What it is
STANAG 4559 is a NATO Standardization Agreement, currently Edition 4, promulgated 28 March 2018. Like most STANAGs, it is not itself a technical specification. It is the agreement by which NATO nations commit to implement one or more of AEDP-17, AEDP-18 and AEDP-19, each Edition A, the publications that carry NATO's standard ISR (intelligence, surveillance and reconnaissance) library interfaces and services. The technical detail a reader wants sits inside whichever of those three publications a nation or contract specifies, not inside this short cover document. Read on its own, STANAG 4559 requires almost nothing of a contractor or integrator directly: its obligations run to nations, and it reaches a supplier only indirectly, once a nation has implemented it and a contract or tender brings AEDP-17, AEDP-18 or AEDP-19 into play.
Who it binds, and how
STANAG 4559 is explicit that it binds nations, not suppliers. Its letter of promulgation describes the enclosed agreement as one "which has been ratified by member nations, as reflected in the NATO Standardization Document Database (NSDD), is promulgated herewith." Ratification and implementation are separate steps, and once ratified, the agreement "is effective upon receipt and ready to be used by the implementing nations and NATO bodies." So "is STANAG 4559 mandatory" has no single answer: it depends on whether a given nation has ratified and implemented it, and, for a contractor, on whether a specific contract or tender then invokes AEDP-17, AEDP-18 or AEDP-19.
The interoperability requirement
The stated aim is "to respond to the following interoperability requirements," and the requirement itself is direct: "to promote interoperability of North Atlantic Treaty Organization (NATO) intelligence, surveillance, and reconnaissance (ISR) library interfaces and services for the exchange of shared ISR data, products and schemas." Under "Agreement," participating nations "agree to implement one or more of the following standards," listed as AEDP-17, Edition A, AEDP-18, Edition A, and AEDP-19, Edition A. A nation can choose any one of the three, or more than one; STANAG 4559 does not require all three at once, and it sets out no interface, format or schema of its own.
From ratification to reporting
Nations examine their own ratification of the STANAG and, where they have not already done so, advise the NATO Standardization Office (NSO) of their implementation intentions; they later provide their actual implementation details to the NSO as well. The STANAG counts itself implemented "when standard ISR library interfaces and services systems are incorporated into the nations' ... in accordance with the requirements of one or more of AEDP-17, AEDP-18 and AEDP-19, as documented in the national responses." Nations are invited to report their effective implementation using the form at Annex H to AAP-03(J); partner nations, invited to adopt the STANAG without the ratification obligation that binds a member nation, report their adoption using the form at Annex G to AAP-03(J).
Review and currency
This edition, Edition 4, supersedes the previous Edition 3 of STANAG 4559. "This STANAG is to be reviewed at least once every three years. The result of the review is recorded within the NSDD," and any nation or NATO body may propose a change at any time through a standardization proposal to the tasking authority, processed at the next review. It is supervised under NATO's Air Force Armaments Group (NAFAG, AC/224) and the Joint Capability Group on Intelligence, Surveillance and Reconnaissance (JCGISR); Germany is named as custodian.
What it does not cover
STANAG 4559 names no certification or accreditation scheme, no assessment body and no audit of a contractor or product. The only accountability it describes is procedural: nations reporting their own ratification and implementation decisions to the NSO, and the periodic review of the agreement's own currency described above.