The idea of Null was introduced into SQL to handle missing information in the relational model. The introduction of Null (or Unknown) along with True and False is the foundation of three-valued logic. Null does not have a value (and is not a member of any data domain) but is rather a placeholder or “mark” for missing information. Therefore comparisons with Null can never result in either True or False but always in the third logical result, Unknown. SQL uses Null to handle missing information.
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ISO/IEC 9126 Software engineering Product quality is an international standard for the evaluation of software quality
The quality model established in the first part of the standard, ISO/IEC 9126-1, classifies software quality in a structured set of characteristics and sub-characteristics as follows:
* Functionality – A set of attributes that bear on the existence of a set of functions and their specified properties. The functions are those that satisfy stated or implied needs.
* Reliability – A set of attributes that bear on the capability of software to maintain its level of performance under stated conditions for a stated period of time.
* Usability – A set of attributes that bear on the effort needed for use, and on the individual assessment of such use, by a stated or implied set of users.
* Efficiency – A set of attributes that bear on the relationship between the level of performance of the software and the amount of resources used, under stated conditions.
* Maintainability – A set of attributes that bear on the effort needed to make specified modifications.
* Portability – A set of attributes that bear on the ability of software to be transferred from one environment to another.
PMML is an XML-based language which provides a way for applications to define and share neural network models (and other data mining models) between PMML compliant applications. PMML provides applications a vendor-independent method of defining models so that proprietary issues and incompatibilities are no longer a barrier to the exchange of models between applications. It allows users to develop models within one vendor’s application, and use other vendors’ applications to visualize, analyze, evaluate or otherwise use the models. Previously, this was very difficult, but with PMML, the exchange of models between compliant applications is now straightforward.
Selenium-Grid allows the Selenium-RC solution to scale for large test suites or test suites that must be run in multiple environments. With Selenium-Grid, multiple instances of Selenium-RC are running on various operating system and browser configurations; Each of these when launching register with a hub. When tests are sent to the hub they are then redirected to an available Selenium-RC, which will launch the browser and run the test. This allows for running tests in parallel, with the entire test suite theoretically taking only as long to run as the longest individual test.
Selenium-IDE is the Integrated Development Environment for building Selenium test cases. It operates as a Firefox add-on and provides an easy-to-use interface for developing and running individual test cases or entire test suites. Selenium-IDE has a recording feature, which will keep account of user actions as they are performed and store them as a reusable script to play back. It also has a context menu (right-click) integrated with the Firefox browser, which allows the user to pick from a list of assertions and verifications for the selected location. Selenium-IDE also offers full editing of test cases for more precision and control.
Although Selenium-IDE is a Firefox only add-on, tests created in it can also be run against other browsers by using Selenium-RC and specifying the name of the test suite on the command line.
Selenium-RC allows the test automation developer to use a programming language for maximum flexibility and extensibility in developing test logic. For instance, if the application under test returns a result set, and if the automated test program needs to run tests on each element in the result set, the programming language’s iteration support can be used to iterate through the result set, calling Selenium commands to run tests on each item.
Selenium-RC provides an API (Application Programming Interface) and library for each of its supported languages: HTML, Java, C#, Perl, PHP, Python, and Ruby. This ability to use Selenium-RC with a high-level programming language to develop test cases also allows the automated testing to be integrated with a project’s automated build environment.
Selenium is a portable software testing framework for web applications. Selenium provides a record/playback tool for authoring tests without learning a test scripting language. Selenium provides a test domain specific language (DSL) to write tests in a number of popular programming languages, including C#, Java, Ruby, Groovy, Python, PHP, and Perl. Test playback is possible in most modern web browsers. Selenium deploys on Windows, Linux, and Macintosh platforms. Selenium provides a rich set of commands for fully testing your web-app in virtually any way you can imagine. The command set is often called selenese. These commands essentially create a testing language.
Selenium commands come in three “flavors”: Actions, Accessors and Assertions.
• Actions are commands that generally manipulate the state of the application. They do things like “click this link” and “select that option”. If an Action fails, or has an error, the execution of the current test is stopped.
• Accessors examine the state of the application and store the results in variables, e.g. “storeTitle”. They are also used to automatically generate Assertions.
• Assertions are like Accessors, but they verify that the state of the application conforms to what is expected. Examples include “make sure the page title is X” and “verify that this checkbox is checked”.
The Predictive Model Markup Language (PMML) is an XML-based markup language developed by the Data Mining Group (DMG) to provide a way for applications to define models related to predictive analytics and data mining and to share those models between PMML-compliant applications.
PMML provides applications a vendor-independent method of defining models so that proprietary issues and incompatibilities are no longer a barrier to the exchange of models between applications. It allows users to develop models within one vendor’s application and use other vendors’ applications to visualize, analyze, evaluate or otherwise use the models. Previously, this was very difficult, but with PMML, the exchange of models between compliant applications is straightforward. Since PMML is an XML-based standard, the specification comes in the form of an XML schema.
DML is the subset of SQL used to add, update and delete data:
INSERT adds rows (formally tuples) to an existing table, e.g.,:
INSERT INTO My_table
(field1, field2, field3)
VALUES
(‘test’, ‘N’, NULL);
UPDATE modifies a set of existing table rows, e.g.,:
UPDATE My_table
SET field1 = ‘updated value’
WHERE field2 = ‘N’;
DELETE removes existing rows from a table, e.g.,:
DELETE FROM My_table
WHERE field2 = ‘N’;
MERGE is used to combine the data of multiple tables. It combines the INSERT and UPDATE elements. It is defined in the SQL:2003 standard; prior to that, some databases provided similar functionality via different syntax, sometimes called “upsert”.
The most common operation in SQL is the query, which is performed with the declarative SELECT statement. SELECT retrieves data from one or more tables, or expressions.
A query includes a list of columns to be included in the final result immediately following the SELECT keyword. An asterisk (“*”) can also be used to specify that the query should return all columns of the queried tables. SELECT is the most complex statement in SQL, with optional keywords and clauses that include:
- The FROM clause which indicates the table(s) from which data is to be retrieved. The FROM clause can include optional JOIN subclauses to specify the rules for joining tables.
- The WHERE clause includes a comparison predicate, which restricts the rows returned by the query. The WHERE clause eliminates all rows from the result set for which the comparison predicate does not evaluate to True.
- The GROUP BY clause is used to project rows having common values into a smaller set of rows. GROUP BY is often used in conjunction with SQL aggregation functions or to eliminate duplicate rows from a result set. The WHERE clause is applied before the GROUP BY clause.
- The HAVING clause includes a predicate used to filter rows resulting from the GROUP BY clause. Because it acts on the results of the GROUP BY clause, aggregation functions can be used in the HAVING clause predicate.
- The ORDER BY clause identifies which columns are used to sort the resulting data, and in which direction they should be sorted (options are ascending or descending). Without an ORDER BY clause, the order of rows returned by an SQL query is undefined.