- From: Manfred Hauswirth <manfred.hauswirth@deri.org>
- Date: Tue, 22 Dec 2009 19:34:47 +0000
- To: Michael Compton <Michael.Compton@csiro.au>
- CC: Semantic Sensor Network Incubator Group WG <public-xg-ssn@w3.org>
I agree with Michael.
What about "A sensor implements a process"? The process may be
implemented in hardware (=> device) or in software or a mix. Sensors can
be components of more complex sensor.
Cheers,
Manfred
Michael Compton wrote:
>
> Maybe I should just address the dot points.
>
>
>> - A process has inputs and outputs
>
> ok
>
>> - A system has components
>
> ok
>
> (1)
>> - A sensor is a process
> (2)
>> - *Some* devices are sensors
>> - Some devices are sensors - because they have an output
>
> are we saying that a sensor is a process or that sensing is a process.
> For example, lets say:
>
> * I have a device that measures wind chill (i.e. it measures temperature
> and wind speed and does a calculation), by (2) above it's a device that
> is-a sensor, and by (1) it must be a process (I'm uncomfortable with
> this already because we have now said that a device is-a process, which
> seems wrong to me. I'd think a device might follow some process, but
> this is-a relationship seems strange).
>
> * Now what if I write down the wind speed and temperature measurements
> myself and do the calculation myself. What's the sensor here? It can't
> really be me, can it - it would seem strange to say that I am a process
> and a sensor. Seems more like I followed a process and thus calculated
> wind chill. So maybe the sensor is the process I followed? Or is it the
> act of me following the process? In either case we have a problem
> because above we said a device is-a sensor and then here we are saying
> something entirely different (a process or the act of following it) is-a
> sensor.
>
> I would say that a device cannot be a sensor (well not in the process
> sense that we have been talking about) otherwise we are conflating an
> abstract (a process) and a concrete thing (a device).
>
> Seems from all the discussions that we have had that sensing is-a
> process - or that some processes result in sensing something, and that a
> device or a person, or a regional observing system might act out such a
> process and thus sense something.
>
> So I would be more comfortable with
>
> - Sensing is a process
> - Some devices can act as sensors
>
> And then that a device that senses something could be a 'sensing
> device', which thus acts out some sensing process.
>
> but I don't agree with (2) above
>
>
>> - *Some* devices are systems
>
> Why aren't all devices systems? Even if they only have one component or
> we don't want to write down all their components?
>
>
>> *- Some systems are sensors*
>
> It depends, is our definition "A system has components" or "All things
> with components are systems"? The question itself is silly, but my
> point is why are we trying to use the same component relationship to
> describe devices and processes?
>
> I'm having trouble seeing the example above with me calculating wind
> chill as a system.
>
>
> Michael
>
>
>
>
>
>
>
>
>
> On 20/12/2009, at 2:19 , Luis Bermudez wrote:
>
>> Hi Michael,
>>
>> The only thing we have said about systems is that it contains
>> components...
>>
>>
>>
>> On Fri, Dec 18, 2009 at 12:42 AM, Michael Compton
>> <Michael.Compton@csiro.au <mailto:Michael.Compton@csiro.au>> wrote:
>>
>> my conceptions/preconceptions/misconceptions are as follows.
>>
>> - A sensor need not be a physical device. Kevin's definition of
>> "An entity capable of observing a phenomenon and returning an
>> observed value." seems ok to me.
>>
>>
>> agree !
>>
>>
>>
>> - A Sensor need not be a single entity - it can be composed of any
>> number of sub sensors, each perhaps of their own identity, each
>> perhaps measuring different things that get combined into the whole.
>>
>>
>> This is why it can be a system . Maybe we need to add also:
>>
>> *Some sensors are systems*
>> **
>>
>>
>>
>> - The following things 'are' sensors
>> *a temperature sensor (i.e. a physical device) at location l
>> *a program on a computer (far away from location l) that can read
>> in the temperature at location l and a wind speed estimate for
>> location l and calculate the windchill at l
>>
>>
>>
>> Yes.. Commonality is that a sensor has an output and therefore are
>> processes.
>>
>>
>>
>> More correctly, in both cases something has acted as a sensor for
>> a particular phenomenon: a device in the first instance, and the
>> program in the second - if I wrote down the temperature and wind
>> speed measurements on a piece of paper and calculated the wind
>> chill myself, then I have acted as the sensor.
>>
>> - The example of the wind chill sensor means that sensors can have
>> multiple components, and I guess the components may themselves be
>> interesting.
>>
>> - A device (a physical piece of hardware) can also be broken down
>> into components (presumably other devices, but perhaps also
>> systems - software systems etc) but I don't see that as having
>> anything to do with sensors or their decomposition into parts.
>> For example, imagine a device that can measure wind speed and
>> temperature, that has a small inbuilt chip that can calculate wind
>> chill, round measurements, compute averages and a radio to
>> communicate its readings. It's physical decomposition into its
>> components is different from its decomposition into the roles it
>> can play as a sensor. So the two sorts of decomposition may be
>> related, but not equivalent.
