R. Hull, C. K. Yap, The format model: A theory of database organisation, Journal of the ACM 31, No. 3 (1984), 518--537.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....OtherwiseRNo r [L1, Ln] fl, fn] M Same as Otherwise. Assume r is Remy directory number corresponding to L1, Ln. More etficient than Otherwise. OtherwiseRaw [Li, Ln] fl, fn] M Same as Otherwise. However L1, Ln are label strings. 69 See also CO, CORecord. See [8] for a database perspective of variants. See [7] for a programming language perspective of variants. 70 17 CVT structure CVT Routines for conversion between sets, bags, and lists. Parallel, eager, and lazy versions are available. val ExtSB : val ExtBS : val ExtSL : val ExtLS : val ExtBL ....

Richard Hull and Chee K. Yap. The Format model: A theory of database organisation. Journal of the ACM, 31(3):518-537, July 1984.

....an extended E R model, similiar to the ERC model [19] is used. Unlike ERC which allows entity subtypes, multi valued and complex attributes, the extensions used here are limited to multi valued attributes and entitysubtyping. Complex attributes are omitted because studies of equivalence [8] have shown their removal (flattening) to be an equivalence preserving transformation. Mapping to such structures would, therefore, introduce unnecessary redundancy into the extraction process because during equivalence testing complex objects would be removed. Figure 2 illustrates the main ....

R. Hull and C. K. Yap. The format model: A theory of database organisation. Journal of the ACM, 3(31):518--537, 1984.

....of records type system of relational databases. It allows arbitrarily nested records, sets, lists, bags, and variants. A bag is also called a multi set, which is conceptually a set in which duplicates may occur. A list is conceptually a bag with order. A variant is also called a tagged union [9] and represents a type that is either this or that . Our sets, bags, and lists are homogeneous. In order to mix objects of di#erent types in a set, bag, or list, it is necessary to inject these objects into a variant type. We demonstrate this shortly when we build our TPR domain hunter. As an ....

Hull, R. and Yap, C.K., The Format model: A theory of database organisation, Journal of the ACM, 31(3):518--537, 1984.

....type l 1 : u 1 ; Delta Delta Delta ; l n : u n is called a variant object and is a pair l i : o such that o is an object of type u i ; that is, it is an object of type u i tagged with the label l i . Variants are also called tagged unions and co products. See Gunter [7] or Hull and Yap [9] for more information. Objects of type u v are functions from type u to type v. Included amongst the base types are num, string, bool, and unit (which is the type having exactly the empty record ( as its only object) It is also possible to extend CPL with new base types; see The Kleisli ....

Richard Hull and Chee K. Yap. The Format model: A theory of database organisation. Journal of the ACM, 31(3):518--537, July 1984.

....It allows arbitrarily nested records, sets, lists, bags, and variants. A bag is also called a multiset, which is conceptually a set in which duplicates may occur. A list is conceptually a bag with order. A variant is also called a tagged union and represents a type that is either this or that [13]. The sets, bags, and lists in the Kleisli Data Model are assumed to be homogeneous. So in order to mix objects of different types in a set, bag, or list, it is necessary to inject these objects into a variant type. However the Kleisli Data Exchange Format (described below) does not insist on ....

R. Hull and C. K. Yap. The Format model: A theory of database organisation. Journal of the ACM, 31(3):518--537, 1984.

....Labels (l s) must be distinct. l: t, l:t Variant types. Labels (l s) must be distinct. t Set types. N Named types. With the exception of variant, the other type constructors are common in most data models. A variant is also called a tagged union in the data model literature [12]. A data value is of variant type l 1 :t 1 ; l n :t n if it is formed by tagging a value of type t i with the label l i . For example, in Figure 1, a value of type Seqdesc is either a string that is a name (when tagged by name) a title (when tagged by title) a comment (when tagged by ....

R. Hull and C. K. Yap. The Format model: A theory of database organisation. Journal of the ACM, 31(3):518--537, July 1984.

....records type system of relational databases [8] It allows arbitrarily nested records, sets, lists, bags, and variants. A bag is also called a multi set, which is conceptually a set in which duplicates may occur. A list is conceptually a bag with order. A variant is also called a tagged union [11] and represents a type that is either this or that . As an example of a complex type, consider the following type that represents the feature table of a GenPept report from Entrez. a feature table provide information such as the location of zinc fingers in the protein sequence of that GenPept ....

