; (3) ensure the accuracy and security of the systems established under paragraphs (1) and (2); (4) enroll such individuals in the Rap Back Service; or (5) collect and analyze data to measure compliance with the level of enrollment of such individuals in the Rap Back Service. (d) Matching funds The portion of the costs of an activity provided by a grant under subsection (a) may not exceed 50 percent, unless the Attorney General waives, wholly or in part, the requirement under this subsection of a non-Federal contribution to the costs of an activity. (e) Authorization of appropriations There is authorized to be appropriated such sums as may be necessary to carry out this section. (f) Consistency with National Criminal History Improvement Program The Attorney General shall carry out the grant program under this section in a manner that is consistent with the National Criminal History Improvement Program. 4. Definitions In this Act: (1) The term firearm has the meaning given the term in section 921 of title 18, United States Code. (2) The term Rap Back Service means the capability of the Federal Bureau of Investigation’s Next Generation Identification system to provide notice to law enforcement agencies authorized by the Federal Bureau of Investigation to use such capability of arrests or other activity of licensees that might impact their continued eligibility for a license to purchase, possess, own, transfer, acquire, or carry a firearm in some or all circumstances or locations.