Human 
Language 
Technology 
and 
communicative 
disabilities: 
Requirements 
and 
possibilities 
for 
the 
future 


12342

Marina 
B. 
Ruiter, 
Toni 
C.M. 
Rietveld, 
Catia 
Cucchiarini, 
Emiel 
J. 
Krahmer, 
Helmer 
Strik

1 
Sint 
Maartenskliniek 
Research, 
Development 
& 
Education, 
Nijmegen, 
Hengstdal 
3, 
6522 
JV, 
Nijmegen, 
The 


Netherlands, 
2 
Radboud 
University, 
Dept. 
of 
Linguistics, 
Erasmusplein 
1, 
6525 
HT 
Nijmegen, 
The 
Netherlands, 


3 
Nederlandse 
Taalunie, 
Lange 
Voorhout 
19, 
2501 
HN 
The 
Hague, 
The 
Netherlands, 
4 
Tilburg 
University, 
Dept. 
of 


Communication 
and 
Information 
Sciences, 
P.O. 
Box 
90153, 
5000 
LE 
Tilburg, 
The 
Netherlands. 


E-mail: 
m.ruiter@maartenskliniek.nl, 
a.rietveld@let.ru.nl, 
ccucchiarini@taalunie.org, 
e.j.krahmer@uvt.nl, 


w.strik@let.ru.nl 


Abstract 


For 
some 
years 
now, 
the 
Nederlandse 
Taalunie 
(Dutch 
Language 
Union) 
has 
been 
active 
in 
promoting 
the 
development 
of 
human 
language 
technology 
(HLT) 
applications 
for 
users 
of 
Dutch 
with 
communication 
disabilities. 
The 
reason 
is 
that 
HLT 
products 
and 
services 
may 
enable 
these 
users 
to 
improve 
their 
verbal 
autonomy 
and 
communication 
skills. 
We 
sought 
to 
identify 
a 
minimum 
common 
set 
of 
HLT 
resources 
that 
is 
required 
to 
develop 
tools 
for 
a 
wide 
range 
of 
communication 
disabilities. 
In 
order 
to 
reach 
this 
goal, 
we 
investigated 
the 
specific 
HLT 
needs 
of 
communicatively 
disabled 
people 
and 
related 
these 
needs 
to 
the 
underlying 
HLT 
software 
components. 
By 
analysing 
the 
availability 
and 
quality 
of 
these 
essential 
HLT 
resources, 
we 
were 
able 
to 
identify 
which 
of 
the 
crucial 
elements 
need 
further 
research 
and 
development 
to 
become 
usable 
for 
developing 
applications 
for 
communicatively 
disabled 
users 
of 
Dutch. 
The 
results 
obtained 
in 
the 
current 
survey 
can 
be 
used 
to 
inform 
policy 
institutions 
on 
how 
they 
can 
stimulate 
the 
development 
of 
HLT 
resources 
for 
this 
target 
group. 
In 
the 
current 
study 
results 
were 
obtained 
for 
Dutch, 
but 
a 
similar 
approach 
can 
also 
be 
used 
for 
other 
languages. 


1. 
Introduction 
Dutch 
language 
users 
with 
communication 
disabilities 
are 
hampered 
in 
their 
communicative 
efficacy 
and 
efficiency. 
That 
is, 
without 
other 
people 
helping 
them, 
they 
may 
not 
be 
able 
to 
get 
their 
message 
across 
adequately 
and 
fluently 
in 
Dutch. 
Similarly, 
it 
may 
be 
difficult 
for 
them 
to 
understand 
what 
other 
people 
tell 
them 
or 
put 
in 
writing. 
HLT 
may 
help 
to 
improve 
their 
functional 
communication 
skills, 
because 
HLT 
may 
allow 
them 
to 
restore 
or 
compensate 
their 
communication 
disorder. 
An 
example 
on 
aphasia 
may 
illustrate 
this. 
Aphasia 
is 
a 
neurological 
language 
disorder 
that 
can 
result 
from 
a 
stroke. 
The 
frequency 
of 
aphasics 
among 
stroke 
patients 
typically 
ranges 
from 
21 
to 
38% 
(e.g., 
Engelter 
et 
al., 
2006). 
Thus, 
at 
least 
21 
out 
of 
the 
100 
persons 
suffering 
a 
stroke 
develop 
aphasia 
in 
the 
sub-acute 
phase. 
Of 
these 
21 
persons, 
typically 
4 
pass 
away, 
4 
recover 
during 
the 
first 
months 
post-onset, 
and 
4 
remain 
aphasic. 
The 
outcome 
of 
the 
remaining 
9 
persons 
cannot 
be 
predicted 
accurately 
(Niewold, 
2006). 
Aphasia 
can 
manifest 
itself 
in 
all 
language 
faculties, 
such 
as 
spoken 
language 
production. 
There 
are 
strong 
indications 
that 
intensive 
training 
can 
improve 
aphasics’ 
functional 
communication 
skills 
(Bhogal, 
Teasell, 
Foley, 
& 
Speechley, 
2003). 
Emerging 
HLT 
technologies 
may 
for 
example 
be 
used 
to 
create 
virtual 
therapists 
that 
help 
aphasic 
speakers 
to 
train 
these 
skills 
(e.g., 
Cherney, 
Halper, 
Holland, 
& 
Cole, 
2008). 


