 Professor from Department of Electronics from Walton Institute of Technology, Sulappur. So today we are going to have a session on database languages and the interferences. At the end of this session student will be able to distinguish between the logical data independence, physical data independence and database languages and interferences. The concept of data independence which can be defined as a capacity to change the schema at one level of database system without having a change the schema at the next level. They are divided into two types logical data independence and physical data independence. Let's go one by one logical data independence. It is a capacity to change the conceptual schema without having to change the external schemas or the application programs. We may change the conceptual schema to expand the database like by adding records or data items to change the constraints or to reduce the database by removing a data record or the data item. External schemas that only refer to the remaining data should not be affected. For example, the external schema should not be affected by changing the grade report file. Only the view definition and the mapping needed to be changed in the database and that suppose the logical data independence. After the conceptual schema undergoes a logical reorganization, application programs that refer the external schema constructs must work as before. Changes to the constraints can be implemented to the conceptual schema without affecting the external schemas or the application programs. Next is the physical data independence. It is a capacity to change the internal schema without having to change the conceptual schema. Hence the external schemas need not to be changed as well. Changes to the internal schema can be needed because some physical files were reorganized. For example, by creating additional access structures, improving the performance of the retrieval or the update. Data independence is nothing but when you are going to change the logical schema, the physical schema should not get affected. So physical schema is what, how the data files are stored in physically or the file structures or the access path you can save. So whenever you are going to change the access path to the file in the logical schema, then the physical schema should not get affected. So physical schema is nothing but about the files, about the data constraints, about the catalogs and everything metadata. So whenever you are going to change the physical schema, the external view. So external view for the user should not get affected. So it says that whenever you are going to make changes in one schema, it should not get affected in the other schema. If the same data as before remains in the database, we should not to have the change in the conceptual schema. For example, providing access path to improve the retrieval and speed of section records by semester and year should not require any query, such as list of all the sections offered in the fall 2008 to change although the query should be executed more efficiently by the DBMS by utilizing the new access path. So we need to change the access path to increase the retrieval speed. So whenever you are changing the access path which is changing the physical schema, then it should not change the with the logical schema. Database must provide appropriate languages and interfaces for each category of users. DBMS languages. Once the design of the DBMS is completed and DBMS is chosen to implement the database, the first step is to specify conceptual and internal schemas for the database and mapping between them. In many DBMS, where no strict separation of levels is maintained, one language called the data definition language which is DDL is used by DBA. DBA is nothing but the database administrator and by data designers to define both the schemas. So database definition language, DDL language is used by the database administrators. The DBMS will have only DDL compiler whose function is to process DDL statements in order to identify descriptions of the schema constructs and to store the schema descriptions in the DBMS catalog. So DBMA users, they are going to use the data definition language, they are going to have the DDL statements which is given to the compilers and then it is given to the database catalogs where the information stored in the catalog. In DBMS, where a clear separation is maintained between the conceptual and internal schemas, the DDL is used to specify the conceptual schemas only. DDL is concerned with the conceptual schema only. Another language, the storage definition language which is the SDL is used to specify the internal schema. The mapping between the two schemas can be specified in either of the languages using the SDL language or using the DDL language. The internal schema is specified by combination of functions, parameters, specifications related to storage. This permit the DBMA staff to control indexing and mapping of the data to storage. The view definition language VDL to specify user views and mapping to the conceptual schema. The only database schemas are compiled and databases populated with the data. Users must have some of these to manipulate the data. Typical manipulations include the travel, insertion, deletion and modification of the data. DBMS provides a set of programs for the languages called data manipulation language, DML for these purposes. So let's go with the database interfaces one by one. Menu based interfaces for the web clients or the browsing. These interfaces provide the user with a list of options called menus. Delet the users through the formulation of the request. Menus do away with the need of memorization of the specific commands and syntaxes for the query language rather than queries composed of step by step picking up the options from the menus and displaying other stream. If you have gone through the ATM machine, there is a menu based interface for you. So you have to click on the withdrawal or you have to click for the saving account or the other account. You can say or you have to click for the pin and then enter then withdraw or deposit whatever it is. So there is an ATM machine has given you the menu based interferences. So this will minimize you with the memorization of the specific commands. So menu based are easiest one for the web browsing or the web clients you can say. Just clicking on the menus you have to select the commands or the queries. Pull down menus are very popular techniques in the web based or the user interferences. They are also often used in the browsing interfaces, which allow the user to look through the contents of the database in the exploratory and the unstructured manner. Next is the form based menus. So if ever if you have filled the Google form, so similarly your DBMS provides you the form based interferences. So that you have to just fill up the forms of the new data, whichever data you want to insert and then you can just retrieve the data with the remaining entries. Forms are usually designed and programmed for the navu users or the interfaces to the can transactions. Many DBMS have form specific languages, which are special languages that help the programmer specify such forms. So form yes you will provide you the form so that you can fill up the form and you can have the entries the new data to be inserted. SQL forms is an form based language that specifies the queries and even you have an oracle forms. Next is the graphic user interface. A GUI typically displays a schema to the user in a diagrammatic form. The user then can specify a query by manipulating the diagram. In many cases graphical user interfaces utilize both menus and forms. So graphical user interfaces provide you the combination of menus as well as forms. Most of the graphical user interfaces uses a pointing device such as mouse to select certain type of display schemas. Next is a natural language, which is nothing but the English language or the other language attempts to understand. So it also provides you the simple language, natural language feature to interface with the database. If the interpretation is successful, interface generates a high level query language through the natural language. So similarly in C program the English language which is your C language is converted into machine language which is understable by computer. So this similarly our English language is converted into high level query language and then executed by the DBMS software. Next is the speech input output. So limited use of speech as an input query and speech as an output query can also be used for the interfacing with the DBMS. Applications with a limited vocabulary such as inquiries for the telephone dictionary, flight arrival, credit, all these use the speech input output for interfacing with the DBMS. The speech input is detected using the library of predefined words that can be set up to parameters that can be, the speech input is detected using the library of predefined words and used to set up the parameters that are supplied to the queries. So these are the references of the database systems by Ramesh and the Shomkan B. Naute. Thank you.