>>
>>
>>
>> So I think this still holds true:
>>
>> - Some devices are sensors - because they have an output
>> - Some devices are systems - because they have components
>>
>> But if you wnat to propose other statements which make the system
>> composition more explict, please do so.
>>
>>
>>
>>
>>
>> - I'm also unsure about the word system and in particular it's
>> relationship to process.
>>
>>
>> We are separating them..
>>
>>
>> - partly I see the problem as linguistic: i.e. we are using the
>> word sensor in two different contexts. We think of things in
>> terms of 'ah this thing is a sensor', but we also say 'a sensor is
>> a process'. Is what we are really saying that to sense something
>> is to follow a process that leads to a value as an estimate of a
>> phenomenon. In which case a sensor isn't a thing at all it's
>> really a 'to sense do...' or 'was sensed by doing...'. So if we
>> take it that to sense something is to follow a process that
>> estimates a value, then what is a system and why is a sensor one?
>> To think of a system as a collection of components in some
>> technical sense and then make sensor one of these is to take the
>> 'ah this thing is a sensor' approach, but then we also agree on 'a
>> sensor is a process' which now seems to make a sensor not a
>> system. So is the biggest problem here simply that we (copying
>> from SWE) have decided that systems have components and sensors
>> are also made up of things, so it must be a system - where as
>> there are actually two hierarchies here and we should represent
>> them with different relationships?
>>
>>
>>
>> The only think we are saying about sensor is that it has an output !
>>
>>
>>
>> So how about....
>>
>> a System is a device/computer system/software system that is made
>> up of components
>>
>>
>> I think we do not need to be explict about device/computer
>> system/software. For example, a regional observing system can also be
>> a system.
>>
>>
>> a Sensor is a process (a description of inputs/outputs, some steps
>> and data flows) which may also be made up of sub sensors
>>
>>
>> yes.
>>
>>
>>
>> a System may play the role of a sensor for phenomenon X.
>>
>>
>> So is this OK ?
>>
>> *- Some systems are sensors*
>>
>>
>> but I suggested before that *Some sensors are systems*
>> **
>> I think both are ok.. what do you think ?
>>
>> -luis
>>
>>
>>
>>
>>
>> Michael
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> On 17/12/2009, at 19:11 , John Graybeal wrote:
>>
>>
>> On Dec 16, 2009, at 12:00, Manfred Hauswirth wrote:
>>
>> Hi John,
>>
>> thanks for your insightful comments. Some more comments
>> from my side.
>>
>> John Graybeal wrote:
>>
>> Regarding "all systems are processes": Honestly, I
>> would not >
>>
>> understand this (I stated this at the F2F). For me,
>> you have
>> systems > which include one ore more processes. If
>> systems are
>> processes, why > have systems at all. My notion of
>> systems would
>> informally consist > of processes, scenarios,
>> deployments, etc.
>> The question "why have systems at all?" is the crux
>> here. Can we
>> state clearly when a process is not a system? Or in
>> other words,
>> how is a system more narrow than a process?
>> Incidentally, my notion of processes would informally
>> consist of
>> the same list. I am also having trouble drawing the
>> distinction.
>>
>>
>> Interesting! I think this may be due to our different
>> background (I
>> assume your are not a computer scientist like myself - without
>> evidence I may add).
>>
>>
>> Computer Science and Statistics. 30 years software and systems
>> support. (No worries!)
>>
>> In my area (computer science, information systems) systems
>> would be
>> defined as I do and a system would consist of software and
>> hardware
>> and the processes would clearly be "inside" the system as
>> part of
>> the software, so there is a clear distinction between
>> "system" and
>> "process" (other CS/IS people - please feel free to
>> contradict me),
>> whereas you seem to define this more from the viewpoint of an
>> experiment which is being observed (?) where processes
>> come into
>> play as part of the observation process (please correct me
>> - I am
>> guessing here).
>>
>>
>> I'm using one of the general meanings of the word 'process', which
>> applies not just to what's happening in side the computer or
>> component, but what happens as all the software and components
>> interact with each other. There are local processes and there are
>> external processes.
>>
>> It isn't driven by experiment orientation but by broader CS
>> orientation -- dealing with engineering systems of systems, and
>> including the human component in those systems, and modeling
>> all the
>> above as processes (which may, or may not, then be
>> computerized in the
>> new version of the system). Anyway, just a different viewpoint,
>> neither right nor wrong.
>>
>> The problem here seems to lie in different
>> conceptualizations in
>> different communities - all of which done according to the
>> specific
>> needs of a community. Now, while this may complicate
>> things, I think
>> it is also a useful and actually mandatory exercise. While
>> I may
>> claim, that I need to understand the conceptualization
>> because as an
>> CS/IS person I will have to build (software/hardware) systems
>> (sorry! no other term comes to mind) which need to manage
>> information coming out of observations, you may claim
>> exactly the
>> same from you point of view (and rightfully so). The
>> question now
>> for me is: Who are our users and how to serve them best?
>> Where's the
>> sweet spot?
