vsm-to-rdf

Overview

This module provides a single function that converts VSM-JSON to RDF Turtle format.
VSM-JSON is the output emitted by a vsm-box web-component, and can be given either as a JSON String or as a not-stringified JS Object.

This module does not check for all possible syntactic errors in the given VSM structure, so any validity checks are the responsibilty of external code.

For an invalid JSON String or some fatal error in the VSM structure, it returns null.

The given VSM data may contain class/inst/parentIDs that are null. Because, when VSM-terms are being created in a vsm-box, they get null as an instID by default (to be filled in e.g. after saving to a database). So support for nulls enables the live inspection of how a VSM-sentence that is being constructed, is translated to a corresponding RDF-structure.
Any null IDs will be replaced by dummy URIs in the RDF output.

For the same reason, the VSM data may contain Edit-type VSM-terms. These are converted to non-Edit ones and are given dummy IDs too.

The VSM ontology: mapping VSM semantics to RDF

i. Intro

This module uses the VSM Ontology (VSMO) [to be created], which provides 'primitive relations' that define how VSM-connectors link VSM-terms together in an RDF-representation.

Note that in contrast, 'real relations' in a VSM-sentence are represented not by Properties but by Classes/Instances in RDF. This is similar to RDF's n-ary relations, pattern 1, but:

1. every relation is modeled by applying this n-ary pattern, iteratively, until only primitive relations like "has subject" and "has object" remain; and
2. relations that in essence represent a primitive relation are not represented with redundant specificity, which means that e.g. "buying-action has-buyer X" is just modeled as "buying-action has-subject X".

VSMO's small set of primitive relations (or framework-only relations) make the semantics of VSM-connectors explicit in RDF.

VSMO's URIs have the prefix http://www.w3id.org/vsmo/, which we will denote by vsmo:.

The text below elaborates some of VSM's semantics in detail, which is necessary to correctly interpret the semantics of the corresponding RDF-representation.

ii. VSMO primitive relations

VSMO defines the following primitive relations, as Instances of rdf:Property:

• For the trident VSM-connector:
  • vsmo:has-agent: represents the "has-subject" part in RDF, connecting the relation term to the subject term.
    (Note that if the name "has-subject" would be used, it might lead to confusion with "rdf:subject", which is used in RDF reification (a different pattern to represent relations, distinct from the n-ary pattern)).
  • vsmo:acts-on: represents the "has-direct-object" part in RDF, connecting the relation term to the direct-object term.
    (A similar note as above can be made regarding "rdf:object").
    (Note also that although an alternative name "has-patient" could be used here (which is typically used together with "has-agent" elsewhere), the term "patient" might lead to confusion in VSM's first application domains: biology and medicine).
• For a list-connector:
  this is represented in RDF with the primitive relations:
  • vsmo:has-first-element: which connects the VSM list-relation to its first list-element, and:
  • vsmo:has-next-element: which connects each list-element to the next one, creating an ordered sequence.
  • Note that the order in which list-elements appear in both VSM-JSON and RDF only carries 'real' meaning (i.e. has semantic relevance), when the list-relation assigns meaning to the order of its list-elements, as defined in the spec.
• For a coreference:
  its RDF representation uses
  • vsmo:has-parent: which aims to model the connection of a 'child' VSM-term to a 'parent' VSM-term.
  • Note that, as defined in the spec, a child and a parent VSM-term both represent the same 'thing' in the real world, but at different stages of 'explicit context' being attached to it.
  • Note: explicit context = all the specificity in meaning that a VSM-Instance or VSM-RefInstance term receives through trident and list-relation connections (regardless of leg/role) with other VSM-terms.
    For RefInstance terms, this comes in addition to (and may supersede meaning of): any other specificity in meaning that it receives from its parent VSM-term, (which receives its explicit context in the same way).
    This comes again in addition to any prototype-descriptions that the Ref/Instance's parent VSM-Class may be linked to (e.g. "Duck(in general) sometimes quaks").
  • Note: implicit context = all the not or not yet defined explicit context. This includes everything unsaid or unknown about it, and that also make this Ref/Instance a 'specific' thing or concept, plus everything that could ever still become knowable or explicitly stated about it.
    A reasoning system could make use of this principle, by for example temporarily adding assumptions about the implicit context (temporarily modeled as explicit context), during a reasoning process.

