how to associate a process with a immaterial entity (was spatial region)?

[dr-shorthair]

I'm modelling the capture of data associated with a spatial region, e.g. in the context of remote sensing and imagery.
The sensor is pointed at a region with the intention of ultimately characterizing its contents.
But in the initial phase, while the content is not known, the spatial boundary is.
So in my application I've defined region of interest as a subclass of spatial region with the definition:

"Spatial region that is the subject of investigation or observation".

I'd like to axiomatize it properly, so this requires associating it with the process of image capture.

(The process-flow for remote sensing involves one or more Planned Acts:.
Act of Observation, Act of Measuring, Act of Information Processing are already included in the EventOntology. )

I'm looking at the object-properties that have process as the domain.
has participant (and its sub-properties has input has object affects) looks like the right connection point.
But it explicitly excludes spatial region in the range.

1. Why the specific exclusion?
2. How can I allow a process to refer to a spatial region?

@avsculley @paulhed @JJBittner @DanielleZLimbaugh

[JJBittner]

@dr-shorthair The short answer is that has participant is not the right relation for this case, and in Basic Formal Ontology (BFO) it cannot be used for a spatial region.

In BFO, has participant has domain process, but its range explicitly excludes spatial region. Its range is:

specificially dependent continuant or generically dependent continuant or (independent continuant and not spatial region)

So an assertion like:

:imageCaptureAct bfo:has_participant :regionOfInterest

would not merely be a questionable modeling choice. If :regionOfInterest is asserted as a subclass or instance of spatial region, then that use conflicts with the stated range of has participant.

The deeper issue is that a region of interest should not be modeled as the site or spatial region itself.

A site is an independent continuant. It persists as the site that it is whether or not anyone is currently observing it, targeting it, tasking against it, or treating it as operationally relevant. By contrast, being a region of interest is dependent on an information or planning context. A site may become a region of interest because a battle is occurring there, because a sensor is tasked against it, or because a Tactical Operations Center (TOC) has identified it as relevant. After the battle ends, or after the TOC moves on, that same site may no longer be a region of interest.

If RegionOfInterest were modeled as a subclass of site, then this would incorrectly make region of interest status intrinsic to the site as an independent continuant. That is not what is intended. The site persists, but its status as a region of interest does not.

So I would model RegionOfInterest as a Generically Dependent Continuant (GDC), more specifically as an Information Content Entity, that is about a site, spatial region, or independent continuant. This is similar to the way a name such as "Paris" is not the site itself, but an information content entity that designates or is about the site occupied by Paris. The site persists independently. The designation or interest status depends on an information bearing context.

For example:

:RegionOfInterest
subclass of Information Content Entity
and is about some Site or Spatial Region

or, if you want to keep the operational targeting sense clearer:

:RegionOfInterestSpecification
subclass of Information Content Entity
and is about some Site or Spatial Region

Then the planned act can use that information content entity as an input:

:ImageCaptureAct
subclass of Act of Observation
and has input some RegionOfInterestSpecification

The image or observation record produced by the process can also be about the same site or spatial region:

:RemoteSensingImage
subclass of Information Content Entity
and is about some Site or Spatial Region

This separates three things that should not be collapsed:

1. The process, such as an image capture act.
2. The independent continuant or spatial region where the process is located or toward which it is directed.
3. The information content entity that identifies something as a region of interest.

If the intent is to say where the image capture process occurs, then use a location relation:

:imageCaptureAct bfo:located_in :someSiteOrSpatialRegion .

That places the process.

If the intent is to say what the tasking order, observation plan, capture request, image, or observation record is about, then use an information content relation:

:roiSpecification123 cco:is_about :site123 .

:someCaptureAct cco:has_input :roiSpecification123 .

:capturedImage123 cco:is_about :site123 .

A generically dependent continuant, such as an information content entity, is not located in a spatial region in the same way a material entity or process is. Its bearer may be located somewhere, but the information content entity itself is about something. What it is about may be a site, a spatial region, or independent continuants located there.

This also handles the remote sensing case cleanly. In the initial phase, the boundary or site may be known, while the contents are unknown. The region of interest specification can be about the site or spatial region without asserting what material entities are contained there. Later, after observation or information processing, additional assertions may be made about entities detected at or located in that site.

So I would not define RegionOfInterest as:

"Spatial region that is the subject of investigation or observation."

