C. Small and A. Poulovassilis. An Overview of PFL. In Proceedings of the International Workshop on Database Programming Languages, pages 89--103. Morgan Kaufmann, 1991.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....query languages are based, becomes clear when side effecting qualifiers are taken into consideration. It is difficult to see how SQL based languages can be extended in a similar way to cope with side effects. List comprehensions are also included in a new functional database language called PFL [SP91] In P FDM [PG90] DAPLEX queries are translated to an abstract form of list comprehensions with which optimisation is carried out. The authors commented that list comprehensions allowed queries to be expressed declaratively while DAPLEX had a navigational style of querying. It is interesting ....

C. Small and A. Poulovassilis. An Overview of PFL. In Proceedings of the International Workshop on Database Programming Languages, pages 89--103. Morgan Kaufmann, 1991.

....be a comprehensive survey. My own work and related papers have influenced the choice of topics. The bibliography that follows is similarly affected. 2 A Bibliography As early as in [Sch78] and then more recently in e.g. AB87, HS89, ADG 89, SS89, ART90, ABD 90, MS91, AL 91, RS91, SP91, LMS 94] the design and implementation of collection types (sometimes called less ceremoniously bulk types) is identified as a key issue in database programming languages. The collection type constructs surveyed in this tutorial are related to forms of structural recursion (s.r. on ....

Carol Small and Alexandra Poulovassilis. An overview of PFL. In Proceedings of 3rd International Workshop on Database Programming Languages, Naphlion, Greece, pages 96--110. Morgan Kaufmann, August 1991.

....database update, view maintenance, integrity constraints, and active rules. The paradigm, however, does not have explicit state concepts. ffl Prevailing methods to identify persistent roots resort to name or string identifiers of them (Dearle et al. 1989; McNally and Davie 1991; McNally 1993; Small and Poulovassilis 1991). Regrettably, name identifiers would compromise the purity, and string identifiers would require dynamic type checking. As for the state based concepts, the functional programming community has proposed effective techniques, including continuation, linear typing (Wadler 1990) and ....

....specific implementation programming languages. Ceri and Fraternali (1997) cover various topics in the conceptual design phase with the object oriented or semantic database models and mapping abstract schemas to those in implementation models. FDL (Poulovassilis and Kind 1990) and its successor PFL (Small and Poulovassilis 1991; Small 1993) directly support the functional data model proposed by Shipman (1981) Active rule formalization The proposed manipulation of active rules is not based on a mathematical foundation or formal model. Instead, incorporating the functionality has been made possible through the ability ....

Small, C. and A. Poulovassilis (1991, August). An overview of PFL. In Proceedings of the Third International Workshop on Database Programming Languages, pp. 96--111. Morgan Kaufmann.

....code [15] Accident Blackspots Cooperating with a group at the London Centre for Transport studies we have constructed a parallel program to locate road traffic accident blackspots from police reports. This group already had an implementation [WH96] in the PFL database programming language [SP91]. However, our compiled sequential Haskell 0 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 12 14 16 No. Processors Blackspots, 40 Heterogeneous Tiles Ideal Relative Absolute Figure 2: Speedups on a Workstation Network 6 8 10 12 14 0 1 2 3 4 5 No. Processors Blackspots, Scaleup 75Kb Tiles User Time ....

Small C. and Poulovassilis A.P., "An Overview of PFL", Proc. 3rd. Intl. Workshop on Database Programming Languages, Kanellakis P. Schmidt J.W. (eds) (1991) Morgan Kaufman.

....of the system. The concept of monads as a method for implementing side effects in functional programming languages was discussed by Wadler [1] Moggi [23] and more recently in [7] A wide range of other theoretical concepts have also been developed (Linear Logic [5] Persistant Functional Language [29], Variable Type Logic of Effects [22] etc. Some of the proposed frameworks have been implemented in languages such as Haskell [17] Based on the work of Reynolds on idealized Algol [26] different type systems and derivation of the lambda calculus that include imperative statements have also ....

Carol Small and Alexandra Poulovassilis. An overview of PFL. In Proceedings of 3rd International Workshop on Database Programming Languages, Naphlion, Greece, pages 96--110. Morgan Kaufmann, August 1991.

....different dialects of comprehensions have found their way into various programming and query languages. For example, they have been applied to imperative languages such as Napier88 [27] Not surprisingly, comprehensions are popular among systems that adopt the functional data model, such as [30,33]. The algebra underlying comprehensions has been the starting point for the theoretical studies of query languages [7,17] Its role as an internal representation language for the ODMG 93 OQL [9] is investigated in [19] Object comprehensions differ from other dialects of comprehensions in that ....