    (Note that this illustrates that the purpose of VSM is not to model reality directly, but to support a 'thinking' process that aims to model reality and its unknowns, in an intuitive and expressive way).

  • Therefore, the meaning of vsmo:has-parent is: the copying of specifics or meaning that is captured in explicit context, from a parent onto a child.
  • Also therefore in RDF, the parent and child should not be merged into one node.

    It remains to be investigated how this essential concept of VSM could be mapped precisely in terms of BFO.

iii. VSMO Classes

VSMO defines the following Classes, as Instances of rdfs:Class:

• vsmo:ActiveRelation:
  Each term used as a relation in a VSM-sentence, is in RDF modeled by an Instance, which could be inferred to be instance of the ActiveRelation Class.
  • (Note that if we would just name this vsmo:Relation, it might lead to confusion with RDF's rdf:Relation).
• vsmo:HasQuality:
  A relation-omitting bident's implicit relation is in RDF modeled by a blank node that is an instance of this class.
  This class is a specialization of vsmo:ActiveRelation, as it plays the same role between a subject and an object term.

iv. --- Critical remarks ---

• On vsmo:acts-on:
  
  • The name "acts-on" may be too specific, compared to just "has-patient" or "has-object".
    For example "duck is-located-in pond" would be converted to "being-located has-subject duck' + 'being-located acts-on pond", even though this relation expresses no real activity.
  • VSM is designed for use beyond the biosciences, which weakens an argument that the alternative name "has-patient" would lead to confusion in general.
• On vsmo:has-agent:
  
  • "has-agent" is probably not the correct term for "has-subject".
    Look at the example mentioned here: "girl is-bitten-by dog".
    While girl is the subject, it is not the agent. Instead dog is the grammatical agent.
    But in VSM, girl is the subject of this triple of terms, and must be assigned as such by a trident subject-leg. (So here, "is-bitten-by" is a passive relation, which has as semantic inverse the "bites" relation).
    VSM connectors are designed to assign terms' syntactic role, from which semantics can be inferred. In a proper bridge between human and computer thinking, forcing people to think about a less intuitive "agent" meaning (which would only be reached after an extra step of thinking), would be poor design; especially when it can be automatically inferred.
    Also, the existence of inverse relations that are both not-passive, like "precedes" and "follows", suggests that inverse-inference should be part of a suitable reasoner anyway.
• On vsmo:HasQuality:
  
  • The 'implicit relation' of relationless bidents is meant to be used with more than just BFO-Quality terms. It can connect any two terms for which a particular relation can be inferred, as demonstrated in the spec.
    Therefore it may be better to name it vsmo:HasAttribute instead.
  • In fact, no semantically 'real' HasAttribute (Active)relation is inserted by a relation-omitting bident, just like a trident does not insert a 'real' HasSubject/HasObject relation.
    Therefore it might be more consistent to more closely preserve the original structure and instead model this with a vsmo:has-attribute primitive in RDF, that directly connects the subject to the object term.
    And perhaps(?) this makes it simpler in RDF, to write rules that infer intended, explicit relations between subject and object, because the rules would not need to match an extra inserted HasAttribute blank node.
• On vsmo:ActiveRelation:
  
  • This is probably a too specific name. For example "to-be-located-in" is not a real activity.
    But, just using a name vsmo:Relation might lead to confusion with rdf:Relation.
    So perhaps we could follow Hans Teijgeler's tentative approach and name it vsmo:Relationship.
• Furthermore:
  • All has- prefixes could be dropped for simplicity (as it is done for relations that support RDF reification).
    So the proposal is to use: vsmo:subject, vsmo:object, etc.
  • Going this far already, why not simply dropping the o from vsmo as well? Then it becomes more fluent in conversations, when talking and making a distinction between rdf:subject versus vsm:subject, etc. And there is no rdfo:/owlo: with an o etc either.
  • Going further along this line, now vsm:Relation sounds justifiable again.
    Because: it is a defining feature of VSM, that it treats entities and relations equally. So anyone using vsm:-terms properly would at least have to know that all real relations in VSM are modeled with RDF Classes, and only the few primitive ones as Properties.
• So the final proposal is:
  1. to keep names simple in the VSM ontology:
     • vsmo:has-agent -> vsm:subject
     • vsmo:acts-on -> vsm:object
     • vsmo:HasQuality -> vsm:attribute
     • vsmo:has-first-element -> vsm:first
     • vsmo:has-next-element -> vsm:next
     • vsmo:has-parent -> vsm:parent
     • vsmo:ActiveRelation -> vsm:Relation
  2. to include all the above reasons and critical remarks around possible other namings, as a permanent reference in this repository here (after some reformatting);
  3. to recommend that people add the 'vsm:' prefix in their writings and conversations, when things might be confused with RDF or OWL.

