Liberate: are only hidden power arcs needed when defining power arcs during STD cell characterisation?

Hi all,

I used command "read_library" and "write_template" to generate a tcl file for a BUFT cell (buffer with enable signal) based on an UMC technology. Among all the power arcs, there seems only "-type hidden" arcs which will not trigger any change on output node. I don't know why there is no "-type power" arc. Could anyone tell me if it is necessary or not to define a arc that will trigger an output change? ( I prefer necessary but I am not sure)

I also paste all generated power arcs as follows:

# power arcs from => I hidden
define_arc \
-type hidden \
-when "!OE&Z" \
-vector {Rxx} \
-pin I \
BUFT

# power arcs from => I hidden
define_arc \
-type hidden \
-when "!OE&Z" \
-vector {Fxx} \
-pin I \
BUFT

define_arc \
-type hidden \
-when "!OE&!Z" \
-vector {Rxx} \
-pin I \
BUFT

define_arc \
-type hidden \
-when "!OE&!Z" \
-vector {Fxx} \
-pin I \
BUFT

# power arcs from => OE hidden
define_arc \
-type hidden \
-when "I&Z" \
-vector {xRx} \
-pin OE \
BUFT

# power arcs from => OE hidden
define_arc \
-type hidden \
-when "I&Z" \
-vector {xFx} \
-pin OE \
BUFT

define_arc \
-type hidden \
-when "!I&!Z" \
-vector {xRx} \
-pin OE \
BUFT

define_arc \
-type hidden \
-when "!I&!Z" \
-vector {xFx} \
-pin OE \
BUFT

Any hint from experienced liberate user will be appreciated.

Regards,

Jiacong