# Meeting Notes - 31.08.2023

**Participants**:
- [x] Casper Welzel Andersen
- [x] Rickard Armiento
- [x] Francesca Lønstad Bleken
- [ ] Matthias Büschelberger
- [ ] Stuart Chalk
- [ ] Kathrin Frei
- [x] Jesper Friis
- [ ] Emanuele Ghedini
- [ ] Luca Ghiringhelli
- [ ] Gerhard Goldbeck
- [ ] Saulius Grazulis
- [ ] James Hester
- [ ] Antanas Vaitkus
- [ ] Nathan Daelman
- [x] Ilaria Maria Paponetti

## Catch-up after summer

A lot of work has been done considering how crystallographical "models" and concepts fit into the initial ontology work we have been doing.
In this regard a push towards more "models"-based development has happened. I.e., starting from the concept of a "unit cell" or a "single crystal model" and adding other crystallographical concepts and ideas around it.
Especially concepts that bind together CIF properties/attributes/fields to define the implicit ideas and "models" has been explored. This is general important concepts to have in the final ontology and the core of why we're doing this work. But the approach forward; how to implement this with EMMO as the base, is unclear.

## Where to go

We are discussing how to go forward to represent the relation between concepts that are not directly represented in CIF. For example, a 'structure' is composed by a 'cell', 'sites', etc. These concepts exist in CIF, but their relationships are not represented (it is implied by the data for them existing in the same CIF file). But, in the ontology we want to be able to represent this.

Two different approaches forward:

### Equation-based description via PhysicsEquation or equivalent

In our discussion we keep coming back to "models". EMMO does use "models" in the parts around Item -> CausalObject -> CausalSystem -> PhysicalBasedModel -> PhysicsEquation. We can center our ontological modelling on the Laue equations (which should be a "PhysicsEquation" or at least a "PhysicsBasedModel" in EMMO) and then use the common physics-type thinking in "models" to derive all other ontological concepts out of their relationship to the Laue equation (and other such equations).

### Icon-based description via unit cell which is part of the physicalistic perspective approach

We could adopt the unit cell as a physicalistic part of the actual crystal sample. We can then use the semiotic perspective (possibly via icon) to describe semiotic signs (icons) that represent the full sample, etc. (In that sense this is the same thing as a "model" in the physics sense, but this type of description of a sample puts more focus on the semiotic signs as representing the physical object.)