Being 
far 
from 
exhaustive, 
we 
provide 
two 
other 
examples 
that 
illustrate 
how 
HLT 
enables 
communicatively 
disabled 
people 
to 
improve 
their 


communication 
skills. 
Within 
the 
Speech 
Algorithms 
for 
Clinical 
and 
Educational 
Applications 
(SPACE) 
project, 
speech 
recognition 
and 
synthesis 
technology 
were 
used 
to 
develop 
an 
automated 
reading 
tutor 
which 
allows 


(dyslectic) 
children 
to 
train 
their 
oral 
reading 
performance 
(e.g., 
Duchateau 
et 
al., 
2009). 
Technology 
that 
assesses 
the 
intelligibility 
of 
dysarthric 
speech 
was 
created 
as 
well 
(e.g., 
Van 
Nuffelen, 
Middag, 
De 
Bodt, 
& 
Martens, 
2009).1 


1.1. 
Human 
Language 
Technology 
and 
communication 
disabilities 
The 
Dutch 
Language 
Union 
is 
a 
Dutch-Flemish 


intergovernmental 
organisation 
that 
aims 
at 
creating 
the 
right 
conditions 
in 
which 
speakers 
of 
Dutch 
can 
use 
this 
language 
in 
as 
many 
communicative 
settings 
as 
possible. 
The 
leading 
principle 
of 
the 
efforts 
of 
the 
Dutch 
Language 
Union 
is 
to 
achieve 
this 
for 
all 
users 
of 
Dutch, 
also 
for 
those 
with 
communication 
disabilities. 
Against 
this 
background, 
the 
Dutch 
Language 
Union 
has 
been 
exploring 
the 
possibilities 
offered 
by 
HLT 
products 
and 
services 
to 
improve 
the 
verbal 
autonomy 
of 
communicatively 
disabled 
users 
of 
Dutch. 
A 
first 
initiative 
of 
the 
Dutch 
Language 
Union 
to 
investigate 
the 
potential 
of 
HLT 
for 
people 
with 
communication 
disabilities 
in 
the 
Netherlands 
and 
Flanders 
was 
the 
survey 
carried 
out 
by 
Rietveld 
and 
Stolte 
(2005). 
The 
authors 
interviewed 
experts 
from 
a 
variety 
of 
disciplines 
covering 
the 
various 
groups 
of 
people 
with 
communication 
disabilities 
and 
experts 
from 
the 
HLT 
sector 
(e.g., 
health 
care 
providers 
and 
providers 
of 
augmentative 
and 
alternative 
communication 
tools). 
With 
their 
responses, 
it 
was 
determined: 
(a) 
what 
HLT 
tools 
are 
currently 
available 
for 
people 
with 
communication 
disabilities, 
(b) 
what 
experiences 
the 
users 
have 
with 
these 
tools 
(in 
terms 
of 
quality 
and 
applicability), 
and 
(c) 
whether 
the 
HLT 
market 
could 
help 
to 
meet 
the 
needs 
that 
were 
not 
yet 
fulfilled. 
In 
2005, 
Rietveld 
and 
Stolte 


1 
For 
detailed 
information, 
see 
the 
SPACE 
home 
page: 
http://www.esat.kuleuven.be/psi/spraak/projects/SPACE/ 
. 



concluded 
that 
although 
people 
with 
communication 
disorders 
in 
the 
Netherlands 
and 
Flanders 
appeared 
to 
have 
urgent 
needs 
that 
could 
be 
fulfilled 
by 
HLT 
applications, 
these 
needs 
were 
not 
met 
at 
that 
time. 
Although 
several 
HLT 
applications 
have 
been 
developed 
over 
the 
last 
five 
years, 
anno 
2010, 
the 
HLT 
needs 
of 
communicatively 
disabled 
users 
of 
Dutch 
are 
not 
yet 
completely 
fulfilled. 
At 
least 
in 
part, 
this 
seems 
to 
be 
due 
to 
the 
diversity 
of 
the 
disorders 
underlying 
the 
communication 
disabilities, 
which 
makes 
it 
difficult 
to 
develop 
products 
that 
can 
be 
used 
by 
relatively 
large 
numbers 
of 
communicatively 
disabled 
people. 


1.2. 
A 
new initiative 
to 
investigate 
requirements 
and 
possibilities 
for 
the 
future 
The 
present 
study 
forms 
a 
continuation 
of 
the 
2005 
study 
conducted 
by 
Rietveld 
and 
Stolte. 
By 
investigating 
the 
specific 
needs 
of 
communicatively 
disabled 
people 
and 
relating 
these 
needs 
to 
the 
HLT 
software 
components 
underlying 
the 
applications 
called 
for, 
we 
sought 
to 
identify 
a 
minimum 
common 
set 
of 
HLT 
resources 
that 
is 
required 
to 
develop 
as 
many 
tools 
as 
possible 
for 
the 
wide 
range 
of 
communication 
disabilities. 
This 
research 
aim 
can 
be 
subdivided 
into 
several 
sub-questions: 


(a) 
Which 
HLT 
applications 
should 
be 
developed 
for 
users 
of 
Dutch 
with 
communication 
disabilities 
in 
order 
to 
meet 
their 
needs? 
(b) 
Which 
HLT 
software 
components 
underlie 
the 
applications 
that 
are 
most 
needed 
by 
users 
of 
Dutch 
with 
communication 
disabilities? 
(c) 
Are 
the 
essential 
HLT 
resources 
available, 
and 
– 
if 
so 
– 
does 
the 
quality 
suffice? 
(d) 
If 
the 
quality 
of 
an 
essential 
HLT 
resource 
does 
not 
suffice, 
what 
is 
the 
research 
effort 
necessary 
to 
improve 
its 
quality? 
2. 
Methods 
As 
discussed 
above, 
the 
diversity 
of 
the 
disorders 
underlying 
the 
communication 
disabilities 
and 
the 
various 
HLT 
needs 
make 
it 
difficult 
to 
develop 
products 
that 
can 
be 
used 
by 
large 
groups 
(Rietveld 
& 
Stolte, 
2005). 
In 
order 
to 
investigate 
whether 
these 
difficulties 
can 
be 
overcome, 
at 
least 
for 
the 
greater 
part, 
the 
present 
study 
followed 
an 
approach 
that 
was 
similar 
to 
the 
one 
adopted 
in 
preparation 
of 
the 
Dutch-Flemish 
HLT 
programme 
STEVIN 
(a 
Dutch 
acronym 
for 
Essential 
Speech 
and 
Language 
Technology 
Resources). 
This 
research 
and 
industry 
stimulation 
programme 
started 
in 
2004 
under 
the 
auspices 
of 
the 
Dutch 
Language 
Union 
and 
is 
funded 
by 
the 
Dutch 
and 
Flemish 
governments. 
An 
important 
element 
of 
the 
STEVIN 
programme 
was 
the 
definition 
of 
the 
Basic 
Language 
Resources 
Kit 
for 
Dutch 
(BLARK; 
Daelemans 
& 
Strik, 
2002). 
The 
BLARK 
concept 
(Krauwer, 
1998) 
was 
also 
used 
to 
specify 
a 
basic 
language 
resources 
kit 
for 
other 
languages, 
for 
example 
Arabic 
(e.g., 
Maegaard, 
Krauwer, 
& 
Choukri, 
2009) 
and 
Swedish 
(Elenius, 
Forsbom, 
& 
Megyesi, 
2006). 
In 
the 
BLARK, 
the 
basic 
software 
components 
that 
are 
essential 
for 
developing 
HLT 
applications 
were 
specified. 
By 


