=Paper=
{{Paper
|id=None
|storemode=property
|title=Representing Deontic Concepts for CNLs
|pdfUrl=https://ceur-ws.org/Vol-622/paper15.pdf
|volume=Vol-622
}}
==Representing Deontic Concepts for CNLs==
https://ceur-ws.org/Vol-622/paper15.pdf
Representing Deontic Concepts for CNLs
Adam Wyner
Centre for Digital Citizenship, Institute for Communication Studies, University of Leeds.
E-mail: adam@wyner.info
1 Introduction
The deontic concepts, obligation, permission, and prohibition, express what an individ-
ual ought to do, may do, or should not do; they ascribe a property to an action that an
individual or collective performs, what we refer to here as deontic specifications. For
brevity, we focus on obligation. We can say that the purpose of the concepts is to help
the agent to guide his behaviour in the sense that the agent prospectively considers the
consequences of his actions relative to some deontic ascription to an action, where the
consequences follow from the fulfillment or violation of the obligation. The nature of
the deontic concepts is that violations may arise, but we can reason with them.
For controlled natural languages (CNLs), it would be useful to be able to write deon-
tic specifications for legal documents. However, to create a CNL with deontic concepts,
one must address a range of unusually complex and as yet unresolved issues in natural
language syntax and semantics ([1], [2] and [3]).
In this paper, we outline some key points from [4], which discusses the natural lan-
guage syntax and and formal semantics of deontic concepts. This presentation serves as
a high level departure point and framework for CNLs which aim to extend the expres-
sivity of the language to the deontic concepts. While this paper does not itself present
novel research, it is nonetheless novel and relevant to the CNL research community.
2 Linguistic Considerations
The wide-range of problems and issues found in the literature must be considered in the
requirements analysis for the design of a CNL with deontic concepts. In many deontic
logics, the deontic concepts are represented as sentential modal operators syntactically
and semantically analogous to alethic modal operators Necessity and Possibility. How-
ever, the analogy gives rise to numerous problems. We argue that some of the issues
can be addressed by making linguistically well-grounded observations and adopting
linguistic theories. Some key bullet points are:
– Modal operators such as “ought” in Bill ought to have left by now have epistemic
and non-epistemic interpretations, where the former has a quantificational meaning
(in most contexts what happens), while the latter has a meaning where violation and
fulfillment arise. We are primarily interested in the non-epistemic interpretation.
– A range of logical paradoxes arise, where the paradoxes are counter-intuitive infer-
ences which arise from a the logical representation of a set of sentences such as Bill
ought to leave the house. If Bill leaves the house, then Bill ought to visit Jill. If Bill
doesn’t leave the house, then Bill ought not to visit Jill. Bill leaves the house. We
argue that the deontic operators have a restricted semantic distribution.
– Two specific forms of the paradoxes, the Gentle Murderer Paradox and the Good
Samaritan Paradox, can be can resolved by applying linguistic theory – focus, ad-
verbial semantics, discourse representation, and generalised quantifiers.
– Deontic operators on stative expressions and agentive actions are distinguished,
where statives ought to be analysed to have an implicit agentive action.
– Temporal operators and deadlines are often claimed to be intrinsic to an analysis of
the deontic operators [5]. We argue they are not, but rather they are one of a number
of interactions between operators of different sorts.
– Action negation should be construed in lexical semantic terms as antonyms, allow-
ing some actions to be undefined with respect to obligation.
3 Theoretical Development
We base our analysis on a modal action logic [6, 7], where the deontic operators are
reduced to actions and violation/fulfillment markers. Novel to our approach, the mark-
ers are fine-grained, complex expressions that are compositionally derived from the
expression the operator applies to. We focus the discussion on the difference between
sequences of obligations in contrast to obligations on sequences. The problem illus-
trates a general point that deontic operators are sensitive to the fine-grained linguistic
structure of the expression they apply to.
We briefly review the proposal for the purposes of the abstract. In modal action
logics, actions are state-changing functions. Given an action name α and a proposition
φ, we may form the proposition [α]φ. Where an action is executed (the preconditions
are satisfied), it results in a state in which the postconditions, whatever they are, hold
along with φ. The negation of an action α, α, denotes the complement set relative to α
[8]. Complex action combinators puts two actions in sequence ‘;’.
