In this paper, we try to put to rest many of the objections to the universal relation concept that have appeared in the literature. First, we shall taxonomize the varieties of ideas that are sometimes called the "universal relation assumption." Then, we consider some of the arguments pro and con. In some cases, the arguments against were expressed prematurely, and solutions to the problems they expose have since been found. In other cases, the arguments against are simply fallacious. In still other cases, the problems pointed out are real, but simply serve to point out that the advantages of the universal relation are not gotten for free. We shall conclude the paper with a description of the algorithm used to interpret queries in System/U, and the reasoning behind it.
{"title":"The U. R. strikes back","authors":"J. Ullman","doi":"10.1145/588111.588114","DOIUrl":"https://doi.org/10.1145/588111.588114","url":null,"abstract":"In this paper, we try to put to rest many of the objections to the universal relation concept that have appeared in the literature. First, we shall taxonomize the varieties of ideas that are sometimes called the \"universal relation assumption.\" Then, we consider some of the arguments pro and con. In some cases, the arguments against were expressed prematurely, and solutions to the problems they expose have since been found. In other cases, the arguments against are simply fallacious. In still other cases, the problems pointed out are real, but simply serve to point out that the advantages of the universal relation are not gotten for free. We shall conclude the paper with a description of the algorithm used to interpret queries in System/U, and the reasoning behind it.","PeriodicalId":126896,"journal":{"name":"Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1982-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132671821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
‘l’hc IISMI IllOddS for distributed dak?basc~ [RSIJG] arc ba>ed on a set of “entities” distributed amuunL the nodes of a network. ‘l‘hcse entities arc xcwcd by USCI’S OF the database through “trcuxactions”, which are ccr& SCquCnccS of steps (“actions”) involviiig the jndiidllal entities. ‘L‘hC Steps arc grouped into trxwctions for twu disdnct purpuscs. i.jr,q a tramaction is t6cd as a unit of rccovcry: tither all of the steps of a transaction should bc carricci out, or none of them should; tl1llS, jf a transaction cannot bc complctcd. its initial steps must bc “undone” in some way. Second, a transaction is used to define atomicity: all of the !Xci)s of a transaction furm a logical atomic unit in the sense that it should appear to users of the database that all of thcsc steps are carried 014 consccutivcly, without any intcrvcning steps of other lransactions. This rcquircmcnt that transactions appear to be atomic is called “scriali/nbility” in the hlcralure [IGLT. RSI., IIG], and has been widely acccptcd as an important correctness criterion for distributed
{"title":"Multilevel atomicity","authors":"N. Lynch","doi":"10.1145/588111.588123","DOIUrl":"https://doi.org/10.1145/588111.588123","url":null,"abstract":"‘l’hc IISMI IllOddS for distributed dak?basc~ [RSIJG] arc ba>ed on a set of “entities” distributed amuunL the nodes of a network. ‘l‘hcse entities arc xcwcd by USCI’S OF the database through “trcuxactions”, which are ccr& SCquCnccS of steps (“actions”) involviiig the jndiidllal entities. ‘L‘hC Steps arc grouped into trxwctions for twu disdnct purpuscs. i.jr,q a tramaction is t6cd as a unit of rccovcry: tither all of the steps of a transaction should bc carricci out, or none of them should; tl1llS, jf a transaction cannot bc complctcd. its initial steps must bc “undone” in some way. Second, a transaction is used to define atomicity: all of the !Xci)s of a transaction furm a logical atomic unit in the sense that it should appear to users of the database that all of thcsc steps are carried 014 consccutivcly, without any intcrvcning steps of other lransactions. This rcquircmcnt that transactions appear to be atomic is called “scriali/nbility” in the hlcralure [IGLT. RSI., IIG], and has been widely acccptcd as an important correctness criterion for distributed","PeriodicalId":126896,"journal":{"name":"Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1982-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128890053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Many results in relational database theory on the structure of dependencies, query languages, and databases in general have now been established. However, neither (a) the reliance of these results on various assumptions, nor (b) the desirability or reasonableness of these assumptions themselves have been closely examined. These assumptions are nontrivial: examples include the universal relation assumption and the lossless join assumption.The purpose of the present paper is to clarify many of the existing assumptions, and point out weaknesses. This is desirable both to harden the statements of previous results, and to evaluate recent suggestions that certain assumptions (such as the acyclic JD assumption) may be useful for modeling "real world" databases. Specifically, studies are made of assumptions made for (1) universal relations, (2) functional dependency inference, and (3) decomposition theory. We show that:• Some assumptions (such as uniqueness of relationships among attributes) can be more powerful than they appear;• common treatment of FDs is sometimes inappropriate, and for example FD inferences such as {A → B, B → C} |= A → C can be incorrect;• the 'decomposition' approach to design may be hard to justify in real terms; and• Acyclic JDs may have drawbacks in eliminating ambiguity in queries and in modeling real enterprises.It is hoped that this exposition will help clarify some confusing issues in this field, and will lead to a better understanding of which assumptions are reasonable and useful in modeling the "real world".
