There are times when you might have multiple rule developers who all to want to add conditions to the same rule but they don’t want to (or can’t) share access to the same rule document.
For example, you might have a rule which says "the advice to contact the customer helpline should be displayed if". On a large project you may have multiple rule developers all working on different topic areas but several topics advise the customer to contact the customer helpline. If you wanted to have all rule developers editing the one rule document, each rule developer would need to wait their turn to work on it.
Rule fragments allow each rule developer to have the rule proven in their own rule document to work on at their leisure. The rule fragments are combined into a single rule (separated by "or"s) when the rule documents are built. NOTE: Rule fragments only work in Word, not in Excel.
For more information on how to write rule fragments, see Prove an attribute using multiple rules.