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AW: Thing Description for existing data sources

From: Kovatsch, Matthias <matthias.kovatsch@siemens.com>
Date: Mon, 13 Jun 2016 14:20:32 +0000
To: Michael Koster <michael.koster@smartthings.com>
CC: "Charpenay, Victor" <victor.charpenay@siemens.com>, "public-web-of-things@w3.org" <public-web-of-things@w3.org>, "Public Web of Things IG" <public-wot-ig@w3.org>
Message-ID: <4EBB3DDD0FBF694CA2A87838DF129B3C017D5842@DEFTHW99EL4MSX.ww902.siemens.net>
There is no problem with Web linking techniques. I wanted to express the following clash I see:

On the one hand, I see a type system that defines a data structures from primitive types (a technique that I would associate with RPC-style distributed systems). It lacks the possibility to describe individual elements semantically. If two applications have the same elements, but in a different structure, I would expect that a WoT machine can automatically convert structure A into its own structure B - or in other terms, can understand the meaning of each individual element in structure A and map it to its internal data model.

On the other hand, I see semantic annotations that define meaning of an interaction or resource. A machine can learn what elements are important for the interaction at an information model level, but not how to serialize it. With the current type system, we can only describe how anonymous elements are structured. The explicit definition of which information-model element must go where in the structure needs to be defined in parallel to the strucuture.

Those two definitions need to be unified.

Personally, I see representation format definitions doing that (e.g., SenML defines structure and semantics in one place). However, the definitions are not machine-understandable, not even machine-readable. Thus my comment, that we should think about this "something completely new" that enables us to define representation formats in a machine-understandable way (i.e., structure and semantics of elements in one place). This would also enable the pluggable approach the Web has been relying on to be evolved: a fixed well-designed core and plugins that help with the application problems of a specific time (cf. pre-Web 2.0 vs post-Web 2.0). The type system is currently overburdening the TD. We need to divide-and-conquer...


Von: Michael Koster [mailto:michael.koster@smartthings.com]
Gesendet: Montag, 13. Juni 2016 15:45
An: Kovatsch, Matthias (CT RDA NEC EMB-DE)
Cc: Charpenay, Victor (CT RDA NEC WOS-DE); public-web-of-things@w3.org; Public Web of Things IG
Betreff: Re: Thing Description for existing data sources

On Jun 10, 2016, at 10:34 AM, Kovatsch, Matthias <matthias.kovatsch@siemens.com<mailto:matthias.kovatsch@siemens.com>> wrote:

The schema only defines the structure. Somehow we need to attach the semantic annotations directly in the schema. I think schema.org<http://schema.org/> goes in this direction, but has the other issues you identified.

[ Matthias] I think we need something completely new. It would help to properly collect the requirements, identify the closest matches and elaborate from there.

What is wrong with using web linking techniques (hyperlinks) with link relations and link attributes to carry the application semantics? Thing Description already has the ability to include more RDF property types to indicate these relations/attributes and they can be resolved to full descriptive URIs using json-ld.

Rather than try to attach application semantics to schemas, I suggest we go the other way around, and attach schemas to semantic descriptions.

I'm not sure why the payload format and application semantics must use the same description mechanisms at all. There may be good reasons to use one method (link relations and attributes) to carry application semantics and another method (templates, json-schema) for describing payload structure and data type (number, string, boolean, time, etc.)

As I recall, the issue with schema.org<http://schema.org> was in it's lack of ability to describe the data types we think we need. There is nothing stopping schema.org<http://schema.org> from being easily extended with property types that describe payloads. Schema.org<http://Schema.org> is only the semantic ontology; it can describe anything we want, and can be used to describe payloads by linking to json-schema instances ot other template formats.

I am working with schema.org<http://schema.org> and some other organizations on use cases and strawman designs for bringing schema.org<http://schema.org> to IoT/WoT including any new requirements like payload schemas and type descriptions. There will be some examples from this activity to review and evaluate soon.

I agree that we need to have the requirements and use case clearly defined before we evaluate solutions.

Best regards,

Received on Monday, 13 June 2016 14:21:17 UTC

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