That definition makes region of interest status sound intrinsic to the spatial region.

A better definition would be:

"An information content entity that designates a site, spatial region, or independent continuant as the spatial scope of an act of observation, measurement, information processing, or operational attention."

In short:

Use located in to place the process. Use is about or designates to connect the region of interest information content entity to the site, spatial region, or independent continuant. Do not use has participant for the spatial region, because BFO explicitly excludes spatial regions from the range of has participant. And do not make RegionOfInterest a subclass of site, because a site persists as an independent continuant, while being a region of interest is dependent on an information or operational context.

[pahed]

@dr-shorthair,
To answer your first question, "why the specific exclusion?", I found in the BFO book (https://www.penguinrandomhouse.com/books/657278/building-ontologies-with-basic-formal-ontology-by-robert-arp-barry-smith-and-andrew-d-spear/9780262527811/?ref=PRHB7BD76FBDB&aid=14813&linkid=PRHB7BD76FBDB), page 108, that immaterial entities divide into two major subgroups: Boundaries/Sites and Spatial Regions. Where the distinction is that boundaries and sites are directly related to material entities, and spatial regions exist independently of material entities. The definition of "process" requires the use of a material entity as a participant, therefore, since spatial regions exist independently of material entities, a process cannot be associated with them and hence the "not spatial region" in the range axiom.

I am not sure what the correct approach is for your second question either what Jay has stated in his response or perhaps your area of interest could be a fiat surface boundary in which case the use of process would work.

[JJBittner]

Thanks, Simon. I think that Barry does a good job explaining why the exclusion exists in his book, that is a must read for anyone building with BFO.

The important distinction is that BFO separates immaterial entities into sites and boundaries on one side, and spatial regions on the other. Sites and boundaries are tied to material entities, while spatial regions are not. Since processes require participants, and participation is grounded in continuants that can participate in a process, spatial regions are excluded from the range of has participant.

So I agree that has participant should not be used to connect an image capture process directly to a spatial region.

I am less sure that the right solution is to model the area of interest as a fiat surface boundary, unless the thing being identified really is a boundary of some material entity. A fiat surface boundary may work if the intended target is literally the surface boundary of a material entity, such as the surface of a vehicle, building, terrain feature, or other bounded material entity. But in the remote sensing case, the “area of interest” often seems to be an operational or informational designation, not the boundary itself.

That is why I think the safer pattern is to distinguish:

1. the material entities participating in the process, such as the sensor, platform, operator, or imaging device;
2. the site or spatial region associated with where the process occurs or toward which the sensor is directed;
3. the information content entity that designates something as the area or region of interest.

On that pattern, the area or region of interest is not itself the site or spatial region. It is an information content entity, or perhaps a directive information content entity, that is about or designates a site, spatial region, or material entity.

For example:

:AreaOfInterestSpecification
subclass of Information Content Entity
and is about some Site or Spatial Region

or, in an operational tasking context:

:AreaOfInterestSpecification
subclass of Directive Information Content Entity
and designates some Site or Spatial Region

Then the image capture act can take that specification as input:

:ImageCaptureAct
subclass of Act of Observation
and has input some AreaOfInterestSpecification

The captured image or resulting observation record can also be about the same site, spatial region, or entities located there:

:CapturedImage
subclass of Information Content Entity
and is about some Site or Spatial Region

This also addresses the temporal issue. A site can persist as an independent continuant before, during, and after the battle or observation event. But being an area of interest is context dependent. A Tactical Operations Center may designate a site as an area of interest during a battle, and later that same site may no longer be an area of interest once the operational context changes.

So I would avoid making AreaOfInterest or RegionOfInterest a subclass of site, because that would make the interest status look intrinsic to the site. I would also avoid making it a fiat surface boundary unless the intended referent is specifically a boundary of a material entity.

In short, I think the model should be:

The process has material participants.

The process may be spatially located in relation to a site or spatial region.

The area or region of interest is an information content entity that is about or designates the site, spatial region, or material entities of concern.

That preserves the BFO exclusion on has participant, avoids making the site itself temporarily become a region of interest, and still supports the remote sensing case where the boundary is known before the contents are known.

[dr-shorthair]

Thanks @JJBittner @pahed for your responses.

