3.1 Framework
The construction of domain ontology needs to determine the domain and scope of the ontology at first. The domain oriented in this paper is the field of equipment defects, which is to integrate and manage the data related to data defects of various structures and provide basic data services for the specific application of upper-level equipment maintenance. The Fig. 1 shows the construction framework of equipment defect field.
As shown in Fig. 1, the overall construction framework of equipment defect domain ontology is shown. The construction framework is based on the seven step method proposed by Stanford University and combined with the idea of ontology evaluation in methodology method. After determining the domain and scope of the ontology, the next step is to construct an ontology for the field of equipment defects, which is used for the unified management of equipment defect related data with multiple structures. The main work is to define the classes. This work includes defining concept cores and constructing the concept hierarchy based on the core classes. After this work, we should define the relationship between concepts in a formal way. The reuse of existing related ontologies can be considered to define the concepts and the relationship between them, which can significantly improve the efficiency of ontology construction. After defining the relationship between the domain related concepts, we should define the properties. This part of work needs to combine the characteristics of existing data sources. The sets of properties are defined according to the existing structure of various types of data. After completing the construction of ontology, the constructed ontology needs to be evaluated. The main content of this paper is to investigate whether the constructed equipment defect domain ontology can effectively organize the current equipment defect data. If not, continue to adjust the sets of concepts and modify the relationship between them until the ontology is evaluated.
3.2 Construction of core concept set
This section is mainly to define the set of concepts involved in the equipment defect domain ontology. First, list the important terms in the equipment defect domain and collect domain concepts that may be used. Second, construct the set of equipment defect domain concepts after sorting and analyzing. If it is time-consuming and laborious to build concepts from scratch, we can consider reusing the concepts involved in the equipment defect management process. Table 1 lists the collection of concepts extracted from the existing equipment defect business process.
The defect business process can be divided into four parts: defect discovering, defect reporting, defect handling and defect eliminating. Defect discovering includes defective equipment information (such as device type, parts, manufacturer, etc.), power network topology information (such as voltage level, power line, etc.), discoverer information (unit, team, etc.), and defect specific description information (defect description, content, cause, etc.).
defect reporting includes the registrant information (work group, registration time, etc.), the confirmation information of defects (such as classification basis, defect nature, etc.) and System generated defect information (such as defect ID, corresponding defect standard library, etc.).
Defect handling includes OMS information of the defects (such as OMS ID, OMS defect ID), information of the person in charge of the work (such as ID of the person in charge of the work, receiving unit, etc.) and information of the inspection and construction proposals (such as the inspection and repair proposals, repair categories, etc.).
Defect eliminating mainly includes defect elimination information (such as elimination date, etc.), acceptance information (such as acceptance team, acceptance unit, acceptor, etc.), and defect handling result information (such as legacy problems, reasons for delay, whether missing or not).
Table 1
Sets of core concept base on equipment defect business process.
Equipment defect business process
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Sets of core concepts
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Defect discovering
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defective equipment information
power network topology information
discoverer information
defect specific description information
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Defect reporting
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registrant information
confirmation information of defects
System generated defect information
|
Defect handling
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OMS information of the defects
information of the person in charge of the work
inspection and construction proposals
|
Defect eliminating
|
defect elimination information
acceptance information
defect handling results information
|
Based on the relevant core concepts proposed in Table 1, we combined the characteristics of existing data sources and introduced some new concepts to build a set of core classes. Taking the equipment defect as the core, referring to the basic ontology design concepts such as "people, events, things and rules", combined with the equipment defect business and model, the equipment defect ontology is constructed by selecting the team, equipment, equipment defect, defect description, defect treatment, defect elimination and acceptance, family defect and defect management documents as the main vertex concepts. At the same time, we divide the core concepts in the field of equipment defects from four dimensions. They are equipment information, defect information, organization, and defect management documents.
Equipment information: equipment information includes equipment, manufacturer, and topology information of the defective equipment.
Defect information: it covers the classification and treatment of equipment defects and other defect businesses, and defines equipment defect treatment, defect elimination, family defects and other contents.
Organization: it covers the management and implementation of equipment defects, and defines the organization and personnel involved in defect management.
Defect documents: management rule documents covering equipment defects. This part defines documents, specifications, guidelines, and other contents.
Table 2
core concepts divided by dimensions
Dimension
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Concept set
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Organization
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Team, acceptor, registrant, discoverer, defect eliminator
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Equipment information
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Power grid, manufacturers, parts, suppliers
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Defect information
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Defect description, defect treatment, defect elimination acceptance, family defects
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Defect document
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Standard specification, documents, guideline system
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As shown in Table 2, the core concept set of equipment defect field is divided based on four dimensions. The concept set of these four dimensions is summarized to form C in the quad.
3.3 Construction of relations between concept sets
In the previous section, the core concept set in the field of equipment defects is constructed based on four dimensions. The main content of this section is to determine the relationship between the concepts in the core concept set. In the constructed concept set, equipment defect is a very important concept, and other concepts will be directly or indirectly related to the concept of vulnerability. Therefore, this section starts from the equipment defect to construct the relationship.
