Documenting SMV Assignments for COMP
- The SMV files that I provide for doing exercises may contain
bugs which have been placed there deliberately. Please do not
post to the newsgroup asking whether there is a bug in a
file. If you spot a bug in a file, try to locate the property
that would have caught the error (see the second part of "what to turn
in" below). Do not simply correct the file, as the ability to find
and interpret errors is one of the skills I want you to develop in
- Document your properties with an English description (not a
direct CTL translation -- for example, if the property is "AG (p -> AF
q)", I want descriptions like "whenever p is true, q is eventually
true", not "for all states on all paths, if p is true then on all
paths there is a future state in which q is true"). Put these
descriptions in as comments in the SMV file, with each description
located just before the corresponding SPEC. If you have a group of
related properties (for example, if you need to verify that the same
general property holds of each of three pairs of variables), you can
write one English comment for the entire group.
Analyzing Error Tracks
Analyzing an error track consists of three steps:
- Summarize the information you got out of the error track (ie,
describe the sequence of events that lead to the error). Your goal
here should be to summarize only the information that is relevant to the
error; SMV will give you a trace of all variables, not all of which
actually matter for the property you are verifying.
- Try to explain the cause of the error (ie, the property failed to
consider the case where X happens, I had misunderstood that the system
could do Y, a typo was made when entering the formula, etc).
- Describe briefly what you need to do to fix the error (ie, I need
to add condition X to the property, I need to add a FAIRNESS
What to turn in for each SMV problem
- A printout of the final version of the SMV file for the problem.
- If you found errors in the state machine definitions, provide
an error track analysis for any one error track that lead you to
finding such a bug in the design. Describe the change you had to
make. If I had provided you with the original SMV file, describe to
me where you made changes to the original file.
- Error track analysis for one property that failed because the
property was incorrectly stated. Pick a property that did not verify
on the first try (presumably you won't get them all right on the first
try, though if by chance you did, say so explicitly). Write up
analyses of two iterations of debugging this property (ie, write up
the first error track, change the property according to the error,
then write up the next error track you get for that same property).
If you had only one iteration of errors on all properties, just write
up that one iteration for any one property. If you had more than two
iterations of errors, you don't have to submit anaylses for the