1. I'm comfortable that I understand the immaterial entity hierarchy. I understand that site and continuant fiat boundary are anchored to other things so are not appropriate for this purpose.
2. I proposed that region of interest is a subclass of spatial region. This followed from the discussion in https://gitlab.ogc.org/ogc/T21-GIMI/-/work_items/51 . The textual definition follows the genus-differentia form "Spatial region that is the subject of investigation or observation" - i.e. that is subject of a process or more specifically of a planned act. The dimensionality is not limited - from my geophysics background I'm very comfortable with imaging lines (flightlines, boreholes, transects ...) and volumes (in the atmosphere, ocean, and underground) as well as surfaces.
3. An individual region of interest may be the "real-world-referent" of an image, where the region but not the content is known at the time of image capture. So the relation from an Image (of a region) (a subclass of Representational Information Content Entity) to the region of interest (a subclass of spatial region) is represents (cco:ont00001938).
4. The question begged by the textual definition is how to axiomatize the connection between the region of interest and the Planned Act of "investigation or observation" (e.g., image capture). You guys have pointed out that has participant (or its sub-properties) cannot be used in this case since the range is a material entity. occurs at and occurs in are along the right lines, except (i) the range is site or material entity (ii) they seem to presume a local or in situ spatial relationship, and don't seem to allow for a remote spatial association*. Maybe this hasn't come up in the BFO or CCO world before. I've looked at the CCO ExtendedRelationOntology but can't see an existing solution. Are we are treading new ground here?

*One of the key innovations of O&M (the predecessor of the SSN Ontology) was to allow for separate locations for the feature-of-interest and the observer. This enabled in situ, ex situ and remote observations to be described using the same formalization. Previously there had been conflicting ideas about the location of the 'Observation' which had caused problems in interpretation, and difficulties in crossing over between application domains.

@JJBittner you suggest pushing region of interest over into the Generically Dependent Continuant (GDC) branch of the BFO hierarchy. I disagree. The region exists in space, it is not a dependent continuant. The camera is pointed at the region so the image is of the region. We don't know what material things are in the region, so we accept that it is merely a kind of ... a continuant part of the spatial projection of a portion of spacetime at a given time (quote from the definition of spatial region). Specifically, it is one that is subject of investigation or observation. We discussed this at length back in January. Perhaps the subclass is not needed and spatial region is enough. But we can differentiate this kind of spatial region, which usually implies a sub-class.

At some point in the discussion @alanruttenberg agreed and used the phrase 'real world referent for an image' to describe it. That settled it for me. We don't know what is there, but we know where it is. The region has a geometric description (an ICE) that provides the geospatial coordinates of interest. But we don't need another indirection. BFO's spatial region recognises that such an immaterial entity is required, so I'm planning to use it. (Unfortunately I can't locate my record of the discussion with Alan.)

@pahed I have ordered a copy of the BFO book for myself so that we can cross-reference this when necessary.

[DanielleZLimbaugh]

@dr-shorthair — I'd push back on spatial region and argue for Site, specifically CCO Geospatial Region (ont00000472), defined as a Site at or near Earth's surface.

I think the reason you ruled out Site — "anchored to other things" — conflates two material relations. A Site is existentially dependent on the material entity that bounds it, not the ones that fill it. For a geospatial region the bounding anchor is the Earth, which you always know is there; the contents you're trying to characterize are the entities located in the site, and those can stay entirely unknown without affecting its status. So "boundary known, contents unknown" — your initial remote-sensing phase — is precisely what a Geospatial Region already supports: specified by coordinates (asWKT / lat-long-alt), independent of what's inside.

And this is the branch that connects to your Planned Act. A Site is an independent continuant that is not a spatial region, so it's admissible wherever the range reads "...and not spatial region": it can be environs by the act (BFO_0000183), it satisfies the site-or-material range of occurs in, and Geospatial Location (ont00000487) is literally defined as a Geospatial Region that environs a process. The image then represents (ont00001938) that Site — the real-world-referent link you wanted, with no GDC indirection and no overloading of has participant.

A limitation: 1D targets — flightlines, boreholes, transects — are already one-dimensional spatial regions in CCO and can't be Sites. So I'd scope the area/volume region of interest as a Geospatial Region (Site) and handle linear targets separately, rather than forcing one class to subclass two disjoint branches.