{"title":"Assumptions in relational database theory","authors":"P. Atzeni, D. S. Parker","doi":"10.1145/588111.588113","DOIUrl":"https://doi.org/10.1145/588111.588113","url":null,"abstract":"Many results in relational database theory on the structure of dependencies, query languages, and databases in general have now been established. However, neither (a) the reliance of these results on various assumptions, nor (b) the desirability or reasonableness of these assumptions themselves have been closely examined. These assumptions are nontrivial: examples include the universal relation assumption and the lossless join assumption.The purpose of the present paper is to clarify many of the existing assumptions, and point out weaknesses. This is desirable both to harden the statements of previous results, and to evaluate recent suggestions that certain assumptions (such as the acyclic JD assumption) may be useful for modeling \"real world\" databases. Specifically, studies are made of assumptions made for (1) universal relations, (2) functional dependency inference, and (3) decomposition theory. We show that:• Some assumptions (such as uniqueness of relationships among attributes) can be more powerful than they appear;• common treatment of FDs is sometimes inappropriate, and for example FD inferences such as {A → B, B → C} |= A → C can be incorrect;• the 'decomposition' approach to design may be hard to justify in real terms; and• Acyclic JDs may have drawbacks in eliminating ambiguity in queries and in modeling real enterprises.It is hoped that this exposition will help clarify some confusing issues in this field, and will lead to a better understanding of which assumptions are reasonable and useful in modeling the \"real world\".","PeriodicalId":126896,"journal":{"name":"Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1982-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132846200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Session details: Session 1","authors":"Shin-Cheng Mu","doi":"10.1145/3248282","DOIUrl":"https://doi.org/10.1145/3248282","url":null,"abstract":"","PeriodicalId":126896,"journal":{"name":"Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1982-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114499588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Session details: Session 4","authors":"Ratul Mahajan","doi":"10.1145/3262683","DOIUrl":"https://doi.org/10.1145/3262683","url":null,"abstract":"","PeriodicalId":126896,"journal":{"name":"Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1982-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124900899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We consider the problem of optimizing conjunctive queries in the presence of inclusion and functional dependencies. We show that the problem of containment (and hence those of equivalence and non-minimality) is in NP when either (a) there are no functional dependencies or (b) the set of dependencies is what we call key-based. These results assume that infinite databases are allowed. If only finite databases are allowed, new containments may arise, as we illustrate by an example. We also prove a "compactness" theorem that shows that no such examples can exist for case (b).
{"title":"Testing containment of conjunctive queries under functional and inclusion dependencies","authors":"David S. Johnson, Anthony C. Klug","doi":"10.1145/588111.588138","DOIUrl":"https://doi.org/10.1145/588111.588138","url":null,"abstract":"We consider the problem of optimizing conjunctive queries in the presence of inclusion and functional dependencies. We show that the problem of containment (and hence those of equivalence and non-minimality) is in NP when either (a) there are no functional dependencies or (b) the set of dependencies is what we call key-based. These results assume that infinite databases are allowed. If only finite databases are allowed, new containments may arise, as we illustrate by an example. We also prove a \"compactness\" theorem that shows that no such examples can exist for case (b).","PeriodicalId":126896,"journal":{"name":"Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1982-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123330604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
(This paper did not arrive in time to be published in these proceedings).
(这篇论文没有及时到达，未能在这些会议上发表)。
{"title":"The relational model of data and cylindrical algebras","authors":"T. Imielinski, W. Lipski","doi":"10.1145/588111.588139","DOIUrl":"https://doi.org/10.1145/588111.588139","url":null,"abstract":"(This paper did not arrive in time to be published in these proceedings).","PeriodicalId":126896,"journal":{"name":"Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1982-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126976245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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