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How can we Classify the operations on classes
This step fundamentally means all three models functional, object and dynamic (studied in last section) must be combined so that we can know what operations are to be performed on objects.
We can design a state diagram describing life history of an object. A transition is a change of the state of object and it maps into an operation on object. It helps in imagining state changes. We could associate an operation with every event received by an object. Also, sometimes an event might represent an operation on other objects too that is where one event triggers another event. Therefore, in this case, event pair must be mapped into an operation performing action and returning control provided which the events are on a single thread of control passing from one object to another object.
Explain the Deferred Update The deferred update methods do not physically update the database on disk till after a transaction reaches its commit point; after that the updates
explaination
Domain Constraints Domain constraints are primarily formed for defining the logically correct values for an attribute of a relation. The relation allows attributes of a relatio
Define the terms entity, attribute, role and relationship between the entities, giving examples for each of them. Ans: Entity: An entity is a "thing" or "object" in th
Timestamps For Read operations: If TS (T) If TS (T) >= W-timestamp (Q), then the transaction T is trying to read a value of data item Q which has been written and committed
How does a query tree represent a relational algebra expression? Discuss any three rules for query optimisation, giving example as to when should each rule be applied. Ans
Introduction In large projects, we can have many different companies working together. Generally, the project or contract is awarded to one company (Principal Contractor), which
We are looking to find someone to prepare a database which improves upon the one we are using at present. The present database will be found here: Click on filter options and yo
Attribute Preservation This is a easy and obvious necessity that includes preserving all the attributes that were there in the relation that is being decomposed.
Consider the entity type dependent related to employee entity, which is used to keep track of the dependents of every employee. The attributes of dependents are: name, sex, birth d
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