And @JJBittner's point about the definition still holds whichever genus we pick: "subject of investigation or observation" is extrinsic and time-indexed. For a real subclass the differentia should be intrinsic, with the "of interest" status carried by the relation to the act, not baked into the kind. As such, this should probably be a defined class.

[JJBittner]

@DanielleZLimbaugh , I think this gets us closer, and I agree with the main corrective move you are making.

For Earth surface cases, I agree that Common Core Ontologies (CCO) Geospatial Region is probably a better candidate than raw Basic Formal Ontology (BFO) spatial region. The hierarchy matters here: Site and spatial region are both under immaterial entity, but Site is not a subclass of spatial region. CCO Geospatial Region is under Site. So if the referent is an Earth surface area, then modeling it as a Geospatial Region means we are not modeling it as a BFO spatial region.

I also agree with your point that unknown contents do not defeat the Site analysis. A Site does not depend on knowing which material entities are located in it. So “boundary known, contents unknown” is not a reason by itself to reject Site or Geospatial Region.

Where I would still push back is on making “Area of Interest” or “Region of Interest” a primitive subclass of either Site or spatial region.

The problem is still the phrase “of interest.” That does not seem intrinsic to the Site or the spatial region. It is assigned by a tasking, plan, investigation, observation objective, collection requirement, or other information artifact. The same Site or spatial region can be of interest during one operational context and not of interest later. So I would not bake “of interest” into the genus differentia of the referent itself.

I think the cleaner pattern is to separate three things:

1. the real world referent, which may be a CCO Geospatial Region, Site, or BFO spatial region depending on the case;
2. the Information Content Entity, or Directive Information Content Entity, that specifies or designates that referent as an area or region of interest;
3. the planned act, observation act, or image capture act for which that designation is relevant.

So for Earth surface cases, I would be comfortable with something like:

Area of Interest Specification
subclass of Directive Information Content Entity
designates some CCO Geospatial Region

For non Site cases, such as flightlines, boreholes, transects, atmospheric volumes, ocean volumes, underground volumes, or projected sensor volumes, I think we may still need the BFO spatial region branch:

Region of Interest Specification
subclass of Directive Information Content Entity
designates some BFO spatial region

Then the image or observation record can represent the actual referent, whether that referent is a Site, Geospatial Region, or spatial region.

So I agree with your correction that Geospatial Region should not be collapsed into spatial region. But I would still keep “of interest” out of the primitive class hierarchy. The referent is real, but the interest status is relational, contextual, and time indexed. It belongs with the specification and planned act, not intrinsically with the Site or spatial region.

[dr-shorthair]

Thanks @DanielleZLimbaugh for your clarification on site vs. spatial region. I'm left wondering, however, what 'spatial region' is for ...

But also thanks @JJBittner for noticing that a region-of-interest for imagery is not necessarily anchored to the surface of the earth. Perhaps that answers the question about 'spatial region'.

However, I reject the idea that dimensionality comes into play in finding the context in the class hierarchy. Imaging happens on all dimensions - 0-D (points), 1-D (lines and curves), 2-D (surfaces), 3-D (volumes, or surfaces over time), 4-D (volumes over time). I've done all of these in geology and geophysics. Not necessarily in the visible spectrum, but the data handling is essentially the same. Sometimes the n-D region-of-interest is anchored geospatially, sometimes it is anchored to another thing (e.g. a microscope slide, an organism). But it is most-usefully understood as a spatial thing until the analysis of the investigation or observation is complete and we have a theory about the material stuff that is inside the region. This is all why I thought 'spatial region' was the appropriate superclass. But maybe that's too low in the hierarchy and I should try 'immaterial entity'.

Now I'd like to tackle the specific concern: that 'of interest' is not intrinsic, and that the 'region of interest' is time-bound, etc.

In most imagery cases the region-of-interest is only associated with a single investigation or observation. A different image (any dimensionality) will rarely have exactly the same bounds. And if it does then that is fine: it is a different region-of-interest as it is associated with a different investigation, which coincidentally has the same geometry.

It really is the association with the investigation or observation that matters. This is not intrinsic to a generic spatial region (or more generally, immaterial entity) but the involvement in an investigation or observation is intrinsic to a region-of-interest. Hence the name. It is nevertheless a continuant since the region is still there later, even though it was defined by the act of investigation or observation.

