Six families of inference used by the spatial feature.

§1. Spatial has no fewer than six of its own inference families, needed to store vague indications of spatial structure:

inference_family *is_room_inf = NULL;            is O a room?
inference_family *contains_things_inf = NULL;    does O contain things?
inference_family *parentage_inf = NULL;          where is O located?
inference_family *parentage_here_inf = NULL;     located vaguely as "here"?
inference_family *parentage_nowhere_inf = NULL;  located vaguely as "nowhere"?
inference_family *part_of_inf = NULL;            is O a part of another object?

§2.

void SpatialInferences::create?Usage of SpatialInferences::create:
Spatial Model - §1(void) {
    is_room_inf = Inferences::new_family(I"is_room_inf");
    METHOD_ADD(is_room_inf, EXPLAIN_CONTRADICTION_INF_MTID,
        SpatialInferences::is_room_explain_contradiction);

    contains_things_inf = Inferences::new_family(I"contains_things_inf");

    parentage_inf = Inferences::new_family(I"parentage_inf");
    METHOD_ADD(parentage_inf, LOG_DETAILS_INF_MTID, SpatialInferences::log_parentage_inf);
    METHOD_ADD(parentage_inf, COMPARE_INF_MTID, SpatialInferences::cmp_parentage_inf);
    METHOD_ADD(parentage_inf, EXPLAIN_CONTRADICTION_INF_MTID,
        SpatialInferences::parentage_explain_contradiction);

    parentage_here_inf = Inferences::new_family(I"parentage_here_inf");
    METHOD_ADD(parentage_here_inf, LOG_DETAILS_INF_MTID, SpatialInferences::log_parentage_here);
    METHOD_ADD(parentage_here_inf, COMPARE_INF_MTID, SpatialInferences::cmp_parentage_here);

    parentage_nowhere_inf = Inferences::new_family(I"parentage_nowhere_inf");

    part_of_inf = Inferences::new_family(I"part_of_inf");
    METHOD_ADD(part_of_inf, LOG_DETAILS_INF_MTID, SpatialInferences::log_part_of);
    METHOD_ADD(part_of_inf, COMPARE_INF_MTID, SpatialInferences::cmp_part_of);
}

§3. Details for is_room_inf:

void SpatialInferences::infer_is_room?Usage of SpatialInferences::infer_is_room:
Spatial Model - §5, §24, §25
Spatial Relations - §4.4
Backdrops - §8
The Map - §27
Map Connection Relations - §5(inference_subject *R, int certitude) {
    Inferences::join_inference(
        Inferences::create_inference(is_room_inf, NULL_GENERAL_POINTER, certitude), R);
}

int SpatialInferences::is_room_explain_contradiction?Usage of SpatialInferences::is_room_explain_contradiction:
§2(inference_family *f, inference *A,
    inference *B, int similarity, inference_subject *subj) {
    StandardProblems::two_sentences_problem(_p_(PM_WhenIsARoomNotARoom),
        A->inferred_from,
        "this looks like a contradiction",
        "because apparently something would have to be both a room and not a "
        "room at the same time.");
    return TRUE;
}

§4. Details for contains_things_inf:

void SpatialInferences::infer_contains_things?Usage of SpatialInferences::infer_contains_things:
Spatial Relations - §4.4(inference_subject *R, int certitude) {
    Inferences::join_inference(
        Inferences::create_inference(contains_things_inf,
            NULL_GENERAL_POINTER, certitude), R);
}