Family defect is the sub concept of equipment defect, and family defect and equipment defect are the sub concept relationship. The equipment defect occurs on a certain part of the equipment, so the relationship from the equipment defect to the equipment and parts is expressed by occur. Defect description is a specific description of specific defects, so the relationship from equipment defects to defect description is represented by describe. For equipment defects, the defect management document plays a guiding role in defect handling operation and defect elimination and acceptance operation. Therefore, the relationship between the defect management document and equipment defects is expressed by guide, and the relationship between defect handling and defect elimination and acceptance is operate. The treatment of equipment defects is carried out by specific teams, so the relationship between equipment defects and teams is represented by handling.
Then make a specific analysis for the specific concept set of each dimension. In the organizational dimension, the acceptor, registrant, discoverer and defect eliminator belong to their corresponding teams, so their relationship is represented by subclass of.
In the dimension of equipment information, each equipment has its own power grid topology, so its relationship is represented by belong to. The manufacturer produces the equipment, and the supplier supplies the equipment. Therefore, manufacture represents the relationship between the manufacturer and the equipment, and supply represents the relationship between the supplier and the equipment. Each part of the equipment constitutes the components of the equipment, and each part of the equipment constitutes the specific equipment. Therefore, the relationship between parts and components and between components and equipment is represented by composition.
In the dimension of defect documents, standard specification, guideline system and documents are three important components of defect management documents. Subclass of is used to express the relationship between them and the concept of defect documents. Under the standard norms, there are defect classification standards and defect terminology standards. In terms of the guideline system, technical supervision is an important part of the guideline system, and the relationship between them is expressed by subclass of. The relationship between technical supervision and supervision basis is represented by guide. In the same reason, the relation between technical supervision and supervision requirements is also guide.
In the dimension of defect information, defect description includes two key elements: defect location and defect cause. Therefore, the relationship between defect location, defect cause and defect description are represented by subclass of. The classification basis is an important sub concept in defect description, and the subclass of is used to represent the relationship between defect description and classification basis. The concept of defect elimination acceptance includes the evaluation of the state, specific maintenance operation and specific test operation. We use operation as the relationship between defect elimination acceptance and equipment. Evaluate is used as the relationship between condition evaluation and defect elimination acceptance. The analysis report after each equipment defect contains three parts: rectification measures, experimental data, and analysis summary. We use subclass of to express the relationship between the analysis report and these three parts. The specific relationship between related concepts is shown in Fig. 2.
3.4 Construction of property set
The core concept set of equipment defect domain has been constructed in the previous two sections. If only the core concept set and the relationship between concepts are defined, it is impossible to describe the equipment defect domain in detail. Therefore, in addition to the work done in the first two sections, we also need to describe the internal structure of the concept in detail. In this paper, the internal structure is described by properties. Therefore, the main content of this section is to construct the property set corresponding to each concept in combination with the structural characteristics of existing equipment defect data sources. The following mainly introduces the construction of defect management documents and property sets of equipment defects
3.4.1 Construction of defect information property set
The construction of defect information set mainly refers to the equipment defect Standard Specification, quality event report and specific equipment defect data. The specific equipment defect property set is integrated. Through the integration of each property set, the redundant properties are removed, and the similar property are uniformly named.
3.4.2 Construction of property set of defect management document
The construction of defect management document property set mainly refers to the standard specification, guideline system and detailed supervision rules. The specific management document property set is integrated, the redundant properties are removed, and the similar properties are uniformly named.
3.5 Evaluation of domain ontology
Ontology evaluation is an essential link in the process of continuous iteration and improvement of ontology. The following is a qualitative analysis and evaluation of the constructed equipment defect domain ontology from four aspects: conceptual integrity, conceptual correctness, conceptual scalability, and relationship scalability between concepts.
Conceptual integrity: the concept set involved in the ontology should contain important concepts in the field of equipment defects. The core concepts of ontologies constructed in this chapter are extracted from the existing formed ontologies in the field of equipment defects. These ontologies cover all levels and aspects of the field of equipment defects, with wide coverage and meet the requirements of integrity.
Conceptual Correctness: the concepts in ontology should be clear and accurate without ambiguity. We analyze the core concepts one by one, and there is no ambiguity in each concept.
Concept Extensibility: the concept extensibility of ontology is mainly reflected in the continuous addition of new concepts according to the actual situation in the application process of ontology, so that the ontology can be continuously improved. We divide the core concept set of equipment defect domain ontology into four dimensions. With the enrichment of data sources, we can add subclasses from four dimensions and establish new relationships, to continuously expand the ontology, Make the ontology more perfect.
Integrity between concepts: it mainly measures the integrity of the relationship category between concepts. The equipment defect domain ontology constructed by us includes various relationship categories such as cause and effect, use, dependency and so on. The relationship categories are rich, and the equipment defect processing process can be modeled through these rich relationships.