analysing 
the 
availability 
and 
quality 
of 
the 
various 
components, 
it 
could 
be 
determined 
which 
essential 
elements 
were 
missing 
or 
did 
not 
meet 
the 
requirements. 
As 
a 
consequence, 
it 
was 
possible 
to 
establish 
which 
HLT 
software 
components 
have 
to 
be 
developed 
with 
priority. 
Relevant 
for 
the 
present 
survey 
is 
that 
several 
matrices 
were 
used 
in 
defining 
the 
BLARK 
for 
Dutch: 
A 
distinction 
was 
made 
between 
applications, 
modules, 
and 
data. 
As 
will 
be 
discussed 
below, 
a 
similar 
approach 
was 
used 
in 
the 
present 
study. 


2.1. 
Matrices 
A 
stepping-stone 
to 
the 
present 
survey 
was 
a 
round 
table 
conference 
that 
was 
organised 
by 
the 
Dutch 
Language 
Union 
on 
September 
28, 
2007 
(Cucchiarini, 
2008). 
Experts 
from 
the 
HLT 
sector 
and 
from 
the 
clinical 
field 
participated. 
At 
this 
conference, 
a 
working 
group 
of 
experts 
was 
formed 
– 
the 
MATRIX 
working 
group 
– 
who 
discussed 
which 
matrices 
could 
be 
used 
in 
drawing 
up 
the 
HLT 
resources 
that 
are 
required 
to 
develop 
applications 
for 
communicatively 
disabled 
users 
of 
Dutch 
(Cucchiarini 
et 
al., 
2008; 
Strik, 
2008). 
During 
the 
survey, 
the 
matrices 
produced 
by 
the 
MATRIX 
working 
group 
were 
adapted 
as 
a 
result 
of 
feedback 
from 
the 
clinical 
field. 
The 
following 
matrices 
were 
used 
to 
specify 
the 
HLT 
needs 
as 
brought 
forward 
during 
the 
round 
table 
conference 
and 
in 
the 
interviews 
with 
20 
clinical 
experts: 


• 
Applications 
x 
conversions: 
What 
conversions 
between 
communication 
modalities 
are 
needed 
to 
develop 
an 
HLT-based 
tool? 
• 
Conversions 
x 
modules: 
What 
HLT 
software 
modules 
underlie 
each 
conversion? 
In 
the 
BLARK, 
the 
types 
of 
data 
needed 
to 
build, 
improve, 
or 
evaluate 
HLT 
software 
modules 
were 
defined 
as 
well. 
In 
the 
present 
study, 
however, 
we 
did 
not 
specify 
the 
data, 
because 
a 
separate 
database 
will 
be 
required 
for 
each 
(sub)group 
of 
communicatively 
disabled 
users 
of 
Dutch. 
This 
is 
related 
to 
the 
fact 
that 
the 
variability 
between 
these 
users 
is 
considerable. 
Even 
within 
a 
particular 
subgroup 
of 
communicatively 
disabled 
users 
of 
Dutch 
(e.g., 
within 
the 
group 
of 
dysarthric 
speakers) 
speech 
characteristics 
may 
vary 
to 
a 
great 
extent. 


2.1.1. 
Applications 
On 
the 
first 
axis 
of 
the 
matrices, 
we 
described 
the 
HLT 
applications 
that 
users 
of 
Dutch 
with 
communicative 
disabilities 
had 
indicated 
to 
be 
in 
need 
of. 
The 
following 
four 
dimensions 
were 
distinguished: 


• 
The 
purpose 
of 
the 
application: 
diagnosis, 
monitoring, 
restoration 
or 
compensation 
therapy, 
or 
augmentative 
and 
alternative 
communication 
(AAC). 
• 
The 
communication 
function 
which 
has 
to 
be 
fulfilled: 
reading, 
writing, 
listening, 
or 
speaking. 
• 
The 
target 
group, 
as 
defined 
by 
the 
underlying 
impairment: 
mental/cognitive 
(e.g., 
aphasia), 
sensory 
(e.g., 
blind), 
voice 
and 
speech 
(e.g., 

dysarthria), 
and 
motor 
(e.g., 
Repetitive 
Strain 
Injury). 


