The DCR expression language has the following keywords reserved and can therefore not be used as activity ids.
abs
after
all
and
any
append
before
between
case
ceiling
count
concatenate
contains
context
date
day
decimal
define
distinct
duration
else
ends
entries
even
every
exp
extract
false
flatten
floor
for
get
if
in
index
insert
instance
item
length
log
lower
matches
max
mean
median
min
mode
modulo
month
now
null
number
odd
of
or
product
put
remove
replace
return
reverse
satisfies
some
sort
split
sqrt
starts
stddev
string
sublist
substring
sum
then
time
today
true
union
upper
value
values
week
year