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The model defines key concepts including datums, datum features, datum targets, and the relationships among these elements. A related portion from STEP (ISO 10303-47) Part 47 is reviewed and compared with the new DSCDM, with diagrams and test cases used to evaluate validity. Technical conventions and EXPRESS-G notation are described.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/a-conceptual-data-model-of-datum-paper/663916/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/a-conceptual-data-model-of-datum-paper/663916.png","ImageObject",300,407,{"name":92,"@type":93},"Ben ","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-30","2026-10-29",true,{"@type":102,"interactionType":103,"userInteractionCount":19},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What is the DSCDM described in the paper?","Question",{"text":112,"@type":113},"DSCDM (Datum System Conceptual Data Model) is a conceptual data model that defines the semantics needed for electronic exchange of GD&T data, focusing on datum systems, datums, datum features, and datum targets.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"Which standards are used to derive the DSCDM requirements?",{"text":117,"@type":113},"The paper states that requirements come from existing GD&T drawing-based standards such as ASME Y14.5M, ISO 1101, and ISO 5459, and are linked to the author’s larger GD&T model for STEP AP 210.",{"name":119,"@type":110,"acceptedAnswer":120},"How does the paper compare DSCDM with STEP ISO 10303-47 Part 47?",{"text":121,"@type":113},"A portion of the Part 47 data model is reviewed and compared to the new conceptual data model, referred to as the “Part 47 model,” using diagrams and examples to support evaluation.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},663916,1793234093,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":19,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":139,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":129,"read_time":144},2336478951081,"https://ap-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c","Volume 104, Number 4, July–August 1999  \nJournal of Research of the National Institute of Standards and Technology  \n\n| [J. Res. Natl. Inst. Stand. Technol. 104, 349 (1999)]\u003Cbr>A Conceptual Data Model of Datum |  |  |  | Systems |\n| --- | --- | --- | --- | --- |\n| Volume 104 | Number 4 |  |  | July–August 1999 |\n| Michael R. McCaleb\u003Cbr>National Institute of Standards and Technology,\u003Cbr>Gaithersburg, MD 20899-0001 |  | A new conceptual data model that addresses the geometric dimensioning and tolerancing concepts of datum systems, datums, datum features, datum targets, and the relationships among these concepts, is presented. Additionally, a portion of a related data model, Part 47 of STEP (ISO 10303-47), is reviewed and a comparison is made between it and the new conceptual data model. | Key words: data model; datum; datum feature; datum system; datum target.\u003Cbr>Accepted: June 3, 1999\u003Cbr>Available online: [http://www.nist.gov/jres](http://www.nist.gov/jres) |  |\n\n1. Introduction  \nTraditionally, geometric dimensioning and tolerancing (GD&T) requirements have been exchanged with technical drawings. However, with the advent of computer-aided design, manufacturing, and inspection equipment, the ability to exchange these requirements in a computer-sensible manner has become increasingly more desirable. As “a data model is an effective technique to define the shareable semantics that are essential to the success of data communication in an integrated environment” [1], a conceptual data model has been developed that defines a portion of the semantics necessary for the electronic exchange of GD&T data among the design, manufacturing, and inspection divisions of an enterprise. The portion of the semantics that this data model defines encompasses the concepts of datum systems, datums, datum features, and datum targets. This paper presents this data model, which will be referred to throughout the remainder of the paper as the DSCDM (Datum System Conceptual Data Model) . Additionally, a portion of the data model presented in STEP Part 47 [2] is reviewed and a comparison is made between it and the DSCDM. The model presented in STEP Part 47 will be referred to as “the Part 47 model” throughout the remainder of this paper.  \nNOTE—Though the scope of the DSCDM is limited to the concepts mentioned above, the aim is to provide a foundation upon which more comprehensive GD&T data models may be based.  \nNOTE—The following conventions are employed throughout the course of this paper. To distinguish between EXPRESS entities and the objects they represent, entity names are printed in bold type and the objects they represent are printed in non-bold type. Furthermore, entity names start with a leading uppercase letter (e.g., Datum is an entity name and datum refers to the object) . Attribute names are printed in italic type (e.g., established_datum ) . Additionally, permissible values from enumerated data types are printed in all uppercase letters (e.g., MAXIMUM_MATERIAL_PRINCIPLE) .  \nNOTE—The data models in this paper are presented in EXPRESS-G notation. EXPRESS-G is a graphical notation that supports a subset of the EXPRESS data modelling language. Both EXPRESS and EXPRESS-G  \nare defined in ISO 10303-11 [3] . An overview of the EXPRESS-G notation is presented in Appendix A of this paper as an aid to those who are unfamiliar with EXPRESS-G.  \n2. Requirements  \n“The first step in data modeling is to define the data requirements” [1] . In regard to the DSCDM, the requirements came from existing GD&T drawing-based standards (e.g., ASME Y14.5M [4], ISO 1101 [5], and ISO 5459 [6]) . The reason that these existing GD&T standards are used to define the requirements of the DSCDM is due in part to the fact that the DSCDM is based on parts of a larger GD&T model that the author developed for STEP AP 210, Electronic assembly, interconnect and packaging design [7] . With the increased geometric complexity of printed circuit boards, printed circuit assemblies, ","cbCaiu8WKTDbMXBk","https://ap.wps.com/l/cbCaiu8WKTDbMXBk","pdf",258581,52,"English","# Introduction\n# Requirements\n# Geometric Dimensioning and Tolerancing Definitions","[{\"question\":\"What is the DSCDM described in the paper?\",\"answer\":\"DSCDM (Datum System Conceptual Data Model) is a conceptual data model that defines the semantics needed for electronic exchange of GD\\u0026T data, focusing on datum systems, datums, datum features, and datum targets.\"},{\"question\":\"Which standards are used to derive the DSCDM requirements?\",\"answer\":\"The paper states that requirements come from existing GD\\u0026T drawing-based standards such as ASME Y14.5M, ISO 1101, and ISO 5459, and are linked to the author’s larger GD\\u0026T model for STEP AP 210.\"},{\"question\":\"How does the paper compare DSCDM with STEP ISO 10303-47 Part 47?\",\"answer\":\"A portion of the Part 47 data model is reviewed and compared to the new conceptual data model, referred to as the “Part 47 model,” using diagrams and examples to support evaluation.\"}]","A Conceptual Data Model of Datum - Paper | PDF",131]