• 
Age: 
children 
and 
youngsters 
(up 
to 
18 
years), 
adults 
(18 
to 
65 
years), 
and 
elderly 
people 
(65 
years 
or 
older). 
HLT 
demands 
may 
differ 
depending 
on 
the 
age 
of 
the 
users. 
For 
instance, 
automatic 
speech 
recognition 
of 
children 
needs 
specific 
adjustment. 
2.1.2. 
Conversions 
In 
order 
to 
be 
able 
to 
specify 
for 
each 
and 
every 
application 
the 
underlying 
HLT 
software 
components, 
the 
applications 
were 
considered 
as 
conversions 
between 
the 
following 
five 
communication 
modalities: 


1) 
Spoken 
language 


2) 
Written 
language 


3) 
Non-verbal: 
images, 
animations, 
symbols, 


gestures, 
or 
agents 


4) 
Tactile: 
Braille 
or 
3D-images 
(with 
relief) 


5) 
Concepts: 
data, 
pictures, 
or 
key 
words, 
such 
as 


stock 
market 
reports 
printed 
in 
newspapers. 
To 
make 
clear 
what 
the 
relation 
is 
between 
conversions 
of 
modalities 
and 
(classes 
of) 
technologies, 
some 
examples 
are 
given 
below: 


1 
• 
2: 
speech 
recognition 


2 
• 
1: 
speech 
synthesis 


2 
• 
2: 
text 
modification, 
summarizing, 
indexing, 


etc. 


2 
• 
3: 
from 
text 
to 
virtual 
talking 
heads, 
agents, 


gestures, 
etc. 


2.1.3. 
Modules 
On 
the 
third 
axis 
of 
the 
matrices, 
we 
specified 
the 
HLT 
software 
modules 
underlying 
the 
conversions 
between 
communication 
modalities 
that 
communicatively 
disabled 
people 
need 
to 
use 
to 
get 
their 
messages 
across 
and/or 
to 
derive 
the 
communicative 
intention 
of 
other 
people. 
Since 
not 
all 
conversions 
could 
be 
realised 
with 
the 
BLARK 
modules 
(Daelemans 
& 
Strik, 
2002), 
the 
following 
additional 
modules 
were 
defined: 


• 
Text-to-gestures 
• 
Recognition 
of 
gestures 
• 
Text-to-symbols 
• 
Recognition 
of 
symbols 
• 
Generation 
of 
facial 
expression 
and 
articulation 
on 
talking 
heads 
• 
Recognition 
of 
pathological 
speech 
2.2. 
Procedure 
For 
each 
and 
every 
HLT 
need 
that 
was 
brought 
forward 
during 
the 
round 
table 
conference 
or 
in 
the 
interviews 
with 
the 
clinical 
experts, 
the 
underlying 
conversions 
were 
established 
(an 
example 
is 
given 
in 
Table 
1). 
As 
Table 
1 
illustrates, 
several 
conversions 
may 
be 
needed 
to 
develop 
a 
particular 
HLT 
application. 
In 
total, 
97 
conversions 
are 
needed 
to 
develop 
the 
65 
HLT 
applications 
that 
users 
of 
Dutch 
with 
communication 
disabilities 
seem 
to 
require. 


Requested 
HLT 
application: 
Writing 
Aid 
Description: 
People 
with 
mild 
aphasia 
or 
dysortho-
graphia 
could 
benefit 
from 
an 
application 
that 
they 
can 
use 
when 
writing 
a 
letter, 
paper, 
or 
e-mail. 
It 
should 
provide: 
word 
prediction, 
sentence 
prediction, 
spell 
and 
grammar 
checker 
tools, 
and 
advice 
on 
which 
register 
to 
use 
(e.g., 
formal 
or 
informal). 
It 
should 
also 
include 
speech 
synthesis, 
because 
it 
allows 
users 
to 
monitor 
and 
correct 
their 
own 
writing. 
Lastly, 
users 
should 
be 
able 
to 
produce 
a 
grammatically 
well-formed 
written 
sentence 
by 
putting 
symbols 
into 
a 
sequence. 
(1) 
Application 
-
-
-
-
Purpose: 
AAC 
Communication 
function: 
writing 
Target 
group: 
mental/ 
cognitive 
(aphasia, 
dysorthographia) 
Age: 
all 
(2) 
Conversions 
-
-
-
2 
• 
2 
2 
• 
1 
3 
• 
2 


Table 
1: 
Example 
of 
a 
requested 
HLT 
application 
(for 
explanation 
see 
text). 


2.2.1. 
Quantitative 
analysis 
of 
conversions 
The 
quantitative 
analysis 
of 
the 
97 
conversions 
derived 
with 
the 
procedure 
described 
above, 
yielded 
a 
hierarchy 
of 
conversions 
arranged 
by 
descending 
order 
of 
occurrence. 
In 
the 
current 
study, 
only 
the 
five 
most 
frequently 
occurring 
conversions 
were 
used 
for 
further 
analysis 
(cf., 
Table 
2). 
Table 
2 
for 
example 
shows 
that 
32% 
of 
the 
97 
conversions 
consisted 
of 
speech 
synthesis. 
One 
could 
argue 
that 
the 
conversions 
speech 
synthesis 
and 
speech 
recognition 
do 
not 
need 
to 
be 
developed 
for 
communicatively 
disabled 
users 
specifically 
as 
these 
conversions 
are 
already 
(at 
least 
partially) 
available 
for 
healthy 
users 
of 
Dutch. 
In 
arguing 
against 
this 
statement, 
it 
is 
important 
to 
emphasize 
that 
these 
conversions 
need 
specific 
adjustments 
in 
order 
to 
be 
employed 
in 
applications 
for 
communicatively 
disabled 
users. 
For 
example, 
due 
to 
the 
error-prone 
character 
of 
aphasic 
speech 
(e.g., 
substitutions 
of 
words, 
sounds, 
and 
ungrammatical 
utterances), 
the 
already 
available 
speech 
recognition 
resources 
do 
not 
suffice 
to 
recognise 
the 
speech 
of 
aphasic 
speakers. 


Conversion 
Frequency 
(in 
%) 
2 
• 
1 
Speech 
synthesis 
32 
1 
• 
2 
Speech 
recognition 
26 
2 
• 
2 
Text 
modification 
12 
3 
• 
1 
Non-verbal 
to 
speech 
8 
2 
• 
3 
Text 
to 
non-verbal 
7 


Table 
2: 
Hierarchy 
of 
the 
five 
most 
frequently 
occurring 
conversions 
(N 
= 
97). 



