[Data-modeling] relationship type explanations... diagrams?

[Danny Hillis]

There may be a few properties, like Density that apply to most  
materials, but most properties can be grouped according to  how the  
material is used. For example, a property like Yield Strength is  
important to structural materials, whereas a properties Refractive  
Index is important to optical material. These should be different  
types that may inherit from a common included general material type. A  
material like quartz, which is used as both, it can be co-typed as both.

It may even be that the same underlying physical property is treated  
differently depending on how that material is used. For instance,  it  
is important to know know the Mohs hardness for a mineral and the  
Vickers hardness for a ceramic, or the dielectric  constant of an  
insulator vs. the index of refraction on an optical material. The fact  
that they are physically the same property is not as important as the  
way they are used.

The best way to do this may be to group properties into categories  
that have similar properties such as fluids, glasses, metals, and  
polymers. Note that we already have Element and Chemical Compound.

I would suggest that the first thing to do would be to design a  
hierarchy of material types and run that by some potential users, like  
me.
-Danny


On Jun 3, 2008, at 3:56 PM, jerritt collord wrote:

> I'm new here and not sure how normalized I need to think--or what  
> I'm missing--or if I'm just having a bad day and need to re-read.
>
> Quick explanation of problem: I'm not an engineer but an area I'm  
> interested in tangentially is materials science. There are tons and  
> tons of possible properties as one might imagine and I don't think  
> the right solution is to create a Material type with ~100 properties  
> slots. Or maybe it is?
>
> Obviously the physical properties have to integrate with the fairly  
> complete system of basic Units in freebase... but e.g. there will be  
> a lot of mechanical properties all with Units that now carry Units  
> of Pressure designation.
>
> I know this isn't fruitful, but this is what I tried to do:
> -------
> type: MaterialPropertyClass
> display is Enumeration
> example instances: Mechanical property, Magnetic property, Chemical  
> property, Health property
>
> type: MaterialProperty
> display is Standard
> properties:
> * base SI Unit (single value: reference to appropriate instances of  
> system Unit type)
> * alternative units (multiple values: reference appropriate  
> instances of system Unit types)
> * MaterialPropertyClass (single value: reference to instance of  
> MaterialPropertyClass, display as disambiguator)
> example instances: Density, Magnetic Susceptibility (many of these  
> topics already exist, unstructured, in freebase probably via  
> wikipedia)
>
> type: MaterialPropertyMeasure
> display is Compound (?)
> properties:
> * Material
> * MaterialProperty (single value: references MaterialProperty)
> * MaterialPropretyValue (single value: floating point number)
> * MaterialPropertyUnits (reference to sytem Unit type)
> * MaterialPropretyDesc (single value: text) -- used for non-numeric  
> Properties, or descriptions of measurements
> example instances: Density of Stainless Steel
>
> type: Material
> properties:
> * etc.
> * MaterialsPropertyMeasure (multiple values) ? Here's where I fail  
> to understand... it seems that what I'd want to do is have all the  
> instances of MaterialPropertyMeasure that reference this material  
> show up.
> ----------
> Probably too complicated and all but encourages users to stray from  
> standard units--and unqueryable to boot.
>
> Any guidance for examples of domains/problems that resolve  
> relationships like these? Basic reading I need to do more of?
>
> Thanks,
>
> Jerritt
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