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Extract, Transform, Load
Extract, transform, load (ETL) is a three-phase computing process where data is ''extracted'' from an input source, ''transformed'' (including cleaning), and ''loaded'' into an output data container. The data can be collected from one or more sources and it can also be output to one or more destinations. ETL processing is typically executed using software applications but it can also be done manually by system operators. ETL software typically automates the entire process and can be run manually or on recurring schedules either as single jobs or aggregated into a batch of jobs. A properly designed ETL system extracts data from source systems and enforces data type and data validity standards and ensures it conforms structurally to the requirements of the output. Some ETL systems can also deliver data in a presentation-ready format so that application developers can build applications and end users can make decisions. The ETL process is often used in data warehousing. ETL sys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JSON
JSON (JavaScript Object Notation, pronounced or ) is an open standard file format and electronic data interchange, data interchange format that uses Human-readable medium and data, human-readable text to store and transmit data objects consisting of name–value pairs and array data type, arrays (or other serialization, serializable values). It is a commonly used data format with diverse uses in electronic data interchange, including that of web applications with server (computing), servers. JSON is a Language-independent specification, language-independent data format. It was derived from JavaScript, but many modern programming languages include code to generate and parse JSON-format data. JSON filenames use the extension .json. Douglas Crockford originally specified the JSON format in the early 2000s. Transcript: He and Chip Morningstar sent the first JSON message in April 2001. Naming and pronunciation The 2017 international standard (ECMA-404 and ISO/IEC 21778:2017) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transpose
In linear algebra, the transpose of a Matrix (mathematics), matrix is an operator which flips a matrix over its diagonal; that is, it switches the row and column indices of the matrix by producing another matrix, often denoted by (among other notations). The transpose of a matrix was introduced in 1858 by the British mathematician Arthur Cayley. Transpose of a matrix Definition The transpose of a matrix , denoted by , , , A^, , , or , may be constructed by any one of the following methods: #Reflection (mathematics), Reflect over its main diagonal (which runs from top-left to bottom-right) to obtain #Write the rows of as the columns of #Write the columns of as the rows of Formally, the -th row, -th column element of is the -th row, -th column element of : :\left[\mathbf^\operatorname\right]_ = \left[\mathbf\right]_. If is an matrix, then is an matrix. In the case of square matrices, may also denote the th power of the matrix . For avoiding a possibl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surrogate Key
A surrogate key (or synthetic key, pseudokey, entity identifier, factless key, or technical key) in a database is a unique identifier for either an ''entity'' in the modeled world or an ''object'' in the database. The surrogate key is ''not'' derived from application data, unlike a ''natural'' (or ''business'') key. Definition There are at least two definitions of a surrogate: ; Surrogate (1) – Hall, Owlett and Todd (1976): A surrogate represents an ''entity'' in the outside world. The surrogate is internally generated by the system but is nevertheless visible to the user or application. ; Surrogate (2) – Wieringa and De Jonge (1991): A surrogate represents an ''object'' in the database itself. The surrogate is internally generated by the system and is invisible to the user or application. The ''Surrogate (1)'' definition relates to a data model rather than a storage model and is used throughout this article. See Date (1998). An important distinction between a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Record Linkage
Record linkage (also known as data matching, data linkage, entity resolution, and many other terms) is the task of finding records in a data set that refer to the same entity across different data sources (e.g., data files, books, websites, and databases). Record linkage is necessary when joining different data sets based on entities that may or may not share a common identifier (e.g., database key, URI, National identification number), which may be due to differences in record shape, storage location, or curator style or preference. A data set that has undergone RL-oriented reconciliation may be referred to as being ''cross-linked''. Naming conventions "Record linkage" is the term used by statisticians, epidemiologists, and historians, among others, to describe the process of joining records from one data source with another that describe the same entity. However, many other terms are used for this process. Unfortunately, this profusion of terminology has led to few cross- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Join (relational Algebra)
In relational algebra, a join is a binary operation, written as R \bowtie S where R and S represent relations, that combines their data where they have a common attribute. Natural join Natural join (⨝) is a binary operator that is written as (''R'' ⨝ ''S'') where ''R'' and ''S'' are relations. The result of the natural join is the set of all combinations of tuples in ''R'' and ''S'' that are equal on their common attribute names. For an example consider the tables ''Employee'' and ''Dept'' and their natural join: Note that neither the employee named Mary nor the Production department appear in the result. Mary does not appear in the result because Mary's Department, "Human Resources", is not listed in the Dept relation and the Production department does not appear in the result because there are no tuples in the Employee relation that have "Production" as their DeptName attribute. This can also be used to define composition of relations. For example, the composi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null (SQL)
