computer world

  Aggregation and  Functional dependency in  DBMS Aggregation  In aggregation the relation between two entities is treated as a single entity. In aggregation relationship with its corresponding entity is aggregated into higher level entity . It is the process of compiling information on object, there by obstructing a higher level. On limitation of the ER model is that it can not Express relationship among relationships. The aggregation represent a relationship between a whole object and its component in other word we can say that using aggregation we can express relationship main relationships.  For example center entity offer the course entity act as a single entity in the relationship which is in a relationship with another entity visitor. In the real world if a visitor visits a coaching center they will never inquiry about the course or just about the center instead he will ask the inquiry about both. Functional dependency  Functional dependency play an important role in differentia

  Distributed transaction model Distributed transaction model:- To access the various data items in a distributed system is usually e accomplished through transaction there are two type of transaction that we need to consider The local transaction The Global transaction    The local transaction:- The local transaction are those that access and update data is only one local database.  The global transaction:- global transaction are those that access and update data in several local database in the case of global transaction the task is more complicated since several nodes may be participating in execution the failure of a communication link connecting these nodes may result in erroneous computation.  System structure :- Each node has its oven local transaction manager whose function is to ensure those transaction that execute at that site. The various transaction manager corporate to execute global transaction. To understand how such a manager can be implemented we define and abstrac

 Nested relation   During the first normal form we require that all attributes have atomic domain a domain is atomic if elements of the domain are considered to be indivisible unit.  For example the set of integer is an atomic domain but the set of all sets of integer is a non atomic domain. We considered set of integer to have subpart the important issue in first normal form not the domain itself but rather the way we use domain element in database. The nested relational model is a extension of the relation model in which domain may be either atomic or relation  valued of a tuple on a attribute may be relation and relation may be stored within relation . A complex objects can be represented by a single tuple of a nested relation if we view a tuple of a nested relation a data item we have a one to one correspondence between data item and objects in the user's view of the database.  Nested relation are just one example of extensions to the basic relational model. The object oriented

   Database system vs file system                    pixabay    Data redundancy  it means duplication of data for more than one place. Like a customer detail like name, account number, address are stored at more than one place. In file system redundancy of data increase which consume more space and more difficult to maintain. By using DBMS we can reduce data duplication and update the data.  Insert and delete records  In file system we cannot insert and delete any particular record from data. DBMS provides faculty of deletion and also we can easily insert new record or data.  Difficult to search the data  In file system if we want to search popular record for example record of that customer who's minimum balance is 75000 in saving account so it is difficult to retrieve those data. But by using DBMS there are searching options are easily available.  Security problem  In file system there is very less or no security DBMS provides high level security mechanism like password,security,

     Difference between HTML and DHTML  HTML is a markup language, while DHTML is a collection of Technology.  DHTML creates dynamic web page, whereas HTML create static web page.  DHTML allow including small animations and dynamic menus in web pages but HTML is not able to do so.   HTML used events, methods, properties to insulate dynamism in HTML pages.   HTML is used to describe the web page but DHTML is a collection of JavaScript and style sheet in an HTML page. HTML sites will be show upon client side Technologies, while  DHTML site will be fast enough upon client side Technologies as most of entries are checked on browser itself and not waste time rendering to server for mistake.  HTML creates a plain web page without any style and scripts called as HTML. Whereas,  DHTML creates a page with HTML, CSS,DOM And scripts called as DHTML.  HTML cannot any server side code but XHTML may contain server side code.  HTML file are stored with .htm or .Html extension while DHTML file are sto

                                     What is DHTML  HTML stands for hypertext markup language and XHTML stands for dynamic HTML. HTML is basically a markup language used for creating tags but DHTML is not a language DHTML is web standard technology. XHTML is essentially dynamic HTML. It is a new way of looking at and controlling the standard HTML codes and commands. DHTML is a collection of technologies that are used to create interactive and animated website. DHTML gives more control over the the HTML elements. It allows one to incorporate a client side scripting language. Such as JavaScript, a representation definition language, such as CSS and the document object model in HTML web pages. DHTML also allows the pages to change at any time, without returning to the web server first. It allows scripting languages to change a web page look and function after the page has been fully loaded and during the viewing process. It also allows the user to add effects to their pages that are other