Article
Объектные модели ODMG и SQL десять лет спустя: нет противоречий
In 2005, I wrote an article in which I discussed the most important features of the standards ODMG 3.0 (ODMG object model) and the SQL:2003 (SQL data model) and convincingly (as it seemed to me) argued that the similarity between the object model and object extensions to SQL is purely external, that close in mind syntactic constructions hide deep differences at the model level. Since then, it took many years for which I understood many things that were wrongly or insufficient correctly understood by me then, and gradually came to the conclusions that:
1. differences that seemed to me deep, are not such, and indeed are not differences at the model level;
2. the object extensions of SQL provide no less (and rather large) capabilities than the ODMG object model;
3. reasonably (from the standpoint of the database community) used DBMSes based on the ODMG data model, one will create databases and tools to manipulate them similar to those prescribed by the SQL data model.
When working with relational databases, the main time is loading, searching, update and unload data. When the amount of data is increased, the time to perform these operations is significantly increased, since in fact, all available records, and this reduces the performance and processing speed of the data. One possible way to increase productivity and increase speed data processing can be the use of indexes.
In this paper, we consider a solution that helps increase the speed of searching and retrieving data in relational DBMSs, such as Oracle and MySQL. This solution is called an index. We consider the types of indexes that are unique only for a particular DBMS, and indexes that are used in almost all databases. A test database for experiments has been created. The analysis is carried out for certain types of requests, the same for all investigated databases. Based on the results of the queries, a number of recommendations have been made on the use of indexes in specific DBMS and for specific types of query, as well as a number of general recommendations for writing relational queries
Many different data management systems are available nowadays, ranging from familiar SQL-based solutions to completely new systems designed from scratch. Wide range of available options made it possible to choose one that optimally suits application requirements. However, one can benefit even more from using different solutions within a single application for particular tasks. This paper focuses on collaboration between traditional SQL-based systems and currently popular NoSQL products.
At the moment, there are many tools that provide object approach to application development. This is the fact that the object-oriented paradigm is dominant in the development of new applications for any subject domains. Object-oriented approach is increasingly used in the implementation of database applications. The existence of their own strengths and weaknesses of each instrument, their main goal-to provide developers all the benefits of object-oriented paradigm for implementation of database applications. This paper provides a detailed overview of existing works and presents the unified testing model which is used to demonstrate different methods of presenting structural models in database applications. In last section the conclusions of the work and made suggestions for further development is given. This paper is the result of years of research and is based on numerous articles published in the Proceedings of the International Scientific and Practical Conference "Object Systems" (objectsystems.ru).
In this paper, we consider a solution that helps increase the search speed and data fetching in relational databases such as Oracle and MySQL. This solution is called an index. We consider types of indices, which are unique only for specific DBMS, and indexes, which are used in almost all databases. Created by test database for experiments. The analysis is carried out on certain types of queries that are the same for all investigated DBMS. Based results of the work of the requests, a number of recommendations on the use of indices in specific DBMS and for specific types of query, as well as a number of common recommendations for writing relational queries.
In this work we consider a solution that helps to increase the speed of search and retrieval of data in relational database management systems, such as ORACLE and MySQL.
This solution is called the index. We consider the types of indexes that are unique only for a particular database and indexes that are used in all DBMS.
The test database for experiments is created. The analysis is performed on certain types of queries, the same for all test databases. Based on the results of queries made a number of recommendations for using specific indexes in data-bases for specific types of request, as well as some general advice on writing relational queries
A model for organizing cargo transportation between two node stations connected by a railway line which contains a certain number of intermediate stations is considered. The movement of cargo is in one direction. Such a situation may occur, for example, if one of the node stations is located in a region which produce raw material for manufacturing industry located in another region, and there is another node station. The organization of freight traffic is performed by means of a number of technologies. These technologies determine the rules for taking on cargo at the initial node station, the rules of interaction between neighboring stations, as well as the rule of distribution of cargo to the final node stations. The process of cargo transportation is followed by the set rule of control. For such a model, one must determine possible modes of cargo transportation and describe their properties. This model is described by a finite-dimensional system of differential equations with nonlocal linear restrictions. The class of the solution satisfying nonlocal linear restrictions is extremely narrow. It results in the need for the “correct” extension of solutions of a system of differential equations to a class of quasi-solutions having the distinctive feature of gaps in a countable number of points. It was possible numerically using the Runge–Kutta method of the fourth order to build these quasi-solutions and determine their rate of growth. Let us note that in the technical plan the main complexity consisted in obtaining quasi-solutions satisfying the nonlocal linear restrictions. Furthermore, we investigated the dependence of quasi-solutions and, in particular, sizes of gaps (jumps) of solutions on a number of parameters of the model characterizing a rule of control, technologies for transportation of cargo and intensity of giving of cargo on a node station.
Event logs collected by modern information and technical systems usually contain enough data for automated process models discovery. A variety of algorithms was developed for process models discovery, conformance checking, log to model alignment, comparison of process models, etc., nevertheless a quick analysis of ad-hoc selected parts of a journal still have not get a full-fledged implementation. This paper describes an ROLAP-based method of multidimensional event logs storage for process mining. The result of the analysis of the journal is visualized as directed graph representing the union of all possible event sequences, ranked by their occurrence probability. Our implementation allows the analyst to discover process models for sublogs defined by ad-hoc selection of criteria and value of occurrence probability
The geographic information system (GIS) is based on the first and only Russian Imperial Census of 1897 and the First All-Union Census of the Soviet Union of 1926. The GIS features vector data (shapefiles) of allprovinces of the two states. For the 1897 census, there is information about linguistic, religious, and social estate groups. The part based on the 1926 census features nationality. Both shapefiles include information on gender, rural and urban population. The GIS allows for producing any necessary maps for individual studies of the period which require the administrative boundaries and demographic information.
Existing approaches suggest that IT strategy should be a reflection of business strategy. However, actually organisations do not often follow business strategy even if it is formally declared. In these conditions, IT strategy can be viewed not as a plan, but as an organisational shared view on the role of information systems. This approach generally reflects only a top-down perspective of IT strategy. So, it can be supplemented by a strategic behaviour pattern (i.e., more or less standard response to a changes that is formed as result of previous experience) to implement bottom-up approach. Two components that can help to establish effective reaction regarding new initiatives in IT are proposed here: model of IT-related decision making, and efficiency measurement metric to estimate maturity of business processes and appropriate IT. Usage of proposed tools is demonstrated in practical cases.