In SQL, null or NULL is a special marker used to indicate that a data value does not exist in the database. Introduced by the creator of the Relational model, relational database model, E. F. Codd, SQL null serves to fulfill the requirement that all ''true relational database management systems (Relational database#RDBMS, RDBMS)'' support a representation of "missing information and inapplicable information". Codd also introduced the use of the lowercase Greek omega (ω) symbol to represent null in database theory. In SQL, NULL is a List of SQL reserved words, reserved word used to identify this marker. A null should not be confused with a value of 0. A null indicates a lack of a value, which is not the same as a zero value. For example, consider the question "How many books does Adam own?" The answer may be "zero" (we ''know'' that he owns ''none'') or "null" (we ''do not know'' how many he owns). In a database table, the Column (database), column reporting this answer would ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Cleansing
Data cleansing or data cleaning is the process of identifying and correcting (or removing) corrupt, inaccurate, or irrelevant records from a dataset, table, or database. It involves detecting incomplete, incorrect, or inaccurate parts of the data and then replacing, modifying, or deleting the affected data. Data cleansing can be performed interactively using data wrangling tools, or through batch processing often via scripts or a data quality firewall. After cleansing, a data set should be consistent with other similar data sets in the system. The inconsistencies detected or removed may have been originally caused by user entry errors, by corruption in transmission or storage, or by different data dictionary definitions of similar entities in different stores. Data cleaning differs from data validation in that validation almost invariably means data is rejected from the system at entry and is performed at the time of entry, rather than on batches of data. The actual process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Transformation
In computing, data transformation is the process of converting data from one format or structure into another format or structure. It is a fundamental aspect of most data integrationCIO.com. Agile Comes to Data Integration. Retrieved from: https://www.cio.com/article/2378615/data-management/agile-comes-to-data-integration.html and data management tasks such as data wrangling, data warehousing, data integration and application integration. Data transformation can be simple or complex based on the required changes to the data between the source (initial) data and the target (final) data. Data transformation is typically performed via a mixture of manual and automated steps.DataXFormer. Morcos, Abedjan, Ilyas, Ouzzani, Papotti, Stonebraker. An interactive data transformation tool. Retrieved from: http://livinglab.mit.edu/wp-content/uploads/2015/12/DataXFormer-An-Interactive-Data-Transformation-Tool.pdf Tools and technologies used for data transformation can vary widely based on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Wrangling
Data wrangling, sometimes referred to as data munging, is the process of transforming and mapping data from one " raw" data form into another format with the intent of making it more appropriate and valuable for a variety of downstream purposes such as analytics. The goal of data wrangling is to assure quality and useful data. Data analysts typically spend the majority of their time in the process of data wrangling compared to the actual analysis of the data. The process of data wrangling may include further munging, data visualization, data aggregation, training a statistical model, as well as many other potential uses. Data wrangling typically follows a set of general steps which begin with extracting the data in a raw form from the data source, "munging" the raw data (e.g. sorting) or parsing the data into predefined data structures, and finally depositing the resulting content into a data sink for storage and future use. It is closely aligned with the ETL process. Backg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Scraping
Data scraping is a technique where a computer program extracts data from Human-readable medium, human-readable output coming from another program. Description Normally, Data transmission, data transfer between programs is accomplished using data structures suited for Automation, automated processing by computers, not people. Such interchange File format, formats and Protocol (computing), protocols are typically rigidly structured, well-documented, easily parsing, parsed, and minimize ambiguity. Very often, these transmissions are not human-readable at all. Thus, the key element that distinguishes data scraping from regular parsing is that the data being consumed is intended for display to an End-user (computer science), end-user, rather than as an input to another program. It is therefore usually neither documented nor structured for convenient parsing. Data scraping often involves ignoring binary data (usually images or multimedia data), Display device, display formatting, red ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Web Crawler
Web crawler, sometimes called a spider or spiderbot and often shortened to crawler, is an Internet bot that systematically browses the World Wide Web and that is typically operated by search engines for the purpose of Web indexing (''web spidering''). Web search engines and some other websites use Web crawling or spidering software to update their web content or indices of other sites' web content. Web crawlers copy pages for processing by a search engine, which Index (search engine), indexes the downloaded pages so that users can search more efficiently. Crawlers consume resources on visited systems and often visit sites unprompted. Issues of schedule, load, and "politeness" come into play when large collections of pages are accessed. Mechanisms exist for public sites not wishing to be crawled to make this known to the crawling agent. For example, including a robots.txt file can request Software agent, bots to index only parts of a website, or nothing at all. The number of In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
