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1

A Non-Deterministic Multiset Query Language

Zieliński Bartosz

Fundamenta Informaticae

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2021

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Vol. 184, nr 2

141--180

EN

We develop a multiset query and update language executable in a term rewriting system. Its most remarkable feature, besides non-standard approach to quantification and introduction of fresh values, is non-determinism — a query result is not uniquely determined by the database. We argue that this feature is very useful, e.g., in modelling user choices during simulation or reachability analysis of a data-centric business process — the intended application of our work. Query evaluation is implemented by converting the query into a terminating term rewriting system and normalizing the initial term which encapsulates the current database. A normal form encapsulates a query result. We prove that our language can express any relational algebra query. Finally, we present a simple business process specification framework (and an example specification). Both syntax and semantics of our query language is implemented in Maude

2

Universal (and Existential) Nulls

Grahne Gösta, Moallemi Ali

Fundamenta Informaticae

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2019

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Vol. 167, nr 4

287--321

EN

Incomplete Information research is quite mature when it comes to so called existential nulls, where an existential null is a value stored in the database, representing an unknown object. For some reason universal nulls, that is, values representing all possible objects, have received almost no attention. We remedy the situation in this paper, by showing that a suitable finite representation mechanism, called Star Cylinders, handling universal nulls can be developed based on the Cylindric Set Algebra of Henkin, Monk and Tarski. We provide a finitary version of the cylindric set algebra, called Cylindric Star Algebra, and show that our star-cylinders are closed under this algebra. Moreover, we show that any First Order Relational Calculus query over databases containing universal nulls can be translated into an equivalent expression in our cylindric star-algebra, and vice versa. All cylindric star-algebra expressions can be evaluated in time polynomial in the size of the database. The representation mechanism is then extended to Naive Star Cylinders, which are star-cylinders allowing existential nulls in addition to universal nulls. For positive queries (with universal quantification), the well known naive evaluation technique can still be applied on the existential nulls, thereby allowing polynomial time evaluation of certain answers on databases containing both universal and existential nulls. If precise answers are required, certain answer evaluation with universal and existential nulls remains in coNP. Note that the problem is coNP-hard, already for positive existential queries and databases with only existential nulls. If inequalities ¬(xi ≈ x j) are allowed, reasoning over existential databases is known to be ∏2p -complete, and it remains in ∏ 2pwhen universal nulls and full first order queries are allowed.

3

Integration of queries to heterogeneous data sources using linq technology

Rusek M., Maguza J., Karwowski W.

Information Systems in Management

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2018

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Vol. 7, No. 3

180--189

EN

Nowadays, the data are available in a variety of formats such as relational database tables, xml files, rdf files or simply text files. Database systems have their own query languages and tools for the manipulation of data. On the other hand, most of today's applications are created in languages based on the object-oriented paradigm. From the level of the programming language it is important to use different sources of data in a uniform manner. The paper discusses the elements of the various query languages such as SQL XQuery or SPARQL. And then shows the capabilities of LINQ and its role in the creation of abstract data access layer. Then the possibilities of LINQ extension are discussed. As the example, design and implementation of LINQ provider for Allegro is presented.

4

Universal Query Language for Unified State Model

Wiśniewski P., Stencel K.

Fundamenta Informaticae

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2014

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Vol. 129, nr 1/2

177--192

EN

Unified State Model (USM) is a single data model that allows conveying objects of major programming languages and databases. USM exploits and emphasizes common properties of their data models. USM is equipped with mappings from these data models onto it. With USM at hand, we have faced the next natural research question whether numerous query languages for the data subsumed by USM can be clearly mapped onto a common language. We have designed and proposed such a language called the Unified Query Language (UQL). UQL is intended to be a minimalistic and elegant query language that allows expressing queries of languages of data models covered by USM. In this paper we define UQL and its concise set of operators. Next we conduct a mild introduction into UQL features by showing examples of SQL and ODMG OQL queries and their mapping onto UQL. We conclude by presenting the mapping of the theoretical foundations of these two major query languages onto UQL. They are the multiset relational algebra and the object query algebra. This is an important step towards the establishment of a fully-fledged common query language for USM and its subsumed data models.

5

Fuzzy querying with the use of interval-valued fuzzy sets

Myszkorowski K., Superson I.

Journal of Applied Computer Science

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2013

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Vol. 21, nr 1

89--105

EN

The paper deals with flexible queries in relational databases. Conditions included in queries are modeled with the use of interval-valued fuzzy sets. Each value returned by a query is associated with a subinterval of [0,1] which expresses a membership degree. The bounds of membership intervals have been determined for different operations of relational algebra and different SQL operators.

6

Języki zapytań strumieniowych baz danych

Guszpit W., Wilczek A.

Prace Naukowe Instytutu Informatyki Stosowanej Politechniki Wrocławskiej

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2007

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Nr 8

9-28

PL

Systemy Zarządzania Strumieniową Bazą Danych (SZSBD) stanowią alternatywę dla tradycyjnych relacyjnych bądź obiektowych Systemów Zarządzania Bazą Danych (SZBD). Tworzy się je na potrzeby aplikacji, w których nie może być użyty pasywny model przetwarzania, charakterystyczny dla tradycyjnych SZBD. System Zarządzania Strumieniową Bazą Danych stanowi aktywny element aplikacji, który na bieżąco generuje wyniki, wraz z napływem danych wejściowych. Możliwe jest to dzięki mechanizmowi rejestracji zapytań ciągłych (ang. continuous queries), które, w odróżnieniu od zapytań jednorazowych typowych dla tradycyjnych SZBD, wykonywane są w SZSBD stale przez określony przedział czasu. Taki sposób przetwarzania jest źródłem wymagań dla języka służącego do wyrażania zapytań ciągłych. W niniejszym artykule przedstawiono te wymagania oraz zaprezentowano wybrane, istniejące obecnie języki strumieniowe.