Other spatial things are defined by acts. A mining claim is defined by the act of pegging the corners. A residential subdivision is defined by an act of the land-titles office. Like other spatial things associated with 'rights', the rights have a specified duration but we'll model it as a continuant since we can still find it later even if we can no longer mine gold there later. (I just spent the weekend in Ballarat, a historic gold-mining area about 100km west of where I live ;-)).

The goal here is to have a thing that an image represents. This might be an artefact, or material thing. But for earth observations (and geophysics) it is immaterial at the time of image capture, and it is critical to know its geometry since this allows us to do the georeferencing that is necessary to make the image data useful. That's all. And since the image was captured through a planned act, then this spatial thing is the subject of the planned act. The latter is the relationship that is called 'hasFeatureOfInterest' in SSN. It is one of the most commonly queried properties in SSN graphs.

I can generally understand @JJBittner story about tasking etc and that is all fine. But it is also useful to name a direct relationship from the image to the thing, and from the planned act to the thing. This might be understood to correspond to a property-chain that describes another route from the image to the thing and from the planned act to the thing. Graphs have multiple routes between two nodes and this is OK.

[avsculley]

Thanks @DanielleZLimbaugh for your clarification on site vs. spatial region. I'm left wondering, however, what 'spatial region' is for ...

@dr-shorthair You're not the only one. There's long been talk of removing it, but it seems to stick around mostly for axiomatic reasons.

[dr-shorthair]

Let's remove the discussion of classes, and look just at the relationship.
After all that was the main topic of this issue, which I've just renamed because clearly the seeds of this debate were sown there, perhaps unnecessarily.

For an Image-content*, when it is a sub-class of Representational Information Content Entity (RICE) (cco:ont00001069) then represents (cco:ont00001938) is good to link it to a site or spatial region, or any other entity in fact.

Looking at the link from a Planned Act. If we set aside the (clearly confusing) spatial region, then has participant looks OK. Maybe the sub-property has object cco:ont00001778 , though its axiomatization doesn't really guide us here.

Does this work? (using words instead of the actual URIs)

<Image-content> rdfs:subClassOf <RICE> .

<myImage345> a <Image-content> ; 
      <cco:represents> <myRegionOfInterest456> .

<myRegionOfInterest456> a <bfo:site> ;
      geosparql:hasBoundingBox <Envelope567> .

<myObservation678> a <cco:ActOfObservation> ;
     <cco:has-object> <myRegionOfInterest456> ;
     <cco:has-output> <myImage345> . 

<Envelope567> a sf:Envelope ;
     sf:minimum <bbmin> ;
     sf:maximum <bbmax> .
<bbmin> a sf:Point ;
     geosparql:hasSerialization "POINT(138.494192 -34.804844)"^^geosparql:WKTLiteral .
<bbmax> a sf:Point ;
     geosparql:hasSerialization "POINT(138.498668 -34.800998)"^^geosparql:WKTLiteral .

*Image cco:ont00002004 is a subclass of Media Content Entity cco:ont00002001. This is too limiting IMAO, or poorly named. I've raised #875 to clarify that. Note one example for RICE cco:ont00001069 is "the content of a photograph of the Statue of Liberty represents the Statue of Liberty". This tells us that image content is understood as RICE, while the Image class focuses on its instantiation in a specific media format.

[DanielleZLimbaugh]

The only thing I'd change is the object of represents. A bfo:Site is an immaterial entity (its boundaries merely coincide with material stuff), so the image content can't depict the site itself. What it depicts is the material entity located in the site. So I'd add that material entity, locate it in the site, and point represents at it:

Image-content rdfs:subClassOf RICE .

myImage345 a Image-content ;
    cco:represents mySiteMaterial456 .          # was: myRegionOfInterest456

# the material located in (bounded by) the Site - what the image actually shows
mySiteMaterial456 a bfo:MaterialEntity ;
    bfo:locatedIn myRegionOfInterest456 .

myRegionOfInterest456 a bfo:Site ;
    geosparql:hasBoundingBox Envelope567 .

myObservation678 a cco:ActOfObservation ;
    cco:has-object myRegionOfInterest456 ;
    cco:has-output myImage345 .

Envelope567 a sf:Envelope ;
    sf:minimum bbmin ;
    sf:maximum bbmax .
bbmin a sf:Point ;
    geosparql:hasSerialization "POINT(138.494192 -34.804844)"^^geosparql:WKTLiteral .
bbmax a sf:Point ;
    geosparql:hasSerialization "POINT(138.498668 -34.800998)"^^geosparql:WKTLiteral .