§5. Details for parentage_inf:

typedef struct parentage_inference_data {
    struct inference_subject *parent;
    CLASS_DEFINITION
} parentage_inference_data;

void SpatialInferences::infer_parentage?Usage of SpatialInferences::infer_parentage:
Spatial Relations - §4.4
Regions - §18.2(inference_subject *inner, int certitude,
    inference_subject *outer) {
    parentage_inference_data *data = CREATE(parentage_inference_data);
    data->parent = InferenceSubjects::divert(outer);
    inference *i = Inferences::create_inference(parentage_inf,
        STORE_POINTER_parentage_inference_data(data), certitude);
    Inferences::join_inference(i, inner);
}

void SpatialInferences::log_parentage_inf?Usage of SpatialInferences::log_parentage_inf:
§2(inference_family *f, inference *inf) {
    parentage_inference_data *data = RETRIEVE_POINTER_parentage_inference_data(inf->data);
    if (data->parent) LOG(" parent:$j", data->parent);
}

int SpatialInferences::cmp_parentage_inf?Usage of SpatialInferences::cmp_parentage_inf:
§2(inference_family *f, inference *i1, inference *i2) {
    parentage_inference_data *data1 = RETRIEVE_POINTER_parentage_inference_data(i1->data);
    parentage_inference_data *data2 = RETRIEVE_POINTER_parentage_inference_data(i2->data);

    int c = Inferences::measure_infs(data1->parent) -
            Inferences::measure_infs(data2->parent);
    if (c > 0) return CI_DIFFER_IN_CONTENT; if (c < 0) return -CI_DIFFER_IN_CONTENT;

    c = Inferences::measure_inf(i1) - Inferences::measure_inf(i2);
    if (c > 0) return CI_DIFFER_IN_COPY_ONLY; if (c < 0) return -CI_DIFFER_IN_COPY_ONLY;
    return CI_IDENTICAL;
}

int SpatialInferences::parentage_explain_contradiction?Usage of SpatialInferences::parentage_explain_contradiction:
§2(inference_family *f, inference *A,
    inference *B, int similarity, inference_subject *subj) {
    if (SpatialInferences::get_inferred_progenitor(A) !=
        SpatialInferences::get_inferred_progenitor(B)) {
        Problems::quote_source(1, Inferences::where_inferred(A));
        Problems::quote_source(2, Inferences::where_inferred(B));
        Problems::quote_subject(3, subj);
        Problems::quote_object(4, SpatialInferences::get_inferred_progenitor(A));
        Problems::quote_object(5, SpatialInferences::get_inferred_progenitor(B));
        StandardProblems::handmade_problem(Task::syntax_tree(),
            _p_(PM_SpatialContradiction));
        Problems::issue_problem_segment(
            "You wrote %1, but also %2: that seems to be saying that the same "
            "object (%3) must be in two different places (%4 and %5). This "
            "looks like a contradiction. %P"
            "This sometimes happens as a result of a sentence like 'Every person "
            "carries a bag', when Inform doesn't know 'bag' as the name of any "
            "kind - so that it makes only a single thing called 'bag', and then "
            "the sentence looks as if it says everyone is carrying the same bag.");
        Problems::issue_problem_end();
        return TRUE;
    }
    return FALSE;
}

• The structure parentage_inference_data is private to this section.

§6. Details for parentage_here_inf:

typedef struct parentage_here_inference_data {
    struct inference_subject *parent;
    CLASS_DEFINITION
} parentage_here_inference_data;

void SpatialInferences::infer_parentage_here?Usage of SpatialInferences::infer_parentage_here:
Spatial Model - §24(inference_subject *inner, int certitude,
    inference_subject *outer) {
    parentage_here_inference_data *data = CREATE(parentage_here_inference_data);
    data->parent = InferenceSubjects::divert(outer);
    inference *i = Inferences::create_inference(parentage_here_inf,
        STORE_POINTER_parentage_here_inference_data(data), certitude);
    Inferences::join_inference(i, inner);
}

void SpatialInferences::log_parentage_here?Usage of SpatialInferences::log_parentage_here:
§2(inference_family *f, inference *inf) {
    parentage_here_inference_data *data =
        RETRIEVE_POINTER_parentage_here_inference_data(inf->data);
    if (data->parent) LOG(" parent:$j", data->parent);
}

int SpatialInferences::cmp_parentage_here?Usage of SpatialInferences::cmp_parentage_here:
§2(inference_family *f, inference *i1,
    inference *i2) {
    parentage_here_inference_data *data1 =
        RETRIEVE_POINTER_parentage_here_inference_data(i1->data);
    parentage_here_inference_data *data2 =
        RETRIEVE_POINTER_parentage_here_inference_data(i2->data);