Specification of the conversion to RDF

1. VSM-terms

1.1. Pre-processing of null-IDs

Note that:

• VSM-terms of the type VSM-Class, -Instance, or -RefInstance (note: these are not RDF types) have a classID property in the VSM-JSON;
• VSM-terms of the type VSM-Instance or -RefInstance have an instID property too;
• VSM-terms of the type VSM-RefInstance have a parentID property too.

Each of these IDs should be either a URI or null in the input VSM-JSON.

• For any classID or instID that is null: this module first generates a dummy URI.
• For any parentID that is null, for a term that is not connected by a coreference as child term to a parent term: this module generates a dummy URI (which would represent a referred-to instID in some other VSM-sentence).
• For any parentID that is null, for a term that is connected by a coreference as child term to a parent term (i.e. in the same VSM-sentence): this module makes the child's parentID equal to its parent's instID, and the child's classID equal to its parent's (after any parent null IDs are replaced by dummy URIs).

1.2. Generation of RDF for VSM-terms

For each VSM-Instance or -RefInstance term, a line like this is added to the output RDF:

{instID} a {classID} .

For VSM-Class or -Literal terms, no such line is added.

A VSM-Literal term is represented by the following fragment, wherever it occurs: "{literal-text}"^^xsd:string.

For each VSM-RefInstance term that is not connected by a coreference as the child term, (and thus refers to an VSM-Instance term in another VSM-sentence), the external reference is made explicit, by adding two lines like this:

{parentID} a {classID} .
{instID} vsmo:has-parent {parentID} .

2. VSM-connectors

Here we show the RDF-representation of VSM-connectors. Note:
• the examples use {Role-instID} to represent a connected VSM-term, because VSM-Ref/Instance terms (which have an instID) are the most common ones;
• for a connected VSM-Class term, this would be replaced by {Role-classID};
• for a connected VSM-Literal term, this would be replaced by "{literal-text}"^^xsd:string.

2.1. Trident

A trident connects three VSM-terms and assigns to each either the Subject, Relation, or Object role, relative to the other two.
For each trident, a line like this is added:

{Relation-instID} vsmo:has-agent {Subject-instID} ; vsmo:acts-on {Object-instID} .

2.2. Object-omitting Bident

Bidents are just subtypes of the trident, with the same semantics.
The object-omitting bident is used to model phrases with a verb that has no object, like "device explodes". For these bidents, a line like this is added:

{Relation-instID} vsmo:has-agent {Subject-instID} .

2.3. Subject-omitting Bident

The subject-omitting bident models phrases where the subject is irrelevant or not given, as in "destruction(-of) X", or "to-write book". For these bidents, a line like this is added:

{Relation-instID} vsmo:acts-on {Object-instID} .

2.4. Relation-omitting Bident

The relation-omitting bident models an association between a Subject and an Object term, whereby an implicit relation "HasQuality" is implied.
For example, "white mouse" is mapped to "mouse HasQuality white". (Note that a reasoner could infer a more specific "HasColor" from this, if "white" is an instance of "Color" in its source ontology).
For these bidents, a blank node is generated for the implicit relation (as it has no identifier in the VSM-JSON), and a line like this is added:

[a vsmo:HasQuality] vsmo:has-agent {Subject-instID} ; vsmo:acts-on {Object-instID} .

2.5. List-connector

This connects a list-relation and N (>0) list-elements. For a list-connector, a series of lines like this is added:

{ListRelation-instID} vsmo:has-first-element {ListElement-1-instID} .
{ListElement-1-instID} vsmo:has-next-element {ListElement-2-instID} .
...
{ListElement-(N-1)-instID} vsmo:has-next-element {ListElement-N-instID} .