2.2.2. 
Achieving 
consensus 
The 
MATRIX 
working 
group 
achieved 
consensus 
on 
the 
software 
modules 
needed 
to 
realise 
the 
essential 
conversions. 
Secondly, 
the 
MATRIX 
working 
group 
agreed 
on 
the 
availability 
and 
quality 
of 
the 
software 
modules 
underlying 
the 
five 
most 
frequently 
occurring 
conversions. 
An 
HLT 
resource 
was 
considered 
available 
when 
it 
was 
either 
commercially 
or 
experimentally 
accessible 
(indicated 
with 
C 
and 
E 
respectively 
in 
Table 
3). 
Quality 
was 
rated 
at 
a 
4-point 
rating 
scale: 
good 
(G), 
sufficient 
(S), 
insufficient 
(I), 
or 
poor 
(P). 
In 
the 
present 
study, 
only 
the 
HLT 
software 
resources 
rated 
as 
sufficient 
or 
good 
were 
considered 
to 
be 
of 
adequate 
quality 
in 
order 
to 
be 
beneficial 
to 
communicatively 
disabled 
people. 
Lastly, 
the 
MATRIX 
working 
group 
made 
an 
estimation 
of 
the 
research 
effort 
needed 
to 
develop 
or 
improve 
HLT 
software 
modules 
whose 
quality 
appeared 
not 
to 
be 
up 
to 
the 
standards 
required. 
Only 
if 
a 
relatively 
small 
research 
effort 
was 
expected 
to 
be 
needed 
in 
order 
to 
improve 
quality 
or 
to 
make 
it 
more 
suitable 
for 
a 
specific 
application, 
was 
the 
complexity 
of 
a 
specific 
module 
rated 
as 
low 
(L). 
Conversely, 
whenever 
substantial 
research 
effort 
was 
anticipated 
to 
improve 
quality, 
the 
complexity 
was 
rated 
as 
high 
(H). 
The 
label 
average 
(A) 
was 
given 
if 
an 
average 
research 
effort 
was 
anticipated. 


3. 
Results 
In 
this 
section, 
we 
present 
the 
main 
results 
relating 
to 
the 
sub-questions 
formulated 
in 
the 
Introduction. 


3.1. 
HLT 
applications 
required 
Although 
inventorying 
the 
needs 
of 
people 
with 
communicative 
disabilities 
constituted 
the 
immediate 
goal 
of 
the 
present 
survey, 
it 
was 
not 
its 
ultimate 
goal. 
The 
ultimate 
goal 
of 
the 
current 
survey 
was 
to 
define 
the 
availability 
and 
quality 
of 
a 
minimum 
set 
of 
HLT 
resources 
that 
is 
required 
to 
develop 
as 
many 
tools 
as 
possible 
for 
the 
wide 
range 
of 
communication 
disabilities. 
For 
this 
reason, 
we 
do 
not 
provide 
a 
complete 
overview 
of 
the 
HLT 
applications 
required 
(N 
= 
65), 
but 
limit 
ourselves 
to 
providing 
some 
examples 
of 
useful 
applications 
in 
Section 
4.2 


3.2. 
Underlying 
HLT 
software 
components 
Table 
3 
presents 
the 
essential 
(indicated 
with 
X) 
and 
optional 
(indicated 
with 
parenthesis) 
modules 
underlying 
the 
five 
most 
frequently 
occurring 
conversions. 
For 
example, 
for 
the 
conversion 
speech 
synthesis, 
the 
following 
modules 
are 
essential: 
grapheme-to-phoneme 
conversion, 
text 
pre-processing, 
lemmatising 
& 
morphological 
analysis, 
morphosyntactic 
disambiguation, 
syntactic 
analysis, 
prosody 
generation, 
and 
complete 
speech 
synthesis. 
The 
module 
semantic 
& 
pragmatic 
analysis 
is 
optional. 


2 
Readers 
wishing 
to 
obtain 
the 
entire 
data 
set 
should 
contact 
the 
first 
author. 


3.3. 
Availability 
and 
quality 
of 
the 
modules 
As 
Table 
3 
illustrates, 
the 
availability 
and 
quality 
of 
the 
essential 
modules 
varies 
considerably. 
Some 
modules 
are 
both 
available 
and 
of 
sufficient 
quality. 
This 
holds 
for 
example 
for 
the 
HLT 
module 
lemmatising 
& 
morphological 
analysis. 
However, 
not 
all 
minimally 
required 
modules 
are 
available 
and 
good 
enough 
to 
be 
employed 
for 
developing 
applications 
for 
communicatively 
disabled 
users 
of 
Dutch. 
The 
module 
text 
generation 
is 
neither 
commercially 
nor 
experimentally 
available. 
Consequently, 
its 
quality 
is 
rated 
as 
poor. 
It 
seems 
paradoxical 
that, 
although 
language 
& 
dialect 
identification 
is 
not 
available, 
its 
quality 
is 
rated 
as 
sufficient. 
This 
is 
due 
to 
the 
fact 
that 
promising 
results 
have 
been 
obtained 
in 
scientific 
research; 
however, 
an 
experimental 
version 
of 
this 
module 
is 
not 
available 
yet. 


3.4. 
Research 
effort 
needed 
to 
improve 
quality 
For 
the 
HLT 
resources 
lacking 
sufficient 
quality, 
the 
anticipated 
research 
effort 
is 
given 
in 
Table 
3. 
For 
example, 
in 
order 
to 
improve 
the 
quality 
of 
the 
module 
recognition 
pathological 
speech 
a 
substantial 
research 
effort 
is 
needed. 
This 
is 
due 
to 
the 
considerable 
variability 
in 
speech 
production 
between 
and 
within 
communicatively 
disabled 
users 
of 
Dutch. 


