting based on individual functional modeling results. Step2 (List functions): Step2 is to list the functions generated from the gathered key sentences. Terms and format for the function representation are not restricted. But they need to meet the form of a natural language which has at least one action and one or more objects. The exemplary functions in Fig. 4 are ‘count the number of articles’, ‘vibrate articles to make sound’, ‘directing a stream of pressured air’, ‘the detected acoustic signal is divided into frequency ranges’, ‘average to reduce the effect of noise’, ‘generate count signal’, etc. Step3 (Make a FAST Diagram): Step3 is to make a FAST Diagram to analyze causal relations between the listed functions. There is the description about modeling notation and diagramming procedure for the FAST Diagram (Miles, 1972). In the FAST Diagram, logical relations between intention and ways represented as functions are structurized effectively. Functions about ‘How’ are on the right side and functions about ‘Why’ are on the left side. Therefore, it is easy to understand the technology at a glance. In the FAST Diagram, functions not main in the technology do not have to be analyzed further. For example, the function ‘rotate roller’ and ‘put article on a conveyer’ in Fig. 4 belong to the listed functions in Step2 but subordinate functions of them are not a matter of concern. Step4 (Select reusable functions): Step4 is to select reusable functions from the functional relation analysis in Step3. In the example of Fig. 4, the reusable functions that domain experts finalized through discussion and expert voting are ‘recognize counting signal’ and ‘vibrate articles’. To check reusability of each function, followings are considered. 1) The function is reusable in other technology domains. 2) The function is the core in the technology. 3) The function is independent and modular. 4) The function represents the engineering intention and ways from a technological standpoint. 3.2. Ontological functional model representation A functional basis is a set of verbs and nouns used to formalize functionalities (Hirtz et al., 2002). The functional basis by Hirtz et al. (2002) is currently believed to be the most advanced and 10488 J. Yoon et al. / Expert Systems with Applications 38 (2011) 10484–10492 Fig. 5. Functional basis by Hirtz et al. (2002). has the structure of primary, secondary and tertiary classes as shown in Fig. 5. The left table of Fig. 5 is a set of verbs, which are called actions in this paper, and the right table is a set of nouns, which are called objects. Terms that have the similar meaning to each class name belong to correspondents. However, a limitation that its terms are limited to mechanical systems was pointed out (Chulvi & Rosario, 2009). In addition, there is not the semantic representation of terms in the functional basis. Consequently with the functional basis, it is difficult to represent and understand the explicit and accurate meaning of the functional models identified in Section 3.1. In order to solve the above problems, this paper suggests how to define a functional basis and make the meaning of functional models clear by adopting the approach of WordNet. The WordNet suggested by Cognitive Science Laboratory of Princeton University (2009) is an ontology database that defines English terms. The WordNet defines the meaning of terms by establishing various semantic relations between terms (Miller, 1995). As shown in (A) of Fig. 6, it defines English nouns, verbs, adjectives, and adverbs and links them through the semantic relations that determine word definitions. (B) of Fig. 6 shows the semantic relations in WordNet, such as a similar relation, an opposite relation, a subor- Fig. 6. An example of WordNet search and the semantic relations in the WordNet (Miller, 1995). J. Yoon et al. / Expert Systems with Applications 38 (2011) 10484–10492 10489 Fig. 7. Functional basis definition and ontological functional model representation. dinate relation, and so on. For example, the 4th sense of the term ‘absorb’ has a similar relation to the 13th sense of ‘take in’ and the 11th sense of ‘take up’, and has an opposite relation with the 2nd sense of ‘emit’. Through these semantic relations, the WordNet forms a semantic network of terms. Therefore, the WordNet is adequate for defining terms of functional models because it focuses on defining and understanding the semantic meanings of words. Fig. 7 shows how to define a functional basis and how to represent the semantic meanings of functional models. First, the starting point for a functional basis is to define a