2.6. Coreference connector

This connects a child term to a parent term, with semantics as described earlier. For a coreference, a line like this is added:

{Child-instID} vsmo:has-parent {Parent-instID} .

Example conversions

In the examples below, we use example URIs for classes and example database identifiers for instances.
(Tip: you can paste VSM-JSON in a textfield on scicura.org/vsm-box, and see/edit it in a vsm-box).

E1. Simple example

The following piece of information is represented with just two tridents:

John eats chicken with fork.

• In a vsm-box (screenshot):

• As VSM-JSON (written in not-serialized, JS-Object form):

{
  terms: [
    { str: 'John',    classID: 'http://ont.ex/John',    instID: 'http://db.ex/00' },
    { str: 'eats',    classID: 'http://ont.ex/to-eat',  instID: 'http://db.ex/01' },
    { str: 'chicken', classID: 'http://ont.ex/chicken', instID: 'http://db.ex/02' },
    { str: 'with',    classID: 'http://ont.ex/to-use',  instID: 'http://db.ex/03' },
    { str: 'fork',    classID: 'http://ont.ex/fork',    instID: 'http://db.ex/04' }
  ],
  conns: [
    { type: 'T', pos: [ 0, 1, 2 ] },
    { type: 'T', pos: [ 1, 3, 4 ] }
  ]
}

• As RDF Turtle:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX vsmo: <http://www.w3id.org/vsmo/>

http://db.ex/00 a http://ont.ex/John .
http://db.ex/01 a http://ont.ex/to-eat .
http://db.ex/02 a http://ont.ex/chicken .
http://db.ex/03 a http://ont.ex/to-use .
http://db.ex/04 a http://ont.ex/fork .

http://db.ex/01 vsmo:has-agent http://db.ex/00 ; vsmo:acts-on http://db.ex/02 .
http://db.ex/03 vsmo:has-agent http://db.ex/01 ; vsmo:acts-on http://db.ex/04 .

E2. Example with the four VSM-term types, and some null IDs

John saying that ducks (in general) are called 'canard' (as a label), implies that he (=John) knows French.

• In a vsm-box (screenshot):

• As VSM-JSON:

{
  terms: [
    { str: 'John',      classID: 'http://ont.ex/John',          instID: null },
    { str: 'saying',    classID: 'http://ont.ex/to-say',        instID: null },
    { str: 'duck',      classID: 'http://ont.ex/duck'                        },  // Class
    { str: 'has-label', classID: 'http://ont.ex/to-have-label', instID: null },
    { str: 'canard'                                                          },  // Literal
    { str: 'implies',   classID: 'http://ont.ex/to-imply',      instID: null },
    { str: 'he',        classID: 'http://ont.ex/John',          instID: null, parentID: null },  // RefInstance
    { str: 'knows',     classID: 'http://ont.ex/to-know',       instID: null },
    { str: 'French',    classID: null,                          instID: null }   // =request to create new Class.
  ],
  conns: [
    { type: 'T', pos: [ 2, 3, 4 ] },
    { type: 'T', pos: [ 0, 1, 3 ] },
    { type: 'T', pos: [ 6, 7, 8 ] },
    { type: 'T', pos: [ 1, 5, 7 ] },
    { type: 'R', pos: [ 6, 0 ] }
  ]
}

• As RDF Turtle:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX vsmo: <http://www.w3id.org/vsmo/>

http://inst.x/00 a http://ont.ex/John .
http://inst.x/01 a http://ont.ex/to-say .
http://inst.x/03 a http://ont.ex/to-have-label .
http://inst.x/05 a http://ont.ex/to-imply .
http://inst.x/06 a http://ont.ex/John .
http://inst.x/07 a http://ont.ex/to-know .
http://inst.x/08 a http://class.x/08 .

http://inst.x/03 vsmo:has-agent http://ont.ex/duck ; vsmo:acts-on "canard"^^xsd:string .
http://inst.x/01 vsmo:has-agent http://inst.x/00 ; vsmo:acts-on http://inst.x/03 .
http://inst.x/07 vsmo:has-agent http://inst.x/06 ; vsmo:acts-on http://inst.x/08 .
http://inst.x/05 vsmo:has-agent http://inst.x/01 ; vsmo:acts-on http://inst.x/07 .
http://inst.x/06 vsmo:has-parent http://inst.x/00 .

