Meeting minutes
Minutes review
<kaz> Mar-3
McCool: working on use cases
Martin: also working on use cases
McCool: any objection to publish?
… no objection, approved
Review Proposed Use Cases
McCool's Use Case
<kaz> PR 14 - Define Onboarding Use Case example
McCool: PR #14 Defining onboarding use case
McCool: this PR review can be used to agree on a template
McCool: (review the use case md document in the examples directory)
<kaz> rendered MD
McCool: the format includes a user story: as a (stakeholder) I need (a feature) so that I can (do something of value) , in other words who-what-why
… also includes a section for design alternatives and a section for applications
McCool: (refactoring the document headings)
… how does it look now?
Martin: looks OK
<kaz> updated MD
McCool: (explain the use case)
McCool: how can we import TDs and use them?
… the primary use case is to describe devices and services
… TDs are linked data; it's important to re-export TDs (northbound API)
… We will use TDs to onboard devices
… there are 3 options here
… one is direct graph extension, what is the root of the extended graph?
… another option is to translate TDs into a more suitable format for the graph
… yet another option is through RDF annotation of the TD for connecting the TD to the graph as properties of nodes - similar to option one
McCool: ... an example use case is getting real time data from a temperature sensor in a lake
… are there any changes or additions we should make?
Martin: the template is fine, the detailed assumptions need further review and discussion
… we need to look at options 1 and 3 for potential mismatch
McCool: there are some details we need to prepare detailed examples
Martin: the question is how NGSI-LD and TD relate, where NGSI-LD is a description of the thing (the lake) and the temperature (a property) and the TD could be used as a method for obtaining the value of the property
… we can't just add arbitrary RDF to the graph, so TDs are not a good fit like option one
… Option 3 needs some working out
… maybe there is a conceptual problem with the use case
Martin: what is a thing and what is a Thing Description?
McCool: physical things and software services can be Things in WoT
Martin: how do we then map that into the NGSI-LD world
McCool: there can be non-device entities in NGSI-LD
Martin: maybe entities don't represent network devices
McCool: at the high level example, I want to locate a temperature value onto a map
… NGSI-LD and WoT do different things, and we want to bring them together, the question is how do they connect
Kaz: the discussion is a good direction, for further discussion we should determine what kind of devices and entities we are looking at, some specific entities and devices
Martin's Use Case
<kaz> Issue 15 - Use Case: Thing Description for Thing using NGSI-LD API
Martin: this use case is about the northbound API
… what would a TD look like to describe how to access the thing?
McCool: if you already have an affordance to an entity, the TD would describe how to use the affordance
Martin: need to construct an example TD, how do I map the NGSI-LD operations in the TD?
… how to use the HTTP binding with JSON-LD content
… We map Properties to NGSI-LD Attributes
… there is an issue in that the API currently returns an entire set of Attributes
… We always send full JSON-LD documents in responses
… There may be a Patch interface possible
McCool: another option (2 above) would define a whole new API to mitigate the conceptual differences
… a layer to translate concepts
McCool: we should do a detailed design
Martin: not clear how links and relationships are used
… we don't have actions per se, use updates of Attributes
… looking into Service Execution, which is more easily mapped to TD Actions
… looking at how to make Service Execution more like TD Actions
… for Events, we have Subscriptions which may map to TD Events
McCool: Events and Actions are not described in detail in TD
… but we do have Profiles that can be used to refine the mechanisms
Kaz: suggest that we clarify what specifically, Entities, Things, Services, Applications, etc., is being mapped from NGSI-LD to TD
McCool: we are running out of time, so everyone add comments to the issue
… also add more use cases now that we have more of a template
McCool: The use cases should correspond to northbound and southbound API patterns
AOB
McCool: AOB?
… reminding that we are meeting every week except for some cancellations
… the time offset jumps back at the end of the month
McCool: Any other business?
… Adjourned