I want to try an add some clarity to "What is spatial region for?" I apologize for commenting on a class after your attempt to move on.

The difference between site and spatial region is movability and material dependence. A site is an immaterial continuant whose existence depends on the material entities that bound it, so it travels with them — the cockpit of a plane is a site, and it moves with the plane. A spatial region is a part of space itself: material-independent and immovable. It can't move, any more than a temporal or spatiotemporal region can; for those it isn't even coherent to ask.

That immovability is what makes spatial regions load-bearing. Location and motion are defined against them — a continuant is located in / occupies a spatial region at a time, and change of place just is being located in different spatial regions at different times. You need a frame that doesn't itself move to define what moving means, and a site can't supply that: if the frame travels with its material bounds, you can't anchor an absolute position or characterize motion.

So the division of labour is: sites give you functional, matter-tied containers that persist and move with their bearers; spatial regions give you the fixed backdrop that makes location, distance, and motion expressible at all. Even where little instance data is ever typed directly as spatial region, the relations that ground location need it as their range.

[JJBittner]

@DanielleZLimbaugh , I agree with your site versus spatial region explanation, especially the movability and material dependence point. I also agree that if the intended relation is visual depiction, then the image depicts material entities, surfaces, or qualities located in the site, not the immaterial site itself.

But I would be careful saying the image content cannot represent the site. represents may be broader than visual depiction. A georeferenced image can represent or be about the site as its geospatial referent, while also depicting whatever material entities or qualities are located there.

The bigger issue is still cco:has-object myRegionOfInterest456. Since has object is under has participant, and since the proposed object is a bfo:Site, I do not think that relation is safe. The site is not part of the projected state achieved by the observation. It is the selected referent or target of the observation.

I think the safer pattern is that the observation has input some region or area specification, that specification designates the site, and the image is about or represents the site. If material contents are later identified, then the image can also represent those material entities located in the site.

[johnbeve]

Moving this to discussion. Once agreement on a solution has been developed, please open up an issue. @mark-jensen @APCox @neilotte

[dr-shorthair]

@DanielleZLimbaugh wrote

A site is an immaterial continuant whose existence depends on the material entities that bound it, so it travels with them — the cockpit of a plane is a site, and it moves with the plane.

I noticed the definition and examples of site which appear to rely on obvious boundaries within a host - the cockpit of a plane, a hole in a piece of Swiss cheese, a nasal cavity, etc. However, the boundaries of a region of interest of an image are not usually anchored to obvious features in the landscape, but rather to arbitrary geospatial positions. That is why I had leaned towards spatial region rather than site, since it is a purely 'geometric' thing. Of course the location may be tied to the earth or another celestial body. Which leads to the next question: you wrote ...

A spatial region is a part of space itself: material-independent and immovable. It can't move, any more than a temporal or spatiotemporal region can; for those it isn't even coherent to ask.

How do you describe the extent and location of a spatial region?

If the description uses coordinates or angles, then there must be a reference frame. If the frame is tied to a material entity, then the spatial region will move with it.

Is there another way to describe the shape and location of a spatial region, that doesn't use a reference frame?

@JJBittner wrote

I think the safer pattern is that the observation has input some region or area specification, that specification designates the site, and the image is about or represents the site. If material contents are later identified, then the image can also represent those material entities located in the site.

Could you show this in a modified version of the example?

(I find that actual worked examples help both pedagogically and analytically.)

[DanielleZLimbaugh]

@dr-shorthair, I did some research.

Can a spatial region be described without a reference frame? No. Location is a relation: every coordinate needs a frame, and every practical frame is anchored to a material entity. WGS84 is anchored to Earth, a stage frame to your microscope slide, even the ICRF to distant radio sources. Strictly, shape and extent need a frame too. Frames in relative motion disagree about lengths and, because they also disagree about simultaneity, about which three-dimensional slice of spacetime the region even is; only the four-dimensional interval is invariant. Note that BFO's elucidation, "spatial projection of a portion of spacetime at a given time," presupposes a frame twice: once for the projection, once for the time. For sensing the disagreement is negligible (micrometres over 10 km at orbital speeds), but nothing about a spatial region is frame-free in principle.

