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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>What are you thinking? Explaining conversational agent responses for criminal investigations</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Sam Hepenstal</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Neesha Kodagoda</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Leishi Zhang</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>B. L. William Wong</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Defence Science Technology Laboratory</institution>
          ,
          <country country="UK">UK</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Middlesex University London</institution>
          ,
          <country country="UK">UK</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2020</year>
      </pub-date>
      <abstract>
        <p>The adoption of complex artificial intelligence (AI) systems in environments that involve high risk and high consequence decision making is severely hampered by critical design issues. These issues include system transparency which covers (i) the explainability of results and (ii) the ability of a user to inspect and verify system goals and constraints. We present a novel approach to designing a transparent conversational agent (CA) AI system for information retrieval to support criminal investigations. Our method draws from Cognitive Task Analysis (CTA) interviews to inform the system architecture, and Emergent Themes Analysis (ETA) of questions about an investigation scenario, to understand the explanation needs of diferent system components. Furthermore, we implement our design approach to develop a preliminary prototype CA, named Pan, which demonstrates transparency provision. We propose to use Pan for exploring system requirements further in the future. Our approach enables complex AI systems, such as Pan, to be used in sensitive environments introducing capabilities which otherwise would not be available.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>CCS CONCEPTS</title>
      <p>• Computer systems organization
puting.</p>
    </sec>
    <sec id="sec-2">
      <title>INTRODUCTION</title>
      <p>
        Artificial intelligence (AI) based conversational agent (CA)
technologies are complex systems which are increasing in popularity
[
        <xref ref-type="bibr" rid="ref5 ref6">5, 6</xref>
        ], because they provide more intuitive, natural, and faster
access to information. They could benefit criminal investigations,
where repeated information retrieval tasks are performed by
analysts and the volume of data that requires filtering and processing
is significant. In June 2019 Cressida Dick, the Commissioner of the
Metropolitan Police, explained that “sifting through vast amounts
of phone and computer data is partly to blame (for low solved crime
rates) as it slows down investigations”[
        <xref ref-type="bibr" rid="ref16">16</xref>
        ]. A more natural
interaction, which removes the requirement for analysts to translate
their questions into restrictive syntax or structures, could speed up
this process significantly. If an analyst were able to communicate
with their data in the same way as they do with their colleagues,
through natural language, then they could achieve significant time
savings and speed up investigations.
      </p>
      <p>
        However, for complex applications to be used in high risk and
high consequence domains, transparency is crucial. If an analyst
misinterprets system processes and information caveats when
retrieving information in a live investigation then the impacts can be
serious, for example leading to errors such as directing resources
to the wrong location, or failing to find a vulnerable victim.
Misinterpretation is a particular risk where there are subjectivities,
such as when using a CA to interpret human intentions. We define
transparency as the ease with which a user can (i) explain results
provided by a system, in addition to (ii) being able to inspect and
verify the goals and constraints of the system within context [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
Without transparency, including appropriate levels of audit,
complex systems cannot be used by intelligence analysts to support
their investigations.
      </p>
      <p>
        The domain of intelligence analysis is broad and diverse,
therefore we have focused upon a narrow spectrum of criminal
intelligence analysis and information retrieval tasks. To develop the
prototype we first gathered and analysed data from CTA interviews
with operational police analysts to identify the way they recognise,
construct, and develop their questioning strategies in an
investigation. We captured important attributes within the interview data
linked to the Recognition-Primed Decision (RPD) model [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] and
applied Formal Concept Analysis (FCA), a mathematical method
to transform question objects and associated functional attributes
into lattice structures, to identify intention concepts (contribution
1). We can therefore provide an explanation structure for each
intention, and the underlying system processes, which mirrors the
way in which humans recognise situations. We propose that this
approach enhances the ability to inspect system behaviour and
deliver transparency.