R. Hull and C. K. Yap. The Format model: A theory of database organisation. Journal of the ACM, 31(3):518--537, July 1984.

....query languages. The general conservative extension result can be further improved in two ways. Firstly, Many modern data models possess an additional data structuring mechanism known variously as coproducts, variant types, sum types, or tagged unions (see Abiteboul and Hull [3] and Hull and Yap [12] for example) However, many papers on expressive power do not consider this feature [11, 7, 2] We extend the nested relational calculus of [6] with variant types and prove that the extended calculus remains conservative with respect to height of input output. Secondly, the proof we give for ....

....k =y] Then it is readily verified that whenever e ; e 0 , we have kek ke 0 k for any choice of . Therefore, the rewriting system is strongly normalizing. This completes the proof. 2 As remarked earlier in the report, variant mechanisms have been used in some data models such as [3] and [12]. However, many earlier interesting works on expressive power do not consider them [11, 7, 2] We hope the above result have rectified this situation to some extent. Our languages have been given semantics based on sets. These languages can be given semantics based on bags or on lists. For ....

R. Hull and C. K. Yap. The Format Model: A Theory of Database Organisation. Journal of the ACM, 31(3):518--537, July 1984.

....of records type system of relational databases. It allows arbitrarily nested records, sets, lists, bags, and variants. A bag is also called a multi set, which is conceptually a set in which duplicates may occur. A list is conceptually a bag with order. A variant is also called a tagged union [9] and represents a type that is either this or that . Our sets, bags, and lists are homogeneous. In order to mix objects of different types in a set, bag, or list, it is necessary to inject these objects into a variant type. We demonstrate this shortly when we build our TPR domain hunter. As an ....

R. Hull, C. K. Yap. The Format model: A theory of database organisation. Journal of the ACM, 31(3):518--537, 1984.

....of input output. The general conservative extension result can be further improved in two ways. Firstly, many modern data models possess an additional data structuring mechanism known variously as coproducts, variant types, sum types, or tagged unions; see Abiteboul and Hull [3] and Hull and Yap [14]. However, many papers on expressive power do not consider this feature [13, 10, 2] We extend the nested relational calculus of Breazu Tannen, Buneman, and Wong [7] with variant types and prove that the extended calculus remains conservative with respect to height of input output. Secondly, the ....

....ke 0 1 k Delta ke 0 3 k Delta ke 3 k . The latter is obviously less than the former. Therefore, the rewrite system is strongly normalizing. This completes the proof. 2 As remarked earlier, variant mechanisms have been used in some data models such as Abiteboul and Hull [3] and Hull and Yap [14]. However, many earlier interesting works on expressive power do not consider them [13, 10, 2] We hope the above result have rectified this situation to some extent. Our languages have been given semantics based on sets. These languages can be given semantics based on bags or on lists. For ....

R. Hull, C. K. Yap, The format model: A theory of database organisation, Journal of the ACM 31, No. 3 (1984), 518--537.

....of records type system of relational databases [8] It allows arbitrarily nested records, sets, lists, bags, and variants. A bag is also called a multi set, which is conceptually a set in which duplicates may occur. A list is conceptually a bag with order. A variant is also called a tagged union [11] and represents a type that is either this or that . Our sets, bags, and lists are homogeneous. In order to mix objects of different types in a set, bag, or list, it is necessary to inject these objects into a variant type. We will not be using variants here. As an example of a complex type, ....

....c.#p, 1) A then modify #a of c to 1 c.#a else if string substring (s, c.#p, 1) C then modify #c of c to 1 c.#c else if string substring (s, c.#p, 1) G then modify #g of c to 1 c.#g else modify #t of c to 1 c. #t c S ] #p: p, #a: 0, #c: 0, #g: 0, #t: 0) p [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 ]] nr in [ #position: p, #consensus: mk consensus (C) #a pc: a pc, #c pc: c pc, #g pc: g pc, #t pc: t pc) q hist, a pc = mk pc (q.#a) c pc = mk pc (q.#c) g pc = mk pc (q.#g) t pc = mk pc (q.#t) C = #l: a , #c: a pc) #l: c , #c: c pc) #l: g , #c: g pc) #l: ....

Richard Hull and Chee K. Yap. The Format model: A theory of database organisation. Journal of the ACM, 31(3):518--537, July 1984.

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R. Hull, C. K. Yap, The format model: A theory of database organisation, Journal of the ACM 31, No. 3 (1984), 518--537.

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