C. Small and A. Poulovassilis. An Overview of PFL. In Proceedings of the International Workshop on Database Programming Languages, pages 89--103. Morgan Kaufmann, 1991.

....foundations for deductive languages, and we exploit some of this work in the context of our active system. PFL is a functional database programming language (DBPL) that is deductive in that it supports extensionally defined relations and functions that play the role of intentional relations [19, 26]. A key feature of functional languages is that expression evaluation is confluent: i.e. the value of an expression is independent of the order of evaluation of its sub expressions. In the case of PFL this is also true of expressions 2 which update the database since the type checker guarantees ....

Small, C. and Poulovassilis, A. "An overview of PFL", Proc. DBPL-3, Nauplion, 1991. pp 96-110.

.... exist which need to be resolved during the schema integration progress [Bat86] Turning now to the intentional part of a deductive database, rules are commonly expressed as formulae in a logic language such as Datalog [Ull88] However, following our recent work in functional database languages [Pou91, Sma91, Pou93], in this paper we assume that rules are expressed as equations in a functional language. Our reasons for pursuing a functional as opposed to a logic approach to deductive databases are discussed in greater detail in [Pou91, Pou93] and include: functional languages support higherorder functions ....

....we provide a brief description of the functional database programming language (DBPL) that we will be using to define the component and integrated databases, covering only the aspects of the language that are prerequisites for this paper. More comprehensive accounts can be found in previous papers [Sma91, Pou91, Pou93, Cou95]. 2.1 The type system Our functional DBPL is strongly, statically typed and we use the notation e 1 ; e n : t to indicate that the expressions e 1 ; e n all have type t. A number of primitive types are supported, such as Bool, Str, Num and Chr. Also supported are function ....

C. Small and A. Poulovassilis, "An Overview of PFL", in Proc. 3rd International Workshop on Database Programming Languages, Nafplion, August 1991.

....with a knowledge base (the intentional database) The extensional database is described by a database schema expressed using a particular data model. Rules are commonly expressed as formulae in a logic language such as Datalog [20] However, following recent work in functional database languages [7, 17, 8], we assume that rules are expressed as equations in a functional language. This language supports sets as first class objects and subsumes Datalog in the sense that any set of Datalog rules can be translated into a set of equations with the same semantics; in fact the language is more expressive ....

....of the paper is as follows. In Section 2 we give an overview of the functional database programming language (DBPL) that we use to define the component and integrated databases, covering only aspects of the language that are prerequisites for this paper; more comprehensive accounts can be found in [17, 7, 8, 11, 4]. In Section 3 we present our deductive database integration method. In Section 4 we compare our method with other related methods; for reasons of space this comparison is brief and a fuller discussion may be found in [21] Finally, in Section 5 we give our conclusions and indicate directions of ....

C. Small and A. Poulovassilis, "An Overview of PFL", in Proc. 3rd International Workshop on Database Programming Languages, Nafplion, August 1991.

....databases are thus largely complementary and recent research has aimed at integrating them [DOO] For reasons discussed at length in [PS91] we are interested in functional programming as opposed to logic programming as the basis for deductive databases. A database language, PFL [PS91] SP91] has been developed which exhibits all the desirable features of a functional language (such as higher order functions, static type checking and lazy evaluation) but which also supports functions that simulate the extensional and intentional relations of logic languages such as Datalog. In ....

....and directions of further work 2 Overview of PFL In this section we give an overview of the current PFL language, covering only aspects of the language that are prerequisites for our discussion of its new features in subsequent sections. More comprehensive accounts of PFL can be found in [PS91] SP91] 2.1 Types The syntax of PFL types is as follows, where oe ranges over type expressions, ff over type variables and n over n ary type constructors: oe : ff j oe 1 oe 2 j n oe 1 : oe n Types of the form oe 1 oe 2 are function types. Types of the form 0 are atomic types (so ....

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C. Small and A. Poulovassilis. An overview of PFL. In Proc. 3rd International Workshop on Database Programming Languages (DBPL-3), Nafplion, pages 96--110, 1991.

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Carol Small and Alexandra Poulovassilis. An overview of PFL. In Proceedings of 3rd International Workshop on Database Programming Languages, Naphlion, Greece, pages 96--110. Morgan Kaufmann, August 1991.

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