      </p>
      <p>We also present findings from scenario based interviews with a
diferent set of operational analysts. In these we looked to identify
what information is required in explanations of the various
components that form a CA. The interview data is distilled to distinct
statements made by the analysts and further refined using
Emergent Themes Analysis (ETA), to form an explanation framework
covering CA system components (contribution 2). We describe a
novel CA prototype, named Pan, (contribution 3) designed to
address transparency issues, using our findings from the two sets of
interviews.</p>
      <p>The work discussed in this paper provides a preliminary
investigation of transparency issues for information retrieval with complex
systems, in the specific domain of criminal investigations. In
future work we plan to probe further and to evaluate the prototype
through experimentation with intelligence analysts.
2</p>
    </sec>
    <sec id="sec-3">
      <title>RELATED WORK</title>
      <p>
        Analysts play an important role in criminal investigations, as the
results of their analysis underpins decision making by police
commanders. For example, intelligence analysis directs the prioritisation
of lines of inquiry in an investigation and assessments of key
suspects. The process of intelligence analysis involves repetitive and
intellectually non-trivial information retrieval tasks where “each
piece of insight leads to intense periods of manual information
gathering”[
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. For example, if a new lead is provided about a
suspicious vehicle, analysts would ask questions such as ‘who owns
the vehicle?’ and ‘is the vehicle linked to any previous incidents?’
If an intelligent system can improve this process the impact could
be significant.
      </p>
      <p>Manual formulation of query syntax or interactions with
traditional analysis tools can be cumbersome and time consuming.
A more natural interaction, which removes the requirement for
analysts to translate their questions into restrictive syntax or
structures, could speed up this process significantly. If an analyst were
able to communicate with their data in the same way as they do
with their colleagues, through natural language, then they could
achieve significant time savings and speed up investigations.</p>
      <p>
        We define typical CAs as being able to understand users by
matching their input pattern to a particular task category
(intention), for example through ‘Artificial Intelligence Markup Language’
(AIML) [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ], where the intention triggers a set of functional
processes. For banal tasks, such as playing a music playlist, the risks
of an incorrect or misleading response are low and the resulting
consequences limited. As a result, traditional CAs have not been
built with algorithmic transparency in mind. If you ask Google
Assistant, for example, why it has provided a particular response it
will not be able to tell you and instead responds with humour, such
as ‘Let’s let mysteries remain mysteries.’ This is not appropriate
for use in criminal investigations where decisions can have serious
impact, for example to direct resources towards the wrong suspect.
2.1
      </p>
    </sec>
    <sec id="sec-4">
      <title>Criminal investigations need explaining</title>
      <p>
        Some research to date has touched on the need for a CA to be
able to explain its responses. Preece et al. describe the ability to
ask a CA ‘why’ they have provided a particular response, so an
analyst can obtain the agent’s rationale. An explanation could be
“a summary of some reasoning or provenance for facts”[
        <xref ref-type="bibr" rid="ref13">13</xref>
        ]. This
understanding of explanation is consistent with research into
explainable machine-learning, where the focus is placed upon the
specifics of the data retrieved, or the internals of a model. Gilpin
et al. [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ], defines eXplainable AI (XAI) as a combination of
interpretability and completeness, where interpretability is linked to
explaining the internals of a system and completeness is to describe
it as accurately as possible.
      </p>
      <p>
        Intelligence analysis is a field where analysts operate in complex,
subjective, uncertain and ambiguous environments, and a simple
explanation of the data or a model which defines a response is not
enough to satisfy their needs for understanding. For example, if
the method applied by the system presents significant constraints
of which the analyst is not aware. Previous research has looked
at this issue and developed a design framework for algorithmic
transparency [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. This describes the necessity to go beyond XAI
when designing intelligent systems, to include visibility of the
system goals and constraints within context of the situation. Context
relates to the usage and user, including a user’s mental model for
the ways in which the CA system works. Users who have a
different mental model to the realities of the system can encounter
dificulties and are prone to error [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ].
2.2
      </p>
    </sec>
    <sec id="sec-5">
      <title>Structuring Human-Machine Recognition</title>
      <p>
        In a policing scenario, when an analyst is presented with a situation
they immediately look to make sense of it. They apply experience
to recognise aspects of the situation and construct a plausible
narrative explanation with supporting evidence. Klein [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] presents
the Recognition-Primed Decision (RPD) model to characterise how
humans recognise and respond to situations, including their cues,
expectancies, actions and goals. The RPD model was first developed
to understand how experienced people can make rapid decisions
using a case study on fire ground commanders, another high risk
and high consequence domain.