>>
>>
>> Concur. I presumed from the start that the group was interested in
>> modeling hardware elements, but I have found it useful to consider
>> those hardware components as processes in a larger system of
>> systems.
>> They take data in and transform it to other data that is spit out.
>> This is one useful definition of a process, as Luis notes.
>>
>> Oops, got off track there! But our agreed point is to agree on
>> which
>> type of devices (= which group of users) we want to make the
>> ontology
>> for. My assumption/preference was the group that used physical
>> devices to transform measurable phenomena into digital data
>> (because
>> that's the easiest to model and the most immediately useful).
>> But I
>> can go with whatever on this, as long as we all understand.
>>
>> PhysicalSystem: I don't remember the exact reason
>> for this. Did
>>
>> we > mean deployment?
>> I assume this is to distinguish it from a software system.
>>
>> Sensor as subclass of Device: I think this is too
>> narrow. I can
>> think of sensors which are not devices at all,
>> e.g., human
>>
>> "sensors" > in the context of social sensing (which
>> is an accepted
>> concept in > many domains including CS by now).
>> Making sensors a
>> subclass of > device limits us to purely technical
>> systems in
>> hardware, IMHO. Is > an RSS feed a device? I can
>> clearly use it as
>> a sensor. I think that > Device should be a subclass
>> of Sensor.
>> Even in existing middelware > systems like our GSN we
>> followed
>> that path (without having an > ontology in mind at all).
>> This gets to purpose of the ontology. As I understood
>> it, the
>> group was originally constructed to model hardware
>> sensors. (May
>> have just been a wrong assumption on my part. More
>> precisely, what
>> we clearly were not doing is modeling samplers, that
>> is, devices
>> that return a physical sample.)
>>
>>
>> Agreed. But "sensors" do not necessarily manifest
>> themselves as
>> hardware. If I want to detect user activity / inactivity on a
>> computer in an experiment, one of my sensors may be a the
>> keyboard,
>> another one running processes (not waiting for user
>> input), etc. It
>> is very hard to draw the line here. My question: Do I have
>> to have
>> this distinction at all? Essentially I convert an X into a
>> Y and Y
>> should be usable in a computer. Whether X a is a physical
>> phenomenon
>> or not depends on the domain, IMHO.
>>
>>
>> Sure, that works for me too. If you make a sensor too general,
>> though, it can have components. What do we call those
>> components --
>> are not at least some of them sensors? So now, what is
>> different from
>> the sensor that can have sensors, and a device, which has the same
>> recursion into smaller devices; and a system, which can have
>> systems
>> (and a process, that can have processes)?
>>
>> I'm being a little silly of course. All I mean to do is call
>> attention to the need to define the terms according to what
>> makes them
>> different from each other, not just whether they are higher or
>> lower
>> in a hierarchy. I think we haven't done that well enough yet.
>>
>> So using one definition of sensor ("anything that
>> senses") makes
>> Sensor very broad, and other things would subclass to
>> it. (Since
>> some devices (a hammer) don't sense things, we'll have
>> to define
>> Device narrowly to make it a subclass Sensor.) Using
>> another
>> definition of sensor ("a component that detects
>> (measures) a
>> physical phenomenon, converting it into a digital
>> representation
>> that can be output to other components"), a Sensor is
>> clearly a
>> specific type of Device, and is also a component of
>> any sensing
>> device.
>>
>>
>> If you see software as a Device, I would agree to it, but
>> then again
>> Device has the connotation of hardware.
>>
>>
>> Ah, I said a Sensor was hardware in my original world, so I didn't
>> have any problem here -- since my Sensor was hardware and my
>> Device
>> had a sensor, I was already on board with Device being hardware.
>>
>> Do we have a set of definitions by any chance, so we
>> can all use
>> these (or some) terms the same way?
>>
>>
>> I don't think we have.
>>
>> Why is a Device a subclass of a Process? A Process
>> can use
>>
>> Sensors > which are manifested as Devices to
>> do/measure something,
>> IMHO. Again > this is a quite narrow notion of the
>> concepts.
>> I'm not following your argument here. Yes, a Process
>> can use
>> Sensors as you say. So can a Device. There is no
>> inconsistency
>> that I can see. This suggests a Device is in fact a
>> type of Process.
>>
>>
>> Sorry, but I don't understand how a Device can be a Process.
>>
>>
>> The "Process: something that receives an input and produces an
>> output"
>> is not a sufficient explanation or model of that?
>>
>> John
>>
>>
>> Best regards,
>>
>> Manfred
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> Luis Bermudez Ph.D.
>> Coastal Research Technical Manager
>> Southeastern Universities Research Association (SURA)
>> bermudez@sura.org <mailto:bermudez@sura.org> - Office: (202) 408-8211
>> 1201 New York Ave. NW Suite 430, Washington DC 20005
>
--
Prof. Manfred Hauswirth
Digital Enterprise Research Institute (DERI)
National University of Ireland, Galway (NUIG)
http://www.manfredhauswirth.org/
Received on Tuesday, 22 December 2009 19:35:29 UTC