4. 
Conclusions 
The 
most 
important 
question 
of 
the 
current 
survey 
is 
which 
HLT 
resources 
need 
to 
be 
developed 
or 
improved 
first 
in 
order 
to 
fulfil 
the 
needs 
of 
communicatively 
disabled 
users 
of 
Dutch 
best. 
As 
discussed 
in 
the 
Introduction, 
the 
criterion 
of 
multiple-usability 
was 
used 
in 
the 
present 
survey. 
Put 
differently, 
we 
sought 
to 
identify 
a 
minimum 
set 
of 
HLT 
resources 
that 
is 
required 
to 
develop 
as 
many 
tools 
as 
possible 
for 
the 
wide 
range 
of 
communication 
disabilities. 
It 
is 
however 
important 
to 
emphasize 
that 
other 
criteria 
can 
be 
used 
to 
answer 
the 
question 
presented 
above, 
such 
as 
prevalence 
and 
severity 
of 
the 
communication 
disorder. 
In 
addition, 
feasibility 
can 
be 
used 
as 
a 
criterion, 
as 
is 
illustrated 
by 
the 
survey 
of 
the 
Flemish 
Government 
department 
EWI 
(Dutch 
acronym 
for 
Economics, 
Science, 
and 
Innovation; 
Kenis, 
2009). 
In 
the 
present 
survey, 
however, 
we 
did 
not 
use 
feasibility 
as 
a 
criterion 
because 
the 
development 
and 
improvement 
of 
HLT 
resources 
is 
directly 
related 
to 
the 
amount 
of 
research 
budget 
available. 
For 
that 
reason, 
we 
will 
restrict 
ourselves 
to 
summarising 
the 
availability 
and 
quality 
of 
the 
essential 
HLT 
resources 
underlying 
the 
five 
most 
frequently 
occurring 
conversions. 
3 
In 
the 
following 
sections, 
we 
will 
summarise 
the 
research 
effort 
anticipated 
to 
improve 
the 
quality 
of 
the 
HLT 
resources 
as 
well. 


3 
For 
clarity’s 
sake, 
the 
availability 
and 
quality 
of 
the 
optional 
modules 
is 
not 
discussed 
in 
this 
section 
(for 
information 
about 
these 
modules, 
see 
Table 
3). 



Hierarchy 
5 
most 
frequently 
occurring 
conversions 
1 
(32%) 
1 
(26%) 
3 
(12%) 
4 
(8%) 
5 
(7%) 
Speech 
synthesis 
Speech 
recog-
nition 
Text 
modifi-
cation 
Non-
verbal 
to 
speech 
Text 
to 
non-
verbal 
Availa-
bility 
Quality 
Com-
plexity 
HLT 
software 
modules 
2 
• 
1 
1 
• 
2 
2 
• 
2 
3 
• 
1 
2 
• 
3 
C 
E 
BLARK 
for 
language 
technologyGrapheme-to-phoneme 
conversion 
X 
X 
X 
y 
y 
G 
n/a 
Text 
pre-processing 
X 
X 
X 
y 
y 
I 
L 
Lemmatising 
& 
morphological 
analysis 
X 
X 
X 
y 
y 
G 
n/a 
Morphosyntactic 
disambiguation 
X 
X 
X 
y 
y 
G 
n/a 
Syntactic 
analysis 
X 
X 
X 
X 
y 
y 
S 
n/a 
Semantic 
& 
pragmatic 
analysis 
( 
) 
X 
X 
X 
n 
n 
P 
H 
Text 
generation 
X 
X 
n 
n 
P 
A 
Language-pair 
dependent 
translation 
modules 
( 
) 
y 
y 
I 
H 
BLARK 
for 
Speech 
technology 
Prosody 
recognition 
( 
) 
n 
n 
P 
A 
Prosody 
generation 
X 
X 
X 
a 
y 
y 
S 
n/a 
Complete 
speech 
synthesis 
X 
X 
X 
b 
y 
y 
G 
n/a 
Complete 
speech 
recognition 
X 
y 
y 
I 
A 
Phone 
string 
computation 
( 
) 
y 
y 
G 
n/a 
Robust 
speech 
recognition 
X 
y 
y 
P 
H 
Speaker 
identification 
( 
) 
y 
y 
S 
n/a 
Language 
& 
dialect 
identification 
( 
) 
n 
n 
S 
n/a 
Adaptation 
X 
y 
n 
S 
n/a 
Confidence 
measures 
& 
utterance 
verification 
X 
y 
y 
I 
A 
Additional 
modules 
Text-to-gestures 
X 
n 
y 
I 
A 
Recognition 
of 
gestures 
X 
n 
y 
I 
H 
Text-to-symbols 
X 
y 
n 
I 
A 
Recognition 
of 
symbols 
X 
n 
n 
P 
L 
Generation 
of 
facial 
expression 
& 
articulation 
on 
talking 
heads 
X 
n 
y 
I 
L 
Recognition 
pathological 
speech 
X 
n 
n 
P 
H 


Table 
3: 
Essential 
(X) 
and 
optional 
( 
) 
HLT 
resources 
underlying 
the 
five 
most 
frequently 
occurring 
conversions, 
including 
availability 
of 
each 
software 
module 
(C 
= 
commercially, 
E 
= 
experimentally 
accessible), 
its 
quality 
(G 
= 
good, 
S 
= 
sufficient, 
I 
= 
insufficient, 
or 
P 
= 
poor), 
as 
well 
as 
its 
complexity 
(i.e., 
the 
research 
effort 
anticipated 
to 
develop 
or 
improve 
the 
HLT 
software 
module: 
L 
= 
low, 
A 
= 
average, 
or 
H 
= 
high). 
a,b 
Prosody 
generation 
and 
complete 
speech 
synthesis 
are 
necessary 
for 
converting 
text 
to 
NmG 
or 
SMOG 
(Dutch 
acronyms 
for 
spoken 
language 
supported 
by 
gestures). 


