Originis of oop: Polymorphism of Operations (Operator Overloading). Another characteristic of OO systems in general is that they provide for polymorphism of operations, which is also known as operator overloading. This concept allows the same operator name or symbol to be bound to two or more different implementations of the operator, depending on the type of objects to which the operator is applied. Multiple Inheritance and Selective Inheritance. Multiple inheritance occurs when a certain subtype T is a subtype of two (or more) types and hence inherits the functions (attributes and methods) of both supertypes. For example,we may create a subtype ENGINEERING_MANAGER that is a subtype of both MANAGER and ENGINEER. Selective inheritance occurs when a subtype inherits only some of the functions of a supertype. Other functions are not inherited Charactrstc of ood: an ODMS provides a unique identity to each independent object stored in the database. This unique identity is typically implemented via a unique, system-generated object identifier (OID).Immutable – They do not change. An OID can be used only once.The main property required of an OID is that it be immutable; that is, the OID value of a particular object should not change. an ODMS must have some mechanism for generating OIDs and preserving the immutability property. It is also desirable that each OID be used only once; that is, even if an object is removed from the database, its OID should not be assigned to another object. These two properties imply that the OID should not depend on any attribute values of the object, since the value of an attribute may be changed or corrected. . The three most basic CONSTRUCTORS are ATOM, STRUCT (or tuple), and COLLECTION. . One type constructor has been called the atom constructor. This includes the basic built-in data types of the object model, which are similar to the basic types in many programming languages: integers, strings, floating point numbers, enumerated types, Booleans, and so on. They are called single-valued or atomic types, since each value of the type is considered an atomic (indivisible) single value. A second type constructor is referred to as the struct (or tuple) constructor. This can create standard structured types, such as the tuples (record types) in the basic relational model. Collection (or multivalued) type constructors include the set(T), list(T), bag(T), array(T), and dictionary(K,T) type constructors. These allow part of an object or literal value to include a collection of other objects or values when needed. These constructors are also considered to be type generators Transient objects exist in the executing program and disappear once the program terminates. Persistent objects are stored in the database and persist after program termination. The typical mechanisms for making an object persistent are naming and reachability.An extent is a named persistent object whose value is a persistent collection that holds a collection of objects of the same type that are stored permanently in the database. The objects can be accessed and shared by multiple programs. It is also possible to create a transient collection, which exists temporarily during the execution of a program but is not kept when the program terminates. Polymorphism and operator overloading. Operations and method names can be overloaded to apply to different object types with different implementations.Polymorphism of Operations (Operator Overloading). Another characteristic of OO systems in general is that they provide for polymorphism of operations, which is also known as operator overloading. This concept allows the same operator name or symbol to be bound to two or more different implementations of the operator, depending on the type of objects to which the operator is applied. Semantics is the study of meaning in language. It can be applied to entire texts or to single words. The semantics of a relation refers to its meaning resulting from the interpretation of attribute values in a tuple. Design a schema that can be explained easily relation. The semantics of attributes should be easy to interpret. Anomalies: Database anomalies are the problems in relations that occur due to redundancy in the relations. These anomalies affect the process of inserting, deleting, and modifying. Insert Anomalies: An Insert Anomaly occurs when certain attributes cannot be inserted into the database without the presence of other attributes. For example - we can't add a new course unless we have at least one student enrolled on the course. Delete Anomalies:A Delete Anomaly exists when certain attributes are lost because of the deletion of other attributes. For example, consider what happens if Student S30 is the last student to leave the course All information about the course is lost. Modification Anomalies:An Update Anomaly exists when one or more instances of duplicated data is updated, but not all. For example, consider Jones moving address - you need to update all instances of Jones's address. Problems with NULLs: Wasted storage space, Problems understanding meaning,Avoid placing attributes in a base relation whose values may frequently be NULL, If NULLs are unavoidable, Make sure that they apply in exceptional cases only, not to a majority of tuples A spurious tuple is, basically, a record in a database that gets created when two tables are joined badly. In database-ese, spurious tuples are created when two tables are joined on attributes that are neither primary keys nor foreign keys. Spurious tuples: Tuples generated by joining two relations on attributes that are not keys or foreign keys on these relations.How can spurious tuples be prevented? If original relations are separated using the primary key. This will enforce the join to be on primary/foreign keys. OBJECTS and LITERALS are the basic building blocks of the object model. The main difference between the two is that an object has both an object identifier and a state (or current value), whereas a literal has a value (state) but no object identifier In either case, the value can have a complex structure. An object has five aspects: identifier, name, lifetime, structure, and creation. 1.The object identifier is a unique system-wide identifier 
Every object must have an object identifier. 
2.Some objects may optionally be given a unique name within a particular ODMS—this name can be used to locate the object, and the system should return the object given that name. 3.