      </p>
      <p>We desire a CA that can recognise situations in a similar
fashion and respond to analyst questions appropriately. We also need
analysts to recognise the behaviour of a CA in each situation when
it attempts to understand and respond to the analyst. We propose
that the RPD model provides a useful foundation to designing CA
intentions so a CA can recognise analyst inputs, in addition to an
explanation structure so that its behaviour can also be recognised
and understood by the analyst.
3
3.1</p>
    </sec>
    <sec id="sec-6">
      <title>MODELLING CA INTENTIONS</title>
    </sec>
    <sec id="sec-7">
      <title>Participants and Method</title>
      <p>
        We conducted Cognitive Task Analysis (CTA) interviews, applying
the Critical Decision Method [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ], with four intelligence analysts to
delve into a particularly memorable incident for each. The analysts
have a minimum of 5 years operational experience. In this study, we
analyse interview data to identify the thought processes of analysts,
including the questions they asked during their investigations and
requirements for responses.
3.2
      </p>
    </sec>
    <sec id="sec-8">
      <title>Analysis and Results</title>
      <p>
        For each interview we attempted to understand how analysts
identified what was happening and the information they needed to
advance their investigations. Critical to this process is how analysts
recognise and respond to situations. We analysed analyst interview
statements, structuring them against the Recognition-Primed
Decision (RPD) model [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ], and found that the model is appropriate to
capture and explain their processing of information in an
investigation (Table 1). We propose that the RPD model, therefore, provides
Transcript Statement [CTA: A1, 11:30]
“We had no idea initially what the kidnap
was for. We were searching associates, we
looked for any previous criminal convictions,
we spoke to neighbours, and telephone
information for his phone. One of the neighbours
had suspected he had been kidnapped, and a
witness had seen him being bundled into a
car and alerted the police because they knew
he was vulnerable.”
      </p>
      <sec id="sec-8-1">
        <title>Extracted Questions: What people are associates of victim? Goals</title>
      </sec>
      <sec id="sec-8-2">
        <title>Understand</title>
        <p>the motive,
the risk to
the victim,
and possible
suspects</p>
      </sec>
      <sec id="sec-8-3">
        <title>Goals Find ciates asso</title>
        <p>Does the victim have any previous convic- Find
convictions? tions</p>
      </sec>
      <sec id="sec-8-4">
        <title>Victim name</title>
      </sec>
      <sec id="sec-8-5">
        <title>What calls have involved the victims phone? Find calls</title>
      </sec>
      <sec id="sec-8-6">
        <title>Cues</title>
      </sec>
      <sec id="sec-8-7">
        <title>Man gone</title>
        <p>missing.</p>
        <p>Thought he
had been
kidnapped
due to
witness report.
known
to be
vulnerable</p>
      </sec>
      <sec id="sec-8-8">
        <title>Cues Victim name</title>
      </sec>
      <sec id="sec-8-9">
        <title>Victim phone number</title>
      </sec>
      <sec id="sec-8-10">
        <title>Expectancies</title>
      </sec>
      <sec id="sec-8-11">
        <title>Actions</title>
        <p>Why?
a concise and clear representation of an analyst’s behaviour when
retrieving information, and thus can be used to give an explanation
structure for their intentions. We can design system processes that
mirror this representation.</p>
        <p>In Table 1, we also show how we extract individual questions
asked by analysts from interview statements and can structure them
against the RPD model. Furthermore, we can interpret the RPD
attributes more generically to suit multiple questions of the same
type. During the interviews each analyst provided many examples
of their information needs and the questions that they asked when
performing an investigation. For example, one analyst stated that
“I looked through every database for the victim’s name, custody
records, PNC (Police National Computer), stop and search, vehicles
he drove, to see if he had been stopped and searched with other
people in the vehicle and if they had been named.” [CTA: A1, 15:00].