Table 
3). 
A 
relatively 
small 
research 
effort 
is 


4.1. 
Concluding 
remarks 
on 
speech 
synthesis 
anticipated 
to 
improve 
the 
quality 
of 
the 
latter 
module. 
Speech 
synthesis 
is 
the 
most 
frequently 
occurring 
Thus, 
by 
improving 
the 
quality 
of 
only 
one 
module, 
conversion 
underlying 
the 
tools 
needed 
by 
applications 
based 
on 
speech 
synthesis 
can 
be 
communicatively 
disabled 
users 
of 
Dutch. 
All 
seven 
developed. 
Table 
4 
gives 
an 
example 
of 
a 
speech 
essential 
modules 
are 
available 
and 
-except 
for 
text 
synthesis-based 
application 
that 
communicatively 
pre-processing 
-have 
sufficient 
or 
good 
quality 
(cf., 
disabled 
appear 
to 
find 
useful. 



Requested 
HLT 
application: 
Speech 
conversion 
Description: 
personalized 
synthetic 
speech 
is 
created 
on 
speaker’s 
own 
voice 
recordings 
at 
an 
early 
stage 
of 
their 
disease. 
(1) 
Application 
-
-
-
-
Purpose: 
AAC 
Communication 
function: 
speaking 
Target 
group: 
voice 
& 
speech 
(e.g., 
progressive 
diseases 
such 
as 
Amyotrophic 
Lateral 
Sclerosis 
or 
larynx 
extirpation) 
Age: 
adults 
and 
elderly 
(2) 
Conversion 
-1 
• 
1 


Table 
4: 
Example 
of 
a 
requested 
HLT 
application 
based 
on 
speech 
synthesis 


4.2. 
Concluding 
remarks 
on 
speech 
recognition 
Speech 
recognition 
is 
the 
second 
most 
frequently 
occurring 
conversion 
underlying 
the 
tools 
needed 
by 
communicatively 
disabled 
users 
of 
Dutch. 
As 
Table 
3 
illustrates, 
many 
HLT 
resources 
need 
to 
be 
developed 
or 
improved 
in 
order 
to 
enable 
communicatively 
disables 
users 
of 
Dutch 
to 
benefit 
from 
speech 
recognition. 
Four 
out 
of 
the 
five 
essential 
HLT 
modules 
are 
available. 
However, 
only 
one 
(i.e., 
adaptation) 
is 
of 
sufficient 
quality. 
The 
research 
effort 
needed 
to 
improve 
the 
quality 
of 
the 
remaining 
four 
modules 
ranges 
from 
average 
(complete 
speech 
recognition 
and 
confidence 
measures 
& 
utterance 
verification) 
to 
high 
(robust 
speech 
recognition 
and 
recognition 
pathological 
speech). 
As 
indicated 
before, 
a 
substantial 
research 
effort 
is 
needed 
in 
order 
to 
develop 
the 
module 
recognition 
pathological 
speech. 
This 
is 
due 
to 
the 
considerable 
between 
and 
within-subject 
variability 
in 
pathological 
speech 
production. 
An 
example 
of 
an 
HLT 
that 
is 
based 
on 
speech 
recognition 
is 
given 
in 
Table 
5. 


Requested 
HLT 
application: 
Conversation 
analysis 
Description: 
the 
conversation 
between 
communicatively 
disabled 
speaker 
and 
their 
conversation 
partners 
should 
be 
transcribed 
automatically. 
It 
should 
be 
possible 
to 
analyse 
the 
language 
(e.g., 
syntax, 
pragmatics) 
or 
speech 
characteristics 
(e.g., 
intonation, 
speech 
rate) 
of 
the 
speech 
sample 
as 
well. 
(1) 
Application 
-
-
-
-
Purpose: 
diagnosis, 
therapy 
Commun. 
function: 
speaking 
Target 
group: 
mental/cognition 
(e.g., 
aphasia), 
voice 
and 
speech 
(e.g., 
stuttering), 
motor 
(e.g., 
verbal 
apraxia) 
Age: 
all 
(2) 
Conversion 
-1 
• 
2 


4.3. 
Concluding 
remarks 
on 
text 
modification 
Four 
out 
of 
the 
six 
HLT 
modules 
necessary 
to 
execute 
text 
modification 
are 
available. 
Except 
for 
text 
pre-processing, 
all 
available 
modules 
are 
of 
sufficient 
or 
good 
quality. 
As 
indicated 
in 
Paragraph 
4.1., 
a 
small 
research 
effort 
is 
needed 
to 
improve 
text 
pre-processing. 
The 
modules 
semantic 
& 
pragmatic 
analysis 
and 
text 
generation 
are 
also 
essential 
for 
text 
modification; 
however, 
none 
of 
these 
two 
modules 
is 
available 
yet. 
The 
complexity 
of 
these 
modules 
is 
high 
and 
average 
respectively. 
An 
illustration 
of 
an 
application 
that 
– 
in 
part 
-is 
based 
on 
text 
modification 
is 
given 
in 
Table 
6. 


Requested 
HLT 
application: 
Summarising 
Description: 
the 
application 
should 
automatically 
summarise 
texts 
in 
spoken 
or 
written 
form. 
(1) 
Application 
-
-
-
-
Purpose: 
AAC 
Communication 
function: 
reading 
Target 
group: 
mental/cognition 
(e.g., 
dyslexia, 
aphasia, 
and 
mental 
retardation). 
Age: 
all 
(2) 
Conversions 
-
-
2 
• 
2 
1 
• 
2 


Table 
6: 
Example 
of 
a 
requested 
HLT 
application 
based 
on 
text 
modification 


4.4. 
Concluding 
remarks 
on 
non-verbal 
to 
speech 
Five 
out 
of 
the 
eight 
HLT 
modules 
essential 
to 
convert 
images, 
animations, 
symbols, 
gestures, 
or 
agents 
(i.e., 
non-verbal) 
into 
speech 
are 
available. 
Except 
for 
recognition 
of 
gestures, 
all 
available 
modules 
are 
of 
sufficient 
or 
good 
quality. 
A 
large 
research 
effort 
is 
needed 
to 
improve 
recognition 
of 
gestures. 
Semantic 
& 
pragmatic 
analysis, 
text 
generation, 
and 
symbol 
recognition 
are 
essential 
as 
well 
in 
this 
conversion; 
however, 
not 
accessible 
yet. 
The 
research 
efforts 
needed 
to 
improve 
these 
modules 
varies 
from 
low 
(symbol 
recognition), 
average 
(text 
generation), 
to 
high 
(semantic 
& 
pragmatic 
analysis). 
Table 
7 
illustrates 
an 
HLT 
application 
that 
is 
based 
on 
non-verbal 
to 
speech. 


