{"id":338462,"date":"2016-12-19T12:35:59","date_gmt":"2016-12-19T20:35:59","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/?post_type=msr-research-item&#038;p=338462"},"modified":"2018-10-16T20:59:57","modified_gmt":"2018-10-17T03:59:57","slug":"assertional-correctness-proof-distributed-program","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/assertional-correctness-proof-distributed-program\/","title":{"rendered":"An Assertional Correctness Proof of a Distributed Program"},"content":{"rendered":"<p>I showed in <a href=\"https:\/\/www.microsoft.com\/en-us\/research\/publication\/time-clocks-ordering-events-distributed-system\/\">[27]<\/a> that there is no invariant way of defining the global state of a distributed system. Assertional methods, such as <a href=\"https:\/\/www.microsoft.com\/en-us\/research\/publication\/proving-correctness-multiprocess-programs\/\">[23]<\/a>, reason about the global state. So, I concluded that these methods were not appropriate for reasoning about distributed systems. When I wrote this paper, I was at SRI and partly funded by a government contract for which we had promised to write a correctness proof of a distributed algorithm. I tried to figure out how to write a formal proof without reasoning about the global state, but I couldn&#8217;t. The final report was due, so I decided that there was no alternative to writing an assertional proof. I knew there would be no problem writing such a proof, but I expected that, with its reliance on an arbitrary global state, the proof would be ugly. To my surprise, I discovered that the proof was quite elegant. Philosophical considerations told me that I shouldn&#8217;t reason about global states, but this experience indicated that such reasoning worked fine. I have always placed more reliance on experience than philosophy, so I have written assertional proofs of distributed systems ever since. (Others, more inclined to philosophy, have spent decades looking for special ways to reason about distributed systems.)<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I showed in [27] that there is no invariant way of defining the global state of a distributed system. Assertional methods, such as [23], reason about the global state. So, I concluded that these methods were not appropriate for reasoning about distributed systems. When I wrote this paper, I was at SRI and partly funded [&hellip;]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"_classifai_error":"","msr-author-ordering":[{"type":"user_nicename","value":"lamport","user_id":"32614"}],"msr_publishername":"","msr_publisher_other":"","msr_booktitle":"","msr_chapter":"","msr_edition":"","msr_editors":"","msr_how_published":"","msr_isbn":"","msr_issue":"","msr_journal":"Science of Computer 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