 The lifetime of an object specifies whether it is a persistent object). Lifetimes are indepen- dent of types—that is, some objects of a particular type may be transient whereas others may be persistent.4 The structure of an object specifies how the object is constructed By using the type constructors. The structure specifies whether an object is atomic or not. 5. Object creation refers to the manner in which an object can be created. There are three types of LITERALS: atomic, structured, and collection. Atomic literals correspond to the values of basic data types and are prede- fined. The basic data types of the object model include long, short, and unsigned integer numbers. Structured literals correspond roughly to values that are constructed using the tuple constructor .3. Collection literals specify a literal value that is a collection of objects or val- ues but the collection itself does not have an Object_id. Functional dependency:A functional dependency is a constraint (associated with table) between two sets of attributes from the database. Ex. If R is a relation with attributes X and Y, a functional dependency between the attributes is represented as X->Y, which specifies Y is functionally dependent on X. Functional dependency is a property of the semantics or meaning of the attribute,The relation extensions that satisfy the functional dependency constrains are called legal relation states of R,The main use of functional dependency is to describe for a relation schema R by specifying constrains on its attributes t hat must hold at all times.,A functional dependency of the relation schema(R), not of a particular legal relation state r of R . Primary storage media can be operated on directly by the computer’s central processing unit (CPU), such as the computer’s main memory and smaller but faster cache memories whereas secondary storage ‘s Data cannot be processed directly by the CPU; first it must be copied into primary storage and then processed by the CPU. Primary storage usually provides fast access to data but is of limited storage capacity. they are still more expensive and have less storage capacity Secondary storage devices usually have a larger capacity, cost less, and provide slower access to data than do primary storage devices.Data in secondary or tertiary storage cannot be processed directly by the CPU; first it must be copied into primary storage and then processed by the CPU. Ex ps: This category includes magnetic disks, optical disks (CD-ROMs, DVDs, and other similar storage media), and tapes. Ex ss: Hard-disk drives are classified as secondary storage The main goal of RAID is to even out the widely different rates of performance improvement of disks against those in memory and microprocessors.12While RAMcapacities have quadrupled every two to three years, disk access times are improving at less than 10 percent per year, and disk transfer rates are improving at roughly 20percent per year. Disk capacities are indeed improving at more than 50 percent peryear, but the speed and access time improvements are of a much smaller magnitude.A second qualitative disparity exists between the ability of special microprocessors that cater to new applications involving video, audio, image, and spatial data processing, with corresponding ack of fast access to large, shared data sets.The natural solution is a large array of small independent disks acting as a singlehigher-performance logical disk. A concept called data stripingis used, which utilizesparallelism to improve disk performance. Data striping distributes data transparently over multiple disks to make them appear as a single large, fast disk. In SQL the following types of PRIVILAGES can be granted on each individual relation R: SELECT (retrieval or read) privilege on R. Gives the account retrieval privilege. In SQL this gives the account the privilege to use the SELECT statement to retrieve tuples from R. Modification privileges on R. This gives the account the capability to modify the tuples of R. In SQL this includes three privileges: UPDATE, DELETE, and INSERT. These correspond to the three SQL commands for modifying a table R. Additionally, both the INSERT and UPDATE privileges can specify that only certain attributes of R can be modified by the account. References privilege on R. This gives the account the capability to reference(or refer to) a relation R when specifying integrity constraints. This privilege can also be restricted to specific attributes of R. GRANT is a command used to provide access or privileges on the database objects to the users. grant a user edit privileges (SELECT, UPDATE, INSERT, and DELETE), which allows the user to both view and modify the contents of a dataset. In SQL the following types of privileges can be granted on each individual relation R: SELECT (retrieval or read) privilege on R. , Modification privileges on R. , References privilege on R. The REVOKE command removes user access rights or privileges to the database objects. In some cases it is desirable to grant a privilege to a user temporarily. For example, the owner of a relation may want to grant the SELECT privilege to a user for a specific task and then revoke that privilege once the task is completed. Hence, a mechanism for revoking privileges is needed. In SQL a REVOKE command is included for the purpose of cancelling privileges. DIFF OF IR and Databases : 1.Structured data 
2.Schema driven 
3.Relational (or object, hierarchical, and 
network) model is predominant 
4.Structured query model 
 5. Rich metadata operations 
 6.Query returns data 
 7. Results are based on exact matching (always 
correct) 
 IR Systems : 1.Unstructured data 
 2.No fixed schema; various data models 
(e.g., vector space model) 
3.Free-form query models 
4.Rich data operations 
5.Search request returns list or pointers to 
documents 
6. Results are based on approximate matching 
and measures of effectiveness (may be imprecise and ranked)