E3. Example with all connectors

The following example contains several tridents, two types of bident, a list connector, and a coreference connector:

John pushes a green colored button, causing it to be colored red and a tiny bomb to explode.

• In a vsm-box (screenshot):

• As VSM-JSON:

{
  terms: [
    { str: 'John',          classID: 'http://ont.ex/John',          instID: 'http://db.ex/00' },
    { str: 'pushes',        classID: 'http://ont.ex/to-push',       instID: 'http://db.ex/01' },
    { str: 'button',        classID: 'http://ont.ex/button',        instID: 'http://db.ex/02' },
    { str: 'having color',  classID: 'http://ont.ex/to-have-color', instID: 'http://db.ex/03' },
    { str: 'green',         classID: 'http://ont.ex/green',         instID: 'http://db.ex/04' },
    { str: 'causing',       classID: 'http://ont.ex/to-cause',      instID: 'http://db.ex/05' },
    { str: 'it',            classID: 'http://ont.ex/button',        instID: 'http://db.ex/06', parentID: 'http://db.ex/02' },
    { str: 'to have color', classID: 'http://ont.ex/to-have-color', instID: 'http://db.ex/07' },
    { str: 'red',           classID: 'http://ont.ex/red',           instID: 'http://db.ex/08' },
    { str: 'and',           classID: 'http://ont.ex/and',           instID: 'http://db.ex/09' },
    { str: 'tiny',          classID: 'http://ont.ex/tiny',          instID: 'http://db.ex/10' },
    { str: 'bomb',          classID: 'http://ont.ex/bomb',          instID: 'http://db.ex/11' },
    { str: 'to explode',    classID: 'http://ont.ex/to-explode',    instID: 'http://db.ex/12' }
  ],
  conns: [
    { type: 'T', pos: [ 2, 3, 4 ] },
    { type: 'T', pos: [ 0, 1, 2 ] },
    { type: 'T', pos: [ 6, 7, 8 ] },
    { type: 'T', pos: [ 11, -1, 10 ] },
    { type: 'T', pos: [ 11, 12, -1 ] },
    { type: 'L', pos: [ 9, 7, 12 ] },
    { type: 'T', pos: [ 1, 5, 9 ] },
    { type: 'R', pos: [ 6, 2 ] }
  ]
}

• As RDF Turtle:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX vsmo: <http://www.w3id.org/vsmo/>

http://db.ex/00 a http://ont.ex/John .
http://db.ex/01 a http://ont.ex/to-push .
http://db.ex/02 a http://ont.ex/button .
http://db.ex/03 a http://ont.ex/to-have-color .
http://db.ex/04 a http://ont.ex/green .
http://db.ex/05 a http://ont.ex/to-cause .
http://db.ex/06 a http://ont.ex/button .
http://db.ex/07 a http://ont.ex/to-have-color .
http://db.ex/08 a http://ont.ex/red .
http://db.ex/09 a http://ont.ex/and .
http://db.ex/10 a http://ont.ex/tiny .
http://db.ex/11 a http://ont.ex/bomb .
http://db.ex/12 a http://ont.ex/to-explode .

http://db.ex/03 vsmo:has-agent http://db.ex/02 ; vsmo:acts-on http://db.ex/04 .
http://db.ex/01 vsmo:has-agent http://db.ex/00 ; vsmo:acts-on http://db.ex/02 .
http://db.ex/07 vsmo:has-agent http://db.ex/06 ; vsmo:acts-on http://db.ex/08 .
[a vsmo:HasQuality] vsmo:has-agent http://db.ex/11 ; vsmo:acts-on http://db.ex/10 .
http://db.ex/12 vsmo:has-agent http://db.ex/11 .
http://db.ex/09 vsmo:has-first-element http://db.ex/07 .
http://db.ex/07 vsmo:has-next-element http://db.ex/12 .
http://db.ex/05 vsmo:has-agent http://db.ex/01 ; vsmo:acts-on http://db.ex/09 .
http://db.ex/06 vsmo:has-parent http://db.ex/02 .

License

This project is licensed under the AGPL license - see LICENSE.md.