From this statement, we can extract a number of questions posed
by the analyst that could be directed towards a CA, including “how
many vehicles have travelled to the victims address?” To answer
this question the analyst provides cues for ‘vehicles’, ‘travelled’ and
‘victims address’. Their goal is to retrieve summary information i.e.
‘how many’, and they are interested in finding a specific pattern of
data in the database, which connect the cues. Table 2 provides a
diferent example, with generic RPD attributes.</p>
        <p>In this paper, we present how RPD attributes can be used to
dynamically model analyst intentions for searching and retrieving
information, through Formal Concept Analysis (FCA). FCA is an</p>
      </sec>
      <sec id="sec-8-12">
        <title>Recognition- FCA Object: “Has [victim name] Primed Deci- been reported in any activity?” sion Aspect</title>
      </sec>
      <sec id="sec-8-13">
        <title>Cues</title>
      </sec>
      <sec id="sec-8-14">
        <title>Goals Expectancies</title>
      </sec>
      <sec id="sec-8-15">
        <title>Actions</title>
        <p>Why?</p>
      </sec>
      <sec id="sec-8-16">
        <title>What for?</title>
      </sec>
      <sec id="sec-8-17">
        <title>Pass specific input details (Vic</title>
        <p>tim Name, Activity)
Present confirmation
Expected that input details and
pattern exist
Perform adjacent information
search for entities extracted
Retrieve list for further
exploration.</p>
        <p>
          To find new lines of inquiry.
analysis approach which is efective at knowledge discovery and
provides intuitive visualisations of hidden meaning in data [
          <xref ref-type="bibr" rid="ref1">1</xref>
          ]. FCA
represents the subject domain through a formal context made of
objects and attributes of the subject domain [
          <xref ref-type="bibr" rid="ref14">14</xref>
          ]. By breaking down
analyst questions and structuring their components against the
RPD model we extract attributes which can be used by a CA to
process a response. In this study we identified specific RPD attributes
which address over 500 analyst questions, akin to those described
by analysts in interviews. We then performed FCA to identify
intention concepts. In our case, the subject domain comprises the
intentions of an analyst when they ask questions in an
investigation. Therefore, FCA objects are questions including “Has [victim
name] been reported in any activity?”. FCA attributes are the RPD
model specifics which the CA must recognise and act upon in
order to answer each question, such as the action ‘Perform adjacent
information search’. Attributes can be simple methods, for example
looking for single shortest paths or a pre-defined SPARQL pattern,
or they can be more advanced capabilities, such as clustering similar
instances. Importantly, each generic RPD attribute corresponds to
a functional process and therefore can be developed as a module.
FCA allows us to group modules together to form intentions, with
question objects that can be used to train text classification for the
user input to the CA.
        </p>
        <p>
          The lattice, as shown in Figure 1, presents distinct object
groupings. The final layer of concept circles are complete concept
intentions, where all parts of the RPD are considered. The circles are
sized based upon the number of associated questions. We can see
that three questions in our set can be answered by combining the
highlighted attributes. These attributes can answer the question,
‘how many vehicles are in our database?’, with ‘vehicle’ as a cue.
The CA looks for adjacent information i.e. where there are instances
of the class ‘vehicles’, presents a summary count, and retrieves a list.
To provide transparency we propose we can simply present what
attributes, and therefore functional processes, underpin a concept
with their descriptions. Our model-agnostic and modular approach
is akin to what Molnar [
          <xref ref-type="bibr" rid="ref11">11</xref>
          ] describes as the future of machine
learning interpretability. We have used the concept lattice to define
the intentions that an analyst can trigger through a CA interface,
where each intention reflects our explanation structure; the RPD
model.
