OK, you stated:
a contract states that rollover protective devices " shall be installed on crawlers and rubber tire tractors such as dozers,push and pull tractors, winch tractors, mowers, off the highway self-propelled pneumatic tire earth movers, such as trucks, pans, scrapers, bottom dumps, and end dumps, motor graders." the contractor is palnning on using a certain type of trenching machine to perform the work. after the contract has been entered into,
a dispute arises as to whether the contractor must put the rollover protective device on the trencer. the contractor (naturally) says the contract does not require him to put the rollover protective device on the trencher, and the owner says the contract does require the rollover protective device. discuss as to this specific clause and what the rules in general are for such a situation.
The contract is silent or doesn't mention "trenchers".
Then the issue is - is a trencher of the type of machinery as contemplated by the parties that would be required to have a "roll-over" cage installed before it's use?
Depending upon if work was or wasn't performed on the job.
If no work done - then the contract could be voided because there wasn't a "meeting of the minds" in the matter.
If work was performed on the job - the parties could void the contract and the contractor be paid for the work performed to date on the job - restitution
for work performed.
If the contractor wanted to complete the contract and state the language of the contract didn't include the "trencher" and therefore he could complete the work. If the owner refused to allow such, the contractor could sue not only for the work performed but their expectation damages as to the profit from their completing the job.
If the owner refused the contractor to complete the job because of their thoughts about the "trencher" being defined within the contract - they could sue the contractor for breach of contract
and higher another contractor to complete the work and sue for the additional costs, if any.