Deontic operators apply directly to action names of atomic or complex actions. They
are reduced to actions and a violation marker V
σ |= OBα iff [α](V)
It is obligatory to do α in σ iff doing anything other than α leads to a violation.
However, the single marker of violation does not make any fine-grained distinctions,
though these parameters can be added. A key point of this approach is that violation
leads to a state marked as having a property V rather than being false. Thus, the agent
can reason with respect to the violation rather than ruling out such circumstances as is
the case with static system constraints.
In our analysis, the markers are formal analogs to the natural language expressions.
a. Bill is obligated to move the left toggle up.
b. Were Bill to move the left toggle down, there is a violation of an obligation with
respect to Bill on the movement of the left toggle up. Were Bill to move the left tog-
gle up, there is a fulfillment of an obligation with respect to Bill on the movement
of the left toggle up.
We decompose the verbal form of obligation into a correlated nominal form which
expresses violation and fulfillment. In other words, there is an abstract object with the
requisite properties (similar to [9]).
To formalise the analysis, we postulate several sorts of abstract objects along with
functions to relate them. We give an example and describe it. The nominal portion of
the deontic specification is:
∃ x ∈ DS [deonticOpF(x) = “obligation” ∧ actionF(x) = “α” ∧ agentF(x) = “Bill” ∧
deonticFlagF(x) = “violation”].
There is a deontic specification x which has as deontic operator the “obligation”, the
action “α”, the agent “Bill”, and the deontic marker “violation”.
Where α is executed, this “flag” arises; where α is executed, a fulfillment “flag” arises.
On complex actions such as sequences, we have several alternative definitions. We
provide the collective interpretation of“It is obligatory that Bill move the left toggle up,
and then Bill move the right toggle left.” Here, the deontic operator applies to the se-
quence itself as in a procedure; the consequences of violating the procedure are distinct
from those which follow from violating any one action which comprise the procedure.
OBcoll ((α;β),ι) =def
[α; β](∃ds3 (deonticOpF(ds3) = “obligation” ∧ actionF(ds3) = “α;β” ∧ agentF(ds3)
=“ι” ∧ deonticFlagF(ds3) = “violation”)) ∧
[α; β](∃ds4 (deonticOpF(ds4) = “obligation” ∧ actionF(ds4) = “α; β” ∧ agentF(ds4) =
“ι” ∧ deonticFlagF(ds4) = “fulfillment”))
We must give a generative definition of action antonym for complex actions (see [4]).
The language is highly flexible and extensible. While the theoretical development
focused on issues bearing on sequences of actions, which in turn supports an analysis
of a key Contrary-to-Duty Paradox.
With respect to CNLs, the translation of deontic specifications now takes on the
flavour of a translation to event-theoretic semantics [9]. The main challenge is to con-
strue the actions as dynamic, context-changing functions.
4 Discussion
The literature on the deontic concepts is very extensive. We have not defended our
position with respect to the many varieties. We remark on one particular line of research
stemming from the Event Calculus [10], [11], [12]; these are rich systems which clearly
warrant further development. Given our analysis of violations and fulfillments, it may be
rather straightforward to express them in these logics (suitably extended and modified).
We did not adopt these approaches since (depending on the approach) they did not take
into account: Contrary-to-Duty Paradoxes, constraints on deontic operators, statives,
complex violation and fulfillment markers, deontic operators on complex actions, and
action negation as lexical semantics. Nor did we adopt theories where temporality is
central [12]. [13] is a recent effort to incorporate deontic concepts into a CNL with an
Event Calculus. However, it also does not address these issues and contains no violation
markers, but has a semantics with truth values; deadlines are assumed to be central.
Our approach must provide notions of interdefinability of the expressions with the
operators, consistency among them, nor implication from them. However, this is not
an issue unique to our proposal, but is a common problem [8]. Indeed, the paradoxes
arise due to over-generation, which does not occur in our approach. Moreover, we could
impose ’meaning postulates’ to account for relevant properties in a more ’local’ sense.
We have not, in this short overview, outlined the implementation. It should be noted
that the implementation is designed to address the issue of obligations on sequences and
the related Contrary-to-Duty paradoxes. It includes a detailed, but abstract development
of the lexical semantics of antonyms for abstract actions comprised of explicit pre and
post conditions. Whether actions from natural language can be reduced in such a way
is an open question. [4] also includes a range of other topics such as contract updates.
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