functional ontology. The functional ontology is composed of the WordNet and the domain ontology. Because most of the terms used for functional models representation are general English terms, the WordNet is adequate as an ontology for general English terms. The domain ontology is defined for the domain-specific terms according to the above stated approach of WordNet by domain experts. Developing a functional basis is completed by choosing the required terms from the functional ontology and arranging them with the term classification scheme by Hirtz et al. (2002). To develop a functional basis like this is needed to guarantee the consistency of functional model representation. Next, functional models that are in the form of ‘verb-noun’ or ‘verb-noun1-preposition-noun2’ are represented with the terms in the developed functional basis. Then, the functional models naturally imply the semantic meanings because their terms are in the functional basis where each term refers to a sense of a word in the functional ontology based on the approach of WordNet. Consider the reusable functions identified by the functional modeling procedure in Section 3.1. As shown in Fig. 8, the function ‘recognize counting signal’ and ‘vibrate articles’ can be converted into the formalized function ‘recognize oscillatory signal’ and ‘vibrate plate’ respectively. To formalize the functions is based on a domain-specifically defined functional basis. Then, each term of the formalized functions, or functional models, refers to the functional ontology. Ontological representations of the functional models are ‘recognize(WordNet2.1-recognize-verb-3) oscillatory signal(Mustard1.0-oscillatory signal-noun-1)’ and ‘vibrate(WordNet2.1-vibrate-verb-1) plate(WordNet2.1-plate-noun-1)’. The reference ‘WordNet2.1-recognize-verb-3’ of the term ‘recognize’ is the 3rd sense of the verb ‘recognize’ in the WordNet. The reference ‘Mustard1.0-oscillatory signal-noun-1’ of the term ‘oscillatory signal’ is the 1st sense of the noun ‘oscillatory signal’ in the domain ontology ‘Mustard’. Likewise, the reference ‘WordNet2.1-vibrateverb-1’ of the term ‘vibrate’ is the 1st sense of the verb ‘vibrate’ Fig. 8. An example of ontological functional model representation. 10490 J. Yoon et al. / Expert Systems with Applications 38 (2011) 10484–10492 Fig. 9. Snapshots of a prototype system. J. Yoon et al. / Expert Systems with Applications 38 (2011) 10484–10492 in the WordNet. The reference ‘WordNet2.1-plate-noun-1’ of the term ‘plate’ is the 1st sense of the noun ‘plate’ in the WordNet. In the aspect of using ontology, the functional model representation of this paper seems to be similar to the approach of Kitamura et al. (2004) and Kitamura and Mizoguchi (2003). But this paper has a differentiation in that the functional model representation is not restricted within mechanical systems and based on the approach of WordNet. The WordNet which this paper uses is currently a widely-used and well-defined ontology database that defines the semantic meaning of English terms. Therefore it is possible to cut down the cost and time to develop an ontology for general English terms. In addition, semantic relations defined by the approach of WordNet effectively can support various function-based searches for technology reuse such as similar, opposite, subordinate functional model search, etc. 4. Implementation of a prototype system If ontological functional models derived by the ontological functional modeling methodology in Section 3 are stored together with their technology documents in a knowledge base, then the function-based technology search is possible. This chapter introduces a .NET-based prototype system to define ontological functional models, store technologies and their functional models in a functional knowledge base, and support the function-based search. (A) of Fig. 9 is a functional basis based on a WordNet-based functional ontology and the term classification scheme by Hirtz et al. (2002). Users utilize the functional basis to formalize the reusable functions derived by the functional modeling procedure in Section 3.1. In (A) of Fig. 9, the ontological functional model ‘ABSORB GAS FROM GAS-GAS’ is defined. Because each term in the functional basis has the semantic reference to the functional ontology, the defined functional model has a clear and accurate meaning. (B) of Fig. 9 shows details of the functional model referring to a sense of a term in the functional ontology. In the example, the ontological functional model is ‘ABSORB(WORDNET2.1-ABSORB-VERB-4) GAS(WORDNET2.1-GAS-NOUN-1) FROM GASGAS(MUSTARD1.0-GAS GAS-NOUN-1)’. (C) of