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[sdw] HTTP Redirect - with added semantics? (#1270)

From: Jeremy Tandy via GitHub <sysbot+gh@w3.org>
Date: Thu, 24 Jun 2021 12:34:45 +0000
To: public-sdwig@w3.org
Message-ID: <issues.opened-929183414-1624538082-sysbot+gh@w3.org>
6a6d74 has just created a new issue for https://github.com/w3c/sdw:

== HTTP Redirect - with added semantics? ==
### Problem summary:

The HTTP 303 redirect that's commonly used to relate real-world features to their digital counterpart(s) is a hack. There are no semantics conveyed - nothing to explain what information is conveyed by the resource you're being redirected to. But, it's the best of a bad bunch of options.

We often have many digital counterparts for a given real-world feature - each conveying different information, different semantics. 

We typically use Content Negotiation (conneg) when resolving the URL for an information resource. That's fine if you want to choose GeoJSON instead of GML (e.g. choose the media type), but that doesn't help with semantics. There are typically many digital counterparts to a real-world object, each conveying different types of information.

Rob Atkinson (& co.) have long been working on the use "profiles" to characterise and describe the semantics of a domain-specific content model (?) that's encoded in a widely used data format.

But we can't use conneg to select by profile. 

Finally, we still have issues around use of the canonical URI for the real-world feature. We often see people using the URL of the digital counterpart in their applications when they're intending to talk about the real-world thing itself.

So this often means that we're not sure that we're talking about the same thing or not. We need to make sure that applications are using the stable, canonical identifier to talk about a given resource.

An unsolved challenge is determining who's talking about (i.e. publishing information about) a given resource. We sometimes refer to this as "in-bound links". Search engines are beginning to use structured markup in information resources to pull together all information relating to a specific resource into a single search result. But there's no transparent infrastructure in place to support this kind of aggregation.

These challenges are commonly seen in the Augmented Reality (AR) world.

Given all of the above, information discovery and use tends to work in practice. Albeit with some offline/out-of-band schema sharing to provide the semantics for the information.

### Proposals to remedy these challenges include:

- A specific HTTP redirect code with semantics about the connection between physical and cyber domains (this would need liaison with IETF). The (S)ELFIE project proposed a new 306 Redirect "See Feature Description" HTTP code with specific semantics.
- The OGC Disaster Pilot 2021 recommended use of a "switchboard" resource that keeps track of all authoritative descriptions of the resource, so that data users can find the information representation that's relevant to them. This may be an emerging practice in the Best Practice doc?
- Content Negotiation by profile. Progressing conneg by profile would be an IETF task, see the recent discussion in the IETF HTTP API WG, e.g., [https://mailarchive.ietf.org/arch/msg/httpapi/1OUzbFITjwXufIzJe6SKSXjdLfI/](https://mailarchive.ietf.org/arch/msg/httpapi/1OUzbFITjwXufIzJe6SKSXjdLfI/)
- Agreeing a best practice for a query parameter to select an information resource according to its profile type, e.g. "?_profile={my-profile}". 
- Engage with initiatives like schema.org to make it easier to aggregate information from multiple digital resources that are talking about a given real-world feature.

### Next steps:

- Write a SDW-WG paper / note to systematically describe the problem outlined above, essentially to articulate the cases where search / discovery is not working. By way of example, the Web of Things community did this in their Web of Things Discovery note: [https://w3c.github.io/wot-discovery/](https://w3c.github.io/wot-discovery/). 

### Background information:

This topic has been discussed at two SDW-IG plenary calls:

- March 2021 ([https://www.w3.org/2021/03/22-sdw-minutes.html](https://www.w3.org/2021/03/22-sdw-minutes.html))
- May 2021 ([https://www.w3.org/2021/05/27-sdw-minutes.html](https://www.w3.org/2021/05/27-sdw-minutes.html))



Please view or discuss this issue at https://github.com/w3c/sdw/issues/1270 using your GitHub account


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