Requested 
HLT 
application: 
Pictogram 
writing 
aid 
Description: 
the 
application 
should 
automatically 
generate 
a 
grammatically 
well-formed 
sentence 
based 
on 
the 
pictograms 
selected 
and 
sequenced. 
(1) 
Application 
-
-
-
-
Purpose: 
AAC 
Communication 
function: 
writing 
Target 
group: 
mental/cognition 
(e.g., 
dysorthographia, 
aphasia, 
and 
mental 
retardation). 
Age: 
all 
(2) 
Conversion 
-3 
• 
2 


Table 
5: 
Example 
of 
a 
requested 
HLT 
application 
based 
Table 
7: 
Example 
of 
a 
requested 
HLT 
application 
based 
on 
speech 
recognition 
on 
non-verbal 
to 
speech 



4.5. 
Concluding 
remarks 
on 
text 
to 
non-verbal 
Ten 
out 
of 
the 
eleven 
HLT 
modules 
that 
are 
necessary 
to 
convert 
text 
into 
images, 
animations, 
symbols, 
gestures, 
or 
agents 
(i.e., 
non-verbal) 
are 
available. 
However, 
only 
six 
out 
of 
these 
10 
modules 
are 
of 
sufficient 
quality. 
The 
research 
efforts 
needed 
to 
improve 
the 
quality 
of 
the 
modules 
that 
do 
not 
meet 
the 
requirements 
yet 
ranges 
from 
low 
(text 
pre-processing 
and 
generation 
of 
facial 
expression 
& 
articulation 
on 
talking 
heads), 
average 
(text-to-gestures 
and 
text-to-symbols), 
to 
high 
(semantic 
& 
pragmatic 
analysis) 
Table 
8 
illustrates 
an 
HLT 
application 
that 
– 
in 
part 
– 
is 
based 
on 
non-verbal 
to 
speech. 


Requested 
HLT 
application: 
Sign 
language 
translator 
Description: 
Deaf 
and 
hard 
of 
hearing 
always 
comprehend 
written 
language 
well 
enough 
to 
understand 
what 
others 
put 
in 
writing 
or 
tell 
them. 
For 
this 
reason, 
the 
application 
should 
convert 
spoken 
or 
written 
language 
into 
people 
do 
not 
automatically 
sign 
language. 
(1) 
Application 
-
-
-
-
Purpose: 
therapy, 
ACommunication 
funand 
listening 
Target 
group: 
sensoand 
hard 
of 
hearingAge: 
all 
AC 
ction: 
reading 
ry 
(e.g., 
deaf 
). 
(2) 
Conversions 
-
-
1 
• 
3 
2 
• 
3 


Table 
8: 
Example 
of 
a 
requested 
HLT 
application 
based 


on 
text 
to 
non-verbal 
4.6. 
Final 
remarks 
After 
drawing 
the 
preceding 
sections, 
conclusions 
preswe 
would 
like 
to 
ented 
make 
in 
the 
a 
final 


comment. 
The 
question 
which 
HLT 
resources 
need 
to 
be 
developed 
or 
improved 
first 
in 
order 
to 
fulfil 
the 
needs 
of 
communicatively 
disabled 
users 
of 
Dutch 
best, 
is 
an 
important 
one. 
However, 
we 
are 
well 
aware 
that 
the 
answer 
is 
more 
difficult 
than 
the 
question 
itself. 
In 
part 
this 
is 
due 
to 
the 
fact 
that 
several 
criteria 
can 
be 
used 
in 
providing 
an 
answer. 
Although 
multiple-
usability 
was 
used 
as 
a 
criterion 
in 
this 
study, 
we 
sought 
to 
present 
the 
results 
in 
such 
a 
way 
that 
other 
criteria 
could 
also 
be 
used 
in 
analysing 
the 
results 
obtained. 
Accordingly, 
these 
results 
can 
be 
used 
to 
inform 
policy 
institutions 
on 
how 
they 
can 
stimulate 
the 
development 
of 
HLT 
resources 
for 
the 
group 
of 
communicatively 
disabled 
users. 
In 
the 
current 
study 
results 
were 
obtained 
for 
Dutch, 
but 
a 
similar 
approach 
can 
also 
be 
used 
for 
other 
languages. 


5. 
Acknowledgements 
We 
are 
indebted 
to 
the 
(other) 
members 
of 
the 
MATRIX 
working 
group 
(Dirk 
Lembrechts, 
Hugo 
Van 
hamme, 
Lilian 
Beijer, 
and 
Vincent 
de 
Jong), 
all 
interviewees 
and 
participants 
of 
the 
round 
table 
conference 
of 
September 
28, 
2007 
(too 
many 
to 
name 


in 
person) 
as 
well 
as 
Antal 
van 
den 
Bosch, 
Onno 
Crasborn, 
Inge 
de 
Mφnnink, 
Bart 
Noλ, 
Arthur 
Dirksen, 
Michel 
Boekestein, 
Remco 
van 
Veenendaal, 
Loes 
Theunissen, 
and 
Marie 
Pruyn 
for 
their 
valuable 
contribution 
to 
the 
work 
presented 
in 
this 
paper. 


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