4
4.1
        </p>
      </sec>
    </sec>
    <sec id="sec-9">
      <title>UNDERSTANDING CA RESPONSES</title>
    </sec>
    <sec id="sec-10">
      <title>Participants and Method</title>
      <p>We interviewed four intelligence analysts with more than 10 years
operational experience, from a diferent organisation to those
interviewed previously. We aimed to explore their requirements for
understanding the responses and processes of a CA in the context
of a criminal investigation. Each interview lasted an hour and we
presented interviewees with a series of questions and
corresponding CA responses with two explanation conditions, switching the
order of presentation. For one condition, responses described the
data alone (1) and, in the other condition, the data and system
processes (2). We were not attempting to test the diferences between
conditions, rather we used them as a starting point from which
we could explore additional needs. Throughout interviews a single
researcher took extensive notes from which individual statements
were extracted. In total there were 114 distinct statements extracted,
with counts for each analyst ranging from 24 to 34.
4.2</p>
    </sec>
    <sec id="sec-11">
      <title>Analysis and Results</title>
      <p>
        To analyse the statements we used an approach called Emergent
Themes Analysis (ETA), as described by Wong and Blandford [
        <xref ref-type="bibr" rid="ref19 ref20">19,
20</xref>
        ], where broad themes, which are similar ideas and concepts, are
identified, indexed and collated. ETA is useful for giving a feeling
of what the data is about, with structure, and is fast and practical
[
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]. A single researcher analysed the statements and identified
that they could be coded against the core functional components
of a CA, for example ‘System Processes’ as shown in Table 3. From
these components, we have drawn out the specific understanding
needed for CA responses as sub-themes. The sub-themes are further
categorised to form a general framework (Table 4) for explanation
needs from an intelligent CA system.
Exploring the interview data through the ETA method and
structure is helpful when we come to design CA components. For
example, examining Table 3 again, we can see that to provide
understanding of system processes to an analyst we need to allow for
clarification of both input variables and processes. Drawing upon
details in the statements we can see that it is important to clarify
any constraints related to the search inputs, the general capabilities
of the system as a whole, and specific processes applied in any
instance. We can incorporate explanations that provide clarification
of these aspects, in addition to solutions for other themes extracted
through ETA, into the design of our prototype application.
      </p>
      <p>
        An analyst’s ability to have clarification, verification and
justification of system processes is crucially important, as identified by
all analysts interviewed. This finding supports the framework for
providing algorithmic transparency presented by Hepenstal et. al
[
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] and reiterates the need to go beyond traditional approaches to
explainable AI (XAI) which focus upon explanations of the
important features for a model and accuracy measures. Specific concerns
included a need to justify follow up questions and the underlying
rationale of the system for use in court (ETA: A1; Q2; C1).
Additionally, an understanding of the system processes selected by the CA,
including descriptions of the methods applied (all analysts, multiple
statements), and inherent constraints, such as the questions which
cannot be answered by the CA and information which has been
omitted by the process (ETA: A2; Q1; C2 | A3; Q2; C2; | A4; Q4; C2).
Essentially, analysts need to be able to justify, clarify and verify the
CA intention triggered by their query and the related functional
attributes. We believe our RPD explanation structure provides a
neat mechanism to pick apart the system processes and provide,
for each, the understanding required.
      </p>
      <p>
        In Table 4, we display the framework areas and related
subthemes that emerged from ETA. Specific areas in the explanation
framework can be linked to existing models for sensemaking, such
as the Data Frame Model [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] for elaborating and reframing
questions, or Toulmin’s model for argumentation [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ] to provide
justification. Table 5 presents the key framework areas for each
component theme, where at least two analysts made associated statements,
together with a summary of sub-themes specific to both CA
component and framework area. Diferent CA components draw more
heavily on particular aspects of the framework and therefore our
ETA analysis helps us to design and tailor explanations for each
component.