BFO says as much itself. From the BFO 2.0 Reference, on spatial region: "a spatial region is the sort of entity that can be specified by means of a coordinate frame, and is always at rest relative to this coordinate frame." And on your exact case: "The reference frame might be relative to a moving object such as the earth, in which case the corresponding spatial regions move with the movement of the earth. However, they are at rest relative to their coordinate frame." So "immovable" means immovable within the frame, not absolute. The regions of a frame are the standard against which motion in that frame is measured: a thing moves iff it occupies different regions at different times. Seen from a heliocentric frame, an Earth-fixed region does move. That is two frames disagreeing, not a contradiction. Note that the BFO 2020 axiomatization never formalizes frames; users are told to choose one. The frame is presupposed, not represented.

This also answers "what is spatial region for?" It is the backdrop a frame supplies: the range that occupies spatial region requires, even if little instance data is ever typed there directly. I take that to be @avsculley's "axiomatic reasons."

It also removes your objection to Site. The BFO 2020 elucidation of site has two disjuncts: a three-dimensional immaterial entity whose boundaries either "(partially or wholly) coincide with the boundaries of one or more material entities or have locations determined in relation to some material entity." A site needs no walls; the second disjunct covers fiat boundaries. A WGS84 bounding box is a three-dimensional immaterial entity whose fiat boundaries are located relative to Earth: a site by the second disjunct, and exactly what CCO Geospatial Region is. The same reading covers regions anchored to a slide or an organism. Your mining claim fits the pattern too.

Your 0-, 1-, and 2-D targets have a home in the same branch. Sites are three-dimensional by elucidation, but BFO supplies anchored counterparts at every lower dimension: continuant fiat boundary, with fiat point, fiat line, and fiat surface, carries the same anchoring clause as site ("location is determined in relation to some material entity"). BFO's own examples settle the worry that a fiat boundary must bound some bona fide thing: the fiat line examples include "all lines of latitude and longitude," which are specified by coordinates and bound nothing material. A flightline or transect is a fiat line by the same standard, so @pahed's suggestion was closer than the thread allowed. The anchored side of immaterial entity thus covers every dimension: fiat point, fiat line, fiat surface, site. What BFO lacks is only a name for that union (immaterial entity that is not a spatial region); CCO could define one and use it as the range for regions of interest.

Even so, I would mint the direct relation. Every member of that union is admissible in has participant, so the range axiom is no longer a problem. However, a remote act does not occur at its target, and the target does nothing in the act; it is selected, not involved. That is @JJBittner's "not safe" instinct about has-object, and I think he is right. So: an analogue of SSN's hasFeatureOfInterest, an object property with domain planned act and range continuant, kept out of the has participant hierarchy. The direct relation and Jay's pattern are not rivals. One axiom joins them. Declare a property chain: if an act has an ROI specification as input, and that specification designates a region, then the act has that region as its feature of interest.

# Pattern
ex:hasROISpecification rdfs:subPropertyOf cco:has_input .
ex:isFeatureOfInterestOf owl:inverseOf ex:hasFeatureOfInterest .
ex:hasFeatureOfInterest owl:propertyChainAxiom ( ex:hasROISpecification cco:designates ) .

# Data
<myObservation678> a cco:ActOfObservation ;
    ex:hasROISpecification <roiSpec123> ;            # Jay's route
    cco:has_output <myImage345> .

<roiSpec123> a ex:RegionOfInterestSpecification ;    # a Directive ICE
    cco:designates <myRegionOfInterest456> .

<myRegionOfInterest456> a cco:GeospatialRegion ;     # a Site; frame: WGS84
    geosparql:hasBoundingBox <Envelope567> .

<myImage345> a ex:ImageContent ;                     # a RICE
    cco:is_about <myRegionOfInterest456> ;           # georeference, known at capture
    cco:represents <materialContents...> .           # added later, if contents are identified

The desired relationship is inferred.

<myObservation678> ex:hasFeatureOfInterest <myRegionOfInterest456> .

Where no specification exists, assert that relation directly. Either way, every query against hasFeatureOfInterest succeeds. This addresses your multi-path point: the long route through the specification and the short route agree, because the axiom makes the first entail the second.

Last,

RegionOfInterest ≡ GeospatialRegion and (ex:isFeatureOfInterestOf some cco:PlannedAct)

I think you should widen GeospatialRegion to a union that includes fiat lines and points.