    int c = Inferences::measure_infs(data1->parent) -
            Inferences::measure_infs(data2->parent);
    if (c > 0) return CI_DIFFER_IN_CONTENT; if (c < 0) return -CI_DIFFER_IN_CONTENT;

    c = Inferences::measure_inf(i1) - Inferences::measure_inf(i2);
    if (c > 0) return CI_DIFFER_IN_COPY_ONLY; if (c < 0) return -CI_DIFFER_IN_COPY_ONLY;
    return CI_IDENTICAL;
}

• The structure parentage_here_inference_data is private to this section.

§7. Details for parentage_nowhere_inf:

void SpatialInferences::infer_is_nowhere?Usage of SpatialInferences::infer_is_nowhere:
Spatial Model - §25(inference_subject *R, int certitude) {
    Inferences::join_inference(Inferences::create_inference(parentage_nowhere_inf,
        NULL_GENERAL_POINTER, certitude), R);
}

§8. Details for part_of_inf:

void SpatialInferences::infer_part_of?Usage of SpatialInferences::infer_part_of:
Spatial Relations - §4.4
Backdrops - §8(inference_subject *inner, int certitude,
    inference_subject *outer) {
    part_of_inference_data *data = CREATE(part_of_inference_data);
    data->parent = InferenceSubjects::divert(outer);
    inference *i = Inferences::create_inference(part_of_inf,
        STORE_POINTER_part_of_inference_data(data), certitude);
    Inferences::join_inference(i, inner);
}

typedef struct part_of_inference_data {
    struct inference_subject *parent;
    CLASS_DEFINITION
} part_of_inference_data;


void SpatialInferences::log_part_of?Usage of SpatialInferences::log_part_of:
§2(inference_family *f, inference *inf) {
    part_of_inference_data *data = RETRIEVE_POINTER_part_of_inference_data(inf->data);
    if (data->parent) LOG(" part-of:$j", data->parent);
}

int SpatialInferences::cmp_part_of?Usage of SpatialInferences::cmp_part_of:
§2(inference_family *f, inference *i1, inference *i2) {
    part_of_inference_data *data1 = RETRIEVE_POINTER_part_of_inference_data(i1->data);
    part_of_inference_data *data2 = RETRIEVE_POINTER_part_of_inference_data(i2->data);

    int c = Inferences::measure_infs(data1->parent) -
            Inferences::measure_infs(data2->parent);
    if (c > 0) return CI_DIFFER_IN_CONTENT; if (c < 0) return -CI_DIFFER_IN_CONTENT;

    c = Inferences::measure_inf(i1) - Inferences::measure_inf(i2);
    if (c > 0) return CI_DIFFER_IN_COPY_ONLY; if (c < 0) return -CI_DIFFER_IN_COPY_ONLY;
    return CI_IDENTICAL;
}

• The structure part_of_inference_data is private to this section.

§9. Several of those inferences suggest a progenitor, so it's useful to have a single function to return this:

instance *SpatialInferences::get_inferred_progenitor?Usage of SpatialInferences::get_inferred_progenitor:
§5
Spatial Model - §30.3(inference *inf) {
    if (inf->family == parentage_inf) {
        parentage_inference_data *data =
            RETRIEVE_POINTER_parentage_inference_data(inf->data);
        return InstanceSubjects::to_object_instance(data->parent);
    }
    if (inf->family == parentage_here_inf) {
        parentage_here_inference_data *data =
            RETRIEVE_POINTER_parentage_here_inference_data(inf->data);
        return InstanceSubjects::to_object_instance(data->parent);
    }
    if (inf->family == part_of_inf) {
        part_of_inference_data *data =
            RETRIEVE_POINTER_part_of_inference_data(inf->data);
        return InstanceSubjects::to_object_instance(data->parent);
    }
    return NULL;
}