5
      </p>
    </sec>
    <sec id="sec-12">
      <title>CA PROTOTYPE</title>
      <p>
        We have developed an initial prototype CA application called Pan,
which uses FCA to define the diferent intention concepts to which
it can respond. The objects (questions) which are attached to a
concept are used as training data for machine learning text
classification, so that a user’s question can be matched to an appropriate
intention. Each intention concept has associated attributes and
we have developed methods to handle these as individual models,
which create query syntax and interact with the database. In this
way, FCA can combine multiple distinct combinations of attribute
models flexibly to meet diferent analyst intentions. We propose
that by combining model-based attributes with FCA to define
intention concepts we provide a highly flexible approach to developing
CA intentions. The objects and corresponding RPD attributes are
critical for providing visibility to an analyst for the responses given
by a CA and are akin to explainability scenarios i.e. “narratives of
possible use that seek to answer the questions: who will use this
system and what might they need to know to be able to make sense
of its outputs?” [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ]
      </p>
      <p>Our work to identify the core understanding needs for CA
components has helped to inform the design of explanations for diferent
parts of the system, for example, when the CA matches user input
to an intention concept, triggers associated attribute models, and
responds. The explanation provides information required for an
analyst to understand the CA component themes of ‘Data’,
‘Extracted Entities’, and ‘Response’. As an analyst types their query
and entities are extracted, they are provided with identifier
information where possible. We have also designed for the ability for
an analyst to inspect and verify system goals and constraints. In
our prototype we allow the user to step into the intention concept
which has been triggered through a dialog window, so they can
inspect and verify clear textual descriptions with our explanation
structure, of the cues, goals, actions, expectancies and purpose of
the intention. For example, when a concept triggers the action for
ifnding single shortest path connections between instances, the
analyst is presented with a description that includes any constraints to
be wary of. Specifically, that it will not find longer paths or consider
multiple routes. These caveats will impact how the analyst
considers any information returned or how to rephrase their question.
The attribute descriptions for each RPD module hang together as a
narrative, akin to explainability scenarios. We intend to run
experiments with Pan and operational intelligence analysts to validate
our understanding of explanation needs and our RPD explanation
structure for CA intentions.
6</p>
    </sec>
    <sec id="sec-13">
      <title>USE CASES AND INITIAL FEEDBACK</title>
      <p>In order for AI systems to be used for high risk and high
consequence decision making they must provide transparency of their
reasoning. As put by one analyst, “[the principal analyst] said none
of my analysts would stand up in court where the beginning point
of their evidence is an algorithm.” [CTA: A4, 32:30] and that “You
have to be able to trace it (your reasoning) all the way back to
evidentially explain why you did each part... an analyst always has
to justify what they have done, so does a system.” [CTA: A4, 35:00]
We believe that Pan addresses these issues by providing
algorithmic transparency of its reasoning, using an architecture that aids
recognition and explanations that meet our explanation framework.
Early feedback from analysts on our approach is positive,
opening routes for Pan to be tested in high risk and high consequence
application domains where traditional CAs would not be deployed.
7</p>
    </sec>
    <sec id="sec-14">
      <title>CONCLUSIONS AND FUTURE WORK</title>
      <p>In this paper, we describe our approach to capture and model analyst
thought when retrieving information in a criminal investigation.
We also present analysis to understand their needs for explanations
from a complex CA system. Finally, we describe a prototype CA
which incorporates FCA and RPD to build intention concepts and is
therefore, we believe, transparent by design. We plan to evaluate the
transparency impacts of our approach to intention concept design,
gather additional requirements, and to validate our explanation
framework through experimentation with operational analysts. To
date we have not explored how a CA should present its responses
to an analyst. Thus, we will look to explore how explanations are
communicated, such as the specific textual or visual method.</p>
      <p>The role of investigation scope was prominent in CTA interviews
with analysts, where their questions were framed by the initial
scope, thus introducing the risk that important information beyond
the scope is missed. We will consider how CAs can help mitigate
the constraints of investigation scope, through machine reasoning
for example. Analysts expressed the desire to avoid obvious follow
up questions, so it would be helpful for a CA to predict and explore
additional questions autonomously. One approach for this is to
model investigation paths as a Bayesian network. Transparency is a
critical issue in autonomous systems and our explanation structure
could help understanding by aiding the explanations of system
behaviours across model states.</p>
    </sec>
    <sec id="sec-15">
      <title>ACKNOWLEDGMENTS</title>
      <p>This research was assisted by experienced military and police
analysts who work for the Defence Science Technology Laboratory
(Dstl) and the National Crime Agency (NCA) in the United
Kingdom.</p>
    </sec>
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