Expressiveness within Sequence Datalog

Motivated by old and new applications, we investigate Datalog as a language for sequence databases. We reconsider classical features of Datalog programs, such as negation, recursion, intermediate predicates, and relations of higher arities. We also consider new features that are useful for sequences, notably, equations between path expressions, and packing''. Our goal is to clarify the relative expressiveness of all these different features, in the context of sequences. Towards our goal, we establish a number of redundancy and primitivity results, showing that certain features can, or cannot, be expressed in terms of other features. These results paint a complete picture of the expressiveness relationships among all possible Sequence Datalog fragments that can be formed using the six features that we consider.

Path expressions, a central ingredient of query languages for object-oriented databases, are currently used as a purely navigational vehicle. We argue that this does not fully exploit their potential expressive power as a tool to specify connections between objects. In particular, a user should not be required to specify a path to be followed in full, but rather should provide enough information so that the system can infer missing details automatically. We present and study an extended mechanism for path expressions which resembles the omission of joins in universal relation interfaces. The semantics of our mechanism is given in the general framework of a calculus-like query language. Techniques from semantic query optimization are employed to obtain efficient specifications. We also consider the possibility that links can be traversed backwards, which subsumes previous proposals to specify inverse relationships at the schema level and also fully exploits the meaning of inheritance links.

that consist in grammars annotated with database programs. To query documents, we introduce an extension of OQL, the ODMG standard query language for object databases. Our extension (named OQL-doc) allows us to query documents without a precise knowledge of their structure using in particular generalized path expressions and pattern matching. This allows us to introduce in a declarative language (in the style of SQL or OQL), navigational and information retrieval styles of accessing data. Query processing in the context of documents and path expressions leads to challenging implementation issues. We extend an object algebra with new operators to deal with generalized path expressions. We then consider two essential complementary optimization techniques. We show that almost standard database optimization techniques can be used to answer queries without having to load the entire document into the database. We also consider the interaction of full-text indexes (e.g., inverted files) with standard database collection indexes (e.g., B-trees) that provide important speed-up.

Traditionally the database and programming language communities have taken different approaches to concurrency control. In programming languages, concurrency control is based upon the concept of the coordination of a set of cooperating processes by synchronisation. Language constructs such as semaphores [1], monitors [2], mutual exclusion [3], path expressions [4] and message passing [5] have been provided to support this concept. By contrast, in databases, concurrency is viewed as a system efficiency activity which allows parallel execution and parallel access to the data. However, each database process may have to suffer the indignity of abortion in order to sustain the illusion of non-interference. The key concept in databases is that of serialisability [6] which has led to the notion of atomic transactions [7] supported by locking or optimistic concurrency control methods [8].

We developed the Nested Relational Sequence Database System (NRSD System), which is built upon the Nested Relational Sequence Model (NRSM). The NRSM eliminates a substantial amount of redundancy embedded in XML documents and preserves the order of XML data. In this paper, we demonstrate that the storing and querying of XML data are desirable over an NRS relation, which we incorporate an index system into the NRSD System. We introduce a set of NRS operations which allow users to manipulate the XML data effectively and demonstrate how to use NRS operations to query the XML data stored in the NRSD System. Our experimental results confirm that the NRSD System substantially reduces the storage size of data. We also study the performance of the select and project operations having path expressions at different nested levels.

A Single Recursive Predicate Is Sufficient for Pure Datalog

BackgroundObesity is a multifaceted condition that impacts individuals across various age, racial, and socioeconomic demographics, hence rendering them susceptible to a range of health complications and an increased risk of premature mortality. The frequency of obesity among adolescent females in Iran has exhibited an increase from 6 to 9%, while among boys, it has risen from 2 to 7%. Due to the increasing prevalence and advancements in technology, the primary objective of this study was to develop and evaluate a smartphone-based app that would serve as an educational tool for parents about the matter of childhood overweight and obesity. Additionally, the app aimed to enhance parents’ capacity to effectively address and manage their children’s weight-related concerns.MethodsThe design of the present study is of an applied-developmental type. In the first phase, the content of related smartphone-based app was determined based on the needs identified in similar studies and the findings of a researcher-made questionnaire. The versions of the app were designed in the android studio 3 programming environment, using the Java 8 programming language and SQLite database. Then, in order to evaluate the app’s usability, ease of access, and different features, the standard usability evaluation questionnaire and the user satisfaction questionnaire (QUIS) were completed by the users.ResultsThe developed app has five main sections: the main page, recommendation section (with eight parts), charts over the time, child psychology, and reminders for each user. The designed app was given to 20 people including nutritionists and parents with children under 18 years of age for conducting usability evaluation. According to the scores of participants about the usability evaluation of the app, it can be concluded that groups participating in the study could use the program, and they rated the app at a “good” level. Overall performance of the app, screen capabilities, terms and information of the program, learnability, and general features are scored higher than 7.5 out of 9.ConclusionBy using this app, people can become familiar with the causes and symptoms of weight imbalance and manage their weight as best as possible. This app can be considered as a model for designing and creating similar broader systems and programs for the prevention, management, treatment and care of diseases, which aim to help control diseases as much as possible and increase the quality of life and reduce complications for be patients.

In this paper, we study the linguistic means that are acquired by two adult learners of a second language in order to express spatial concepts, and attempt to define the linguistic and communicational factors determining the observed acquisition. The data analysed come from the European Science Foundation’s second language data base (Feldweg 1993), and they allow us to adopt both a longitudinal and a cross-linguistic approach: we compare the acquisition of Dutch and French by Moroccan learners. The results obtained are briefly compared and contrasted with those of previous work in a similar framework, in particular Carroll/Becker (1993).