EN

Data Stream Management Systems (DSMS) are an alternative to traditional - relational or object oriented - Database Management Systems (DBMS). They are built for the purpose of the applications, in which passive processing model, characteristic for traditional DBMS, can not be applied due to constantly varying input parameters. Data Stream Management System is an active part of the application that outputs results in response to input parameters changes, represented by the incoming data sequences. This is possible since Data Stream Management Systems allow defining continuous queries to be performed for a period of time, contrary to one-time queries typical for traditional DBMS. This way of processing, for which data source come in form of sequences, defines set of features that language created for specifying continuous queries has to have. This document presents those features, and gives examples of query languages that own them.

7

Recursive Query Processing in SBQL

Pieciukiewicz T., Subieta K.

Prace Instytutu Podstaw Informatyki Polskiej Akademii Nauk

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2004

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Nr 979

1-56

EN

Recursive queries arę reąuired for many tasks of database applications. Among them we can mention Bill-Of-Material (BOM), various kinds of networks (transportation, telecommunication, etc.), processing semi-structured data (XML, RDF), and so on. The support for recursive queries in current query languages is limited and lacks of theoretical foundations. In particular, this concerns corresponding extensions of SQL in Oracle and DB2 systems. In this report we present recursive query processing capabilities for the object-oriented Stack-Based Query Language (SBQL) and compare them with similar capabilities in yariants of SQL. SBQL offers very powerful and flexible recursive querying capabilities due to the fact that recursive processing operators arę fully orthogonal to other features of this language. This report specifies corresponding SBQL constructs, such as transitive closures and fixed point equations. We compare them to other query languages, in particular to Datalog. We also present briefly optimization possibilities for recursive queries.

PL

Rekurencyjne zapytania są wymagane dla wielu zadań występujących w rzeczywistych aplikacjach baz danych. Wśród nich możemy wymienić rachunek materiałów (BOM), różne typy sieci (transportowa, telekomunikacyjna, itp.), przetwarzanie danych półstrukturalnych (XML, RDF) itd. Wspomaganie dla rekurencyjnych zapytań w obecnych językach zapytań jest ograniczone i pozbawione podstaw teoretycznych. W szczególności, dotyczy to odpowiednich rozszerzeń SQL w systemach Oracle i DB2. W raporcie przedstawiamy możliwości w zakresie rekurencyjnych zapytań w języku zorientowanym obiektowo Stack-Based Query Language (SBQL) i porównujemy je do podobnych możliwości w wariantach SQL. SBQL oferuje bardzo mocne i elastyczne możliwości w zakresie rekurencyjnych zapytań dzięki temu, że operatory służące do przetwarzania rekurencyjnego są całkowicie ortogonalne w stosunku do innych cech języka. Raport specyfikuje odpowiednie konstrukcje SBQL, takie jak tranzytywne domknięcia oraz równania stałopunktowe. Porównujemy je do innych języków zapytań, w szczególności do Datalogu. Na zakończenie prezentujemy krótko możliwości optymalizacji zapytań rekurencyjnych.

8

PathLog: a Query Language for Schemaless Databases of Partially Labeled Objects

Pankowski T.

Fundamenta Informaticae

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2002

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Vol. 49, nr 4

369-395

EN

In the paper we deal with the problem of modeling and querying information in schemaless databases of partially labeled objects (PLO-DB). Partially labeled objects are used for modeling data within repositories integrating both structured and semistructured data. The proposed PLO (Partially Labeled Objects) data model originates from the OEM data model and extends it by allowing partial labeling of objects. For PLO-DB we propose a rule-oriented query language PathLog, which data manipulation paradigm is based on set-theoretical operations and on rules (in Datalog style) involving Skolem functions and referential variables. The main contribution of the paper is the development of a formalized and consistent model of schemaless databases of partially labeled objects and its query language PathLog.

9

Meta-queries on deductive databases

Doherty P., Kachniarz J., Szałas A.

Fundamenta Informaticae

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1999

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Vol. 40, Nr 1

17-30

EN

We introduce the notion of a meta-query on relational databases and a technique which can be used to represent and solve a number of interesting problems from the area of knowledge representation using logic. The technique is based on the use of quantifier elimination and may also be used to query relational databases using a declarative query language called SHQL (Semi-Horn Query Language), introduced in [6]. SHQL is a fragment of classical first-order predicate logic and allows us to define a query without supplying its explicit definition. All SHQL queries to the database can be processed in polynomial time (both on the size of the input query and the size of the database). We demonstrate the use of the technique in problem solving by structuring logical puzzles from the Knights and Knaves domain as SHQL meta-queries on relational databases. We also provide additional examples demonstrating the flexibility of the technique. We conclude with a description of a newly developed software tool, The Logic Engineer, which aids in the description of algorithms using transformation and reduction techniques such as those applied in the meta-querying approach