# Ontology Development - Tensile Test Ontology (TTO)

## Abstract
This document is supposed to provide information on the development of an ontology in the field of materials sciences and engineering (MSE) realized within the project Platform MaterialDigital ([PMD](https://materialdigital.de)). Besides its informative character, this document will allow the developers to explain, register and secure distinct decisions made during the ontology development process. As such, it serves as a log book.

The material's characterization process of the tensile test on metallic materials at room temperature (henceforth simply referred to as 'tensile test') was selected for ontology development. Moreover, the tensile test is to be ontologically described in accordance with the standard DIN EN ISO 6892-1:2019-11. In particular, terms, definitions and symbols given in the standard will be used in the ontology which will be denoted as 'tensile test ontology (TTO)'. The resulting TTO is supposed to be publicly available on the [PMD website](https://materialdigital.de) (download section, available after free registration) and the [PMD GitHub](https://github.com/materialdigital) repository.

## Documents | Links
In this section, some documents are listed (and linked, if applicable) that are supposed to support the ontology creation. Some of the documents might be considered as a part of the ontology creation process (such as, e.g., the development of a Thesaurus).

*Some of the linked documents are freely available, others are stored in internal repositories.*

+ [Repository of TTO development](https://int-gitlab.int.kit.edu/architektur/pmd-tensile-test/-/tree/master/pmdao/tensile-test) | files will be stored here, e.g., visual ontology development applying diagrams.net / Ontopanel plugin tools
+ [Standard ISO 6892-1:2019-11](https://www.beuth.de/de/norm/iso-6892-1/316885984)
+ [Tensile Test Thesaurus](https://int-gitlab.int.kit.edu/architektur/pmd-tensile-test/-/blob/master/pmdao/tensile-test/process-parameter-tensile-test.md) | *already created by PMD*
+ [earlier version of tensile test ontology](https://int-gitlab.int.kit.edu/architektur/pmd-tensile-test/-/blob/master/pmdao/tensile-test/pmd_tt_new.ttl) | *internal repository*
+ [Concept Board](https://app.conceptboard.com/board/gruu-5euo-efm8-5ekf-s2pa?invitationid=6145b390-1735-497e-8517-bf3dd6730bb9) | *collection of ideas and modelling approaches*
+ [Tensile Test Data structure](https://int-gitlab.int.kit.edu/architektur/pmd-tensile-test/-/tree/master/pmdao/tensile-test) | *developed in association with DIN ad-hoc working group*
+ [Ontology Development Guide](https://git.material-digital.de/ontologies/pmd-ontologies/-/tree/main/Presentations) | *developed in the frame of the PMD project*
+ [Curation process Guide](https://int-gitlab.int.kit.edu/architektur/pmd-tensile-test/-/tree/master/curation-process) | *additional information on how to curate an ontology*
+ Other / higher-level ontologies (EMMO, BFO, PROV-O, …)

## Development process | log
### Ontology Development Steps
1. Usage of all necessary and supporting information (see documents | links above)
2. Creation of concepts and plausible relations (T-Box) between them on a visual basis using diagrams.net / Ontopanel plugin (or any visual diagram creator)
3. Conversion into OWL / TTL (e.g. using built-in conversion plugin of Ontopanel)
4. Annotation and curation of concepts using Protégé tool (e.g. including definitions of concepts, classes, object properties, entities using annotation / comment functionality)
5. Verification (e.g. by simple reasoning in Protégé)

Since the development of ontologies is an iterative process that might include both, the possibility and the demand to adjust and extend the ontology, the development steps presented above are also iterative and may be used in repeated sequence. In particular, steps 2 and 3 may be repeated numerously after findings in step 5 and also possible changes concerning implemented content.

### Design Principles | Decision log
In this section, **design principles** used to model the TTO and, especially, underlying modelling decisions are logged and explained with a focus on modelling goals.

#### Fundamentals ####
+ many class definitions allowing interconnection / interoperability / reuse
+ object properties condensed to a lower number to reach clarity
+ reusage of known and well-established concepts / schema, such as in the field of datatype definitions
+ including labels using *rdfs:label* (*rdfs:preflabel*; *rdfs:altlabel*) and definitions as *rdfs:comment* (using Protégé tool) for human readability
+ MSE (domain) knowledge is included in class definitions - on the one hand by including human readable definitions given in natural-language as well as by implementing class relations on the other
+ human readable identifiers for better understanding - labels as well as class / object property designation lead to enhanced queryability
+ PMDco (core ontology = mid-level ontology) is used as basis for ontology development, i.e. basic classes and properties, which are themselves related to higher-level ontologies, are frequently used

| Aim / modelling goal| Decision / modelling approach | Remarks / Explanation |
| -------- | -------- | -------- |
| Integration of generic terms and definitions from the field of MSE | Usage of higher-level ontology EMMO | Since basic concepts of the MSE world are to be included, concepts already given in EMMO are used to avoid doubled work.|
Include concepts of (characteristic) parameters to the characterization method description. Q: Where to put such parameters conceptually - to TT process or test piece? | Due to the general modelling approach using the mid-level ontology PMDco which is developed in parallel, such parameters are connected as 'output' to the process. | In general, this modelling is process-centered as the ontology is supposed to focus the tensile test process and respective data originating therefrom. Therefore, especially, characteristic values are semantically connected to the process. Data distinctly referring to the test piece are accordingly connected to the test piece. |