The logic programming language Datalog has been extensively researched as a query language for deductive databases. Although similar to Prolog, the Datalog operational mechanisms are more intricate, leading to computations quite hard to debug by traditional approaches. In this paper, we present a theoretical framework for debugging Datalog programs based on the ideas of declarative debugging. In our setting, a debugging session starts when the user detects an unexpected answer for some query, and ends with the debugger pointing to either an erroneous predicate or to a set of mutually recursive predicates as the cause of the unexpected answer. Instead of representing the computations by means of trees, as usual in declarative debugging, we propose graphs as a more convenient structure in the case of Datalog, proving formally the soundness and completeness of the debugging technique. We also present a debugging tool implemented in the publicly available deductive database system DES following this theoretical framework.

In this paper, we discuss some design principles that will aid in the design and querying of multimedia databases. We use an object-relational data model and argue that multimedia objects should normally have a special attribute called ‘core’ which stores the real object itself in contrast to the abstraction which is reflected in the rest of the attributes. We present an extension to the ER Diagram that takes advantage of the ‘core’ notion to facilitate design of multimedia databases. We discuss some desirable features in a query language for multimedia databases: simplifications like the use of path expressions and implicit use of functions (methods) as attributes, and explicit specification of the display layout and format either at the data definition level or query specification level. To materialize this last feature, we propose a display specification extension to SQL (SQL+D) that we have implemented.

We investigate logic-based query languages for sequence databases, that is, databases in which strings of symbols over a fixed alphabet can occur. We discuss different approaches to querying strings, including Prolog and Datalog with function symbols, and argue that all of them have important limitations. We then present the semantics of Sequence Datalog, a logic for querying sequence databases, and show how this language can be used to perform structural recursion over sequences.KeywordsActive DomainFunction SymbolQuery LanguagePredicate SymbolStructural RecursionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The characteristics of Soil Taxonomy are analyzed relative to various techniques for developing expert systems. Special emphasis is placed on computer program features that allow for more consistent application of classification systems and make them more user-friendly and understandable. We studied the functional logic and query processes employed by Soil Taxonomy to identify soil individuals and compared the methods with those used in other natural object classification systems. Numerical and classical identification methods and program features found in recent computer programs were evaluated for use with Soil Taxonomy. The keys in Soil Taxonomy are purely phenetic in nature and single-access in approach. In the absence of rule- and value confidence-weighting factors, the rules must be encoded without sequence modification to preserve the decision logic. Decisions in Soil Taxonomy query a large, often incomplete, and sometimes faulty data set, requiring error-checking of data and the addition of expert rules to the encoded decisions to prevent indecision. Soil Taxonomy rules check within the soil individual for the presence or absence of spatial and nonspatial differentiae, specific property values, or other qualifications. Soil Taxonomy is suitable as the subject of an object-oriented expert system, and planning has begun on development of an automated prototype for the Histosol, Andisol, Spodosol, and Oxisol soil orders. Expert system features coupled with additional models and algorithms can be used to improve the use and user-friendliness of Soil Taxonomy.

We consider spatial databases defined in terms of polynomial inequalities, and investigate the use of Datalog as a query language for such databases. Recursive programs are not guaranteed to terminate in this setting. Through a series of examples we show that useful restrictions on the databases under consideration or on the syntax of allowed programs, guaranteeing termination, are unlikely to exist. Hence, termination of particular recursive spatial queries must be established by ad-hoc arguments, if it can be established at all. As an illustration of the difficulties that can be encountered in this respect we discuss the topological connectivity query.

We consider two-dimensional spatial databases defined in terms of polynomial inequalities and focus on the potential of program- ming languages for such databases to express queries related to topo- logical connectivity. It is known that the topological connectivity test is not first-order expressible. One approach to obtain a language in which connectivity queries can be expressed would be to extend FO+Poly with a generalized (or Lindström) quantifier expressing that two points belong to the same connected component of a given database. For the expression of topological connectivity, extensions of first-order languages with recursion have been studied (in analogy with the classical relational model). Two such languages are spatial Datalog and FO+Poly+While. Although both languages allow the expression of non-terminating pro- grams, their (proven for FO+Poly+While and conjectured for spatial Datalog) computational completeness makes them interesting objects of study.Previously, spatial Datalog programs have been studied for more restric- tive forms of connectivity (e.g., piece-wise linear connectivity) and these programs were proved to correctly test connectivity on restricted classes of spatial databases (e.g., linear databases) only.In this paper, we present a spatial Datalog program that correctly tests topological connectivity of arbitrary compact (i.e., closed and bounded) spatial databases. In particular, it is guaranteed to terminate on this class of databases. This program is based on a first-order description of a known topological property of spatial databases, namely that locally they are conical.We also give a very natural implementation of topological connectivity in FO+Poly+While, that is based on a first-order implementation of the curve selection lemma, and that works correctly on arbitrary spatial databases inputs. Finally, we raise the question whether topological con- nectivity of arbitrary spatial databases can also be expressed in spatial Datalog.

This paper introduces a temporal relational algebra as a query language for temporal deductive databases, i. e., Temporal Datalog programs. In Temporal Datalog programs, temporal relationships among data are formalized through temporal operators, not by an explicit reference to time. The minimum model of a given Temporal Datalog program is regarded as the temporal database the program models intension ally. Users query temporal deductive databases using a temporal relational algebra (Tra), which is a point-wise extension of the relational algebra. During the evaluation of Tra expressions, portions of temporal relations are retrieved from a given temporal deductive database when needed. Bottom-up evaluation strategies such as the fixed point computation can be used to compute portions of temporal relations over intervals. An extension of Temporal Datalog with generic modules is also proposed. Through modules, temporal relations created during the evaluation of Tra expressions may be fed back to the deductive part for further manipulation.