Units with prefixes and composed units

[chrwm]

Description of the issue

When annotating data in practice some units might not be present in the OEO. This could be specific units, as cited below, or units that appear more frequently in our domain, such as kW, MW, GW - which are all not present in the OEO yet.

I understand the units are imported from the "Unit Ontology" and find it strange that some units have more detailed prefixes, e.g. mass unit -> picogram, gram, kilogram, ..., than others.

Unit with prefix annotation: If units have a prefix such as kilo, giga etc. it is usually appended to the unit with k-, g- etc. and this way a part of the unit. Sometimes it happens that there is column with a certain measurement magnitude e.g., column “passengers (thousand)”. How should the “thousand” in such a case be handled? As a kilo to the unit like a normal prefix or as a kilo-concept to the parameter reference?

Originally posted by @lumi321 in OpenEnergyPlatform/oeplatform#1107 (comment)

Composed and rather rare units I'd consider to implement on demand in the future.

Ideas of solution

Add units that are frequently used in domain but still missing in OEO, such as

• kilowatt
• megawatt
• gigawatt
• ...

TODO check rest of UO to complete list

Workflow checklist

• I am aware of the workflow for this repository

[stap-m]

Composed and rather rare units I'd consider to implement on demand in the future.

But implementing on demand might be slow. We should at least discuss how to deal with composed units in general, e.g. €/MW.

[l-emele]

This is a very important issue and we probably won't solve it as issue discussion. So I put it on the agenda for the next oeo dev meeting. https://etherpad.wikimedia.org/p/oeo-dev-49

[lumi321]

Related to this is issue OpenEnergyPlatform/oeo-extended#10 about specific units.

[l-emele]

We had yesterday the physical meeting on composed concepts. We made progress, but do not have a final solution. Thus I postpone this issue.

[stap-m]

Related to #1690

[l-emele]

@chrwm : I suggest to close this issue now:

• With issue Composed units need relations #1815 / PR Add object properties for composed units #1816 we implement the necessary object property for relating units to the unit components.
• With the oeo-extended we have place to manually (and in future automatically) add composed units,

If you agree, please close this issue.

[stap-m]

I reopen this issue. We need a relation between units and prefixes. Either we use 'has part' or create a subproperty 'has prefix':
For example: Gigawatt EquivalentTo watt and 'has prefix' some giga
This is important for oeo-extended as well.

[l-emele]

The units ontology has the object property has_prefix. My understanding was that this will be imported, but seemingly we forgot this in #1690

[UStucky]

For an example of quantity-related classes (OO software) see #1510

[stap-m]

The units ontology has the object property has_prefix. My understanding was that this will be imported, but seemingly we forgot this in #1690

The thing is that the IRI of has_prefix http://purl.obolibrary.org/obo/has_prefix leads to an error...

[stap-m]

I'd propose to create a proper oeo relation has prefix and add the "may be identical to" annotation to relate to the above mentioned obo relation. A def could be:
A relation between a unit and a prefix that indicate the magnitude of the unit.