Re: State of SSN: arguments in favour of a single name and namespace, proposal, the SEAS example, proposal of action

Hi Phil,

So the question is whether they use different namespaces. Personally, I
> believe they should.


I would also like to have your opinion on the pertinence of my other
arguments regarding communication and usability.


> This makes the distinction clear for anyone looking
> at instance data. If instance data only uses SOSA, there's no need to
> look at/consider SSN axioms. If there's just one namespace, you won't
> know from the instance data whether it was created with or without
> knowledge/use of the extra semantics.
>

Now that's another point. Inference capabilities / entailment regime (as
per SPARQL 1.1). I will try to convince you that again, one namespace would
be preferable than two.

Suppose we use two namespaces sosa: and ssn:. You suggested to delete terms
from ssn that already exist in sosa.  This means there would not exist
ssn:Sensor, but there would be a sosa:Sensor.

Suppose there is a document somewhere with the following content (let's
forget about prefix declarations):

```
ex:mysensor a sosa:Sensor
```

As the consumer of the instance data, how do I know if the publisher wanted
to use the SOSA or the SSN-new entailment regime? ssn:Sensor does not exist
anyways.

The only possibility to make it work is to keep duplicates for every term
in the ssn namespace, and add some note that:

"if a RDF Graph contains sosa terms, then you should use the sosa
semantics. If a RDF Graph contains ssn terms, then you should use the ssn
semantics".

--> That brings confusion in the same REC. What happens if some instance
data contain both sosa and ssn terms ? What happens if I want to integrate
instance data containing sosa terms with instance data containing ssn terms
? what happens if I want to extend SSN with additional axioms ? ...


Suppose now we have only one namespace ssn:. My instance data becomes

```
ex:mysensor a ssn:Sensor
```

As the consumer of the instance data, and in the absence of any mention of
a owl:Ontology, then It's completely up to me to use the SOSA or SSN-new
entailment regime. I have no means to know what the publisher had in mind.
That problem is unrelated to SSN, or SDW. In the absence of some
owl:Ontology in the document, I currently cannot know what the entailment
regime shall be.

On the other hand, as the publisher of this instance data, I *can make this
explicit* by adding an OWL ontology that imports SOSA, or SSN-new. I would
serve instead the following documents:

```
ex: a owl:Ontology; owl:imports ssn:Vocabulary .
ex:mysensor a ssn:Sensor
```

or:

```
ex: a owl:Ontology; owl:imports ssn:Ontology .
ex:mysensor a ssn:Sensor
```

Besides, I think this issue always remains. Anyone on the web could define
and publish an ontology that adds semantics to such ssn terms. If he then
serves instance data that use ssn terms and his ontology, the
aforementioned method can make explicit the entailment regime to be used.

Kind regards,
Maxime