Fig. 9 shows a graphical user interface to make relations between technologies and ontological functional models. These relations imply that a functional model can be delivered by various technologies and a technology can be abstracted by one or more functional models. If these technologies and their ontological functional models are stored together in a knowledge base, the function-based technology search is possible as shown in (D) of Fig. 9. Because the functional ontology based on the approach of WordNet defines semantic relations such as a similar relation, an opposite relation, a subordinate relation, a part relation and a manner relation, terms of functional models as the search condition can be used to search the reusable technologies that deliver the same functional models, similar functional models, etc. The software, as a prototype system, supports to search technologies with the semantically same functional models to the functional model in the search condition. For example, in the WordNet, ‘ABSORB(WORDNET2.1-ABSORBVERB-4)’ has the same meaning to ‘TAKE UP(WORDNET2.1-TAKE UP-VERB-11)’ or ‘TAKE IN(WORDNET2.1-TAKE IN-VERB-13)’. And ‘GAS-GAS(MUSTARD1.0-GAS GAS-NOUN-1)’ also has the same meaning to ‘GAS-GAS(DMONTOL1.0-MIXED GAS-NOUN-1)’ or ‘GAS-GAS(POSTAS1.0-MIXED GAS-NOUN-1)’. Therefore, if the search condition for function-based search is ‘ABSORB(WORDNET2.1-ABSORB-VERB-4) GAS(WORDNET2.1-GAS-NOUN-1) FROM GAS-GAS(MUSTARD1.0-GAS GAS-NOUN-1)’, then technologies that deliver ‘TAKE UP(WORDNET2.1-TAKE UP-VERB-11) GAS(WORDNET2.1-GAS-NOUN-1) FROM GAS-GAS(POSTAS1.0-MIXED GAS-NOUN-1)’ or ‘TAKE IN(WORDNET2.1-TAKE IN-VERB-13) 10491 GAS(WORDNET2.1-GAS-NOUN-1) FROM MIXED-GAS(DMONTO1.0-MIXED GAS-NOUN-1)’ also appear on the search results list. 5. Concluding remarks and future study Functional approach can help search the reusable technologies like the objective of the CREAX function database is to search the reusable scientific effects that act as an inspiration (CREAX, 2009). That is, if it is possible to extract and represent reusable functional models from technologies and store them together with technology documents in a knowledge base, the environment for reusing the existing technologies without respect to technology domains will be able to be constructed. Therefore, to identify reusable functionalities from a technology and to represent their meanings clearly and accurately are the key factors to a foundation of the environment for technology reuse. Therefore, the ontological functional modeling methodology which is composed of a functional modeling procedure and an ontological functional model representation suggested in this paper is expected to contribute to the facilitation of technology reuse. The functional modeling procedure dealt with how to identify reusable functions from a technology using the FAST Diagram and the ontological functional model representation explained how to formalize the identified functions and define their semantic meanings using the approach of WordNet. However, this paper still has several limitations. First, this paper suggested how to define a functional basis but not how to guarantee its quality. Despite that the quality of a functional basis which defines terms for functional models affects the quality of ontological functional models, in this paper choosing and finalizing terms for a domain-specific functional basis completely rely on the decision of domain experts. Therefore a study on how to systematically arrange the qualified terms for a functional basis is needed in the future study. Second, this paper did not fully suggest the ontological function-based search mechanism. This paper mainly focused on the ontological functional modeling of technology, and consequently its prototype system simply dealt with a search of the semantically same functional models. Additionally in the future study, using semantic reasoning, the application for function-based search will have to support searches of similar, opposite, subordinate functional models, and how to rank the searched results. Third, the suggested ontological functional modeling methodology requires active participation and cooperation of people. For example, the functional modeling procedure cannot be conducted without participation of domain experts understanding the related technologies, and the experts need to be familiar with the functional modeling procedure. Therefore a software system and a user guideline to facilitate ontological functional modeling of technology are needed to be developed in the future study. 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