Problemas de pesquisa na internet

A Model of Learning Styles

NoSQL taxonomy

Some difference?

Abstraction

Classification of Data Structure

the trade-off between time and space

In computer science curricula, a common theme is the trade-off between time and space. In order to have a fast-running pro- gram, you may need to use more memory space. On the other hand, in order to conserve memory space, you might need to settle for slower code.

Classification and List of Patterns

Creational Patterns

•  Abstract factory: Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
•  Builder: Separate the construction of a complex object from its representation allowing the same construc- tion process to create various representations.
•  Factory method: Define an interface for creating an object, but let subclasses decide which class to instanti- ate. Factory Method lets a class defer instantiation to subclasses.
•  Lazy initialization: Tactic of delaying the creation of an object, the calculation of a value, or some other ex- pensive process until the first time it is needed.
•  Multiton: Ensure a class has only named instances, and provide global point of access to them.
•  Object pool: Avoid expensive acquisition and release of resources by recycling objects that are no longer in use. Can be considered a generalization of connection pool and thread pool patterns.
•  Prototype: Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.
•  Resource acquisition is initialization: Ensure that resources are properly released by tying them to the life-span of suitable objects.
•  Singleton: Ensure a class has only one instance, and provide a global point of access to it.

Structural Patterns

•  Adapter or Wrapper: Convert the interface of a class into another interface clients expect. Adapter lets classes work together that could not otherwise because of incompatible interfaces.
•  Bridge: Decouple an abstraction from its implementation allowing the two to vary independently.
•  Composite: Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.
•  Decorator: Attach additional responsibilities to an object dynamically keeping the same interface. Decorators provide a flexible alternative to subclassing for extending functionality.
•  Facade: Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use.
•  Front Controller: Provide a unified interface to a set of interfaces in a subsystem. Front Controller defines a higher-level interface that makes the subsystem easier to use.
•  Flyweight: Use sharing to support large numbers of fine-grained objects efficiently.
•  Proxy: Provide a surrogate or placeholder for another object to control access to it. 

Behavioral Patterns

•  Blackboard: Generalized observer, which allows multiple readers and writers. Communicates information system-wide.
•  Chain of responsibility: Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.
•  Command: Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
•  Interpreter: Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.
•  Iterator: Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
•  Mediator: Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.
•  Memento: Without violating encapsulation, capture and externalize an object’s internal state allowing theobject to be restored to this state later.
•  Null object: Avoid null references by providing a default object.
•  Observer or Publish/subscribe: Define a one-to-many dependency between objects where a state change in one object results with all its dependents being notified and updated automatically.
•  Servant: Define common functionality for a group of classes.
•  Specification: Recombinable business logic in a Boolean fashion.
•  State: Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.
•  Strategy: Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
•  Template method: Define the skeleton of an algorithm in an operation, deferring some steps to subclasses.
• Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.
•  Visitor: Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.

Concurrency Patterns

•  Active Object: Decouples method execution from method invocation that reside in their own thread of con- trol. The goal is to introduce concurrency, by using asynchronous method invocation and a scheduler for handling requests.
•  Balking: Only execute an action on an object when the object is in a particular state.
•  Binding Properties: Combining multiple observers to force properties in different objects to be synchronized or coordinated in some way.
•  Messaging pattern: The messaging design pattern (MDP) allows the interchange of information (i.e. messages) between components and applications.
•  Double-checked locking: Reduce the overhead of acquiring a lock by first testing the locking criterion (the “lock hint”) in an unsafe manner; only if that succeeds does the actual lock proceed. Can be unsafe when implemented in some language/hardware combinations. It can therefore sometimes be considered an anti-pat- tern.
•  Event-based asynchronous: Addresses problems with the Asynchronous pattern that occur in multithreaded programs.
•  Guarded suspension: Manages operations that require both a lock to be acquired and a precondition to be satisfied before the operation can be executed.
•  Lock: One thread puts a “lock” on a resource, preventing other threads from accessing or modifying it.
•  Monitor object: An object whose methods are subject to mutual exclusion, thus preventing multiple objects from erroneously trying to use it at the same time.
•  Reactor: A reactor object provides an asynchronous interface to resources that must be handled synchronously.
•  Read-write lock: Allows concurrent read access to an object but requires exclusive access for write operations.
•  Scheduler: Explicitly control when threads may execute single-threaded code.
•  Thread pool: A number of threads are created to perform a number of tasks, which are usually organized in a queue. Typically, there are many more tasks than threads. Can be considered a special case of the object pool pattern.
•  Thread-specific storage: Static or “global” memory local to a thread.

Data Access Patterns

•  ORM Patterns: Domain Object Factory, Object/Relational Map, Update Factory.
•  Resource Management Patterns: Resource Pool, Resource Timer, Retryer, Paging Iterator.
•  Cache Patterns: Cache Accessor, Demand Cache, Primed Cache, Cache Collector, Cache Replicator.

Enterprise Patterns

•  Presentation Tier Patterns: Intercepting Filter, Front Controller, View Helper, Composite View, Service to Worker, Dispatcher View.
•  Business Tier Patterns: Business Delegate, Value Object, Session Facade, Composite Entity, Value Object Assembler, Value List Handler, Service Locator.
•  Integration Tier Patterns: Data Access Object, Service Activator.

Real-Time Patterns

•  Architecture Patterns: Layered Pattern, Channel Architecture Pattern, Component-Based Architecture, Recursive Containment Pattern and Hierarchical Control Pattern, Microkernel Architecture Pattern, Virtual Machine Pattern.
•  Concurrency Patterns: Message Queuing Pattern, Interrupt Pattern, Guarded Call Pattern, Rendezvous Pattern, Cyclic Executive Pattern, Round Robin Pattern.
•  Memory Patterns: Static Allocation Pattern, Pool Allocation Pattern, Fixed Sized Buffer Pattern, Smart Pointer Pattern, Garbage Collection Pattern, Garbage Compactor Pattern.
•  Resource Patterns: Critical Section Pattern, Priority Inheritance Pattern, Priority Ceiling Pattern, Simultaneous Locking Pattern, Ordered Locking Pattern.
•  Distribution Patterns: Shared Memory Pattern, Remote Method Call Pattern, Observer Pattern, Data Bus Pattern, Proxy Pattern, Broker Pattern.
•  Safety and Reliability Patterns: Monitor-Actuator Pattern, Sanity Check Pattern, Watchdog Pattern, Safety Executive Pattern, Protected Single Channel Pattern, Homogeneous Redundancy Pattern, Triple Modular Redundancy Pattern, Heterogeneous Redundancy Pattern.

Some key figures that have influenced thinking about research

• Plato (427–347 BC) and Aristotle (348–322 BC) – these represent the two contrasting approaches to acquiring knowledge and understanding the world (epistemology). Plato argued for deductive thinking (starting with theory to make sense of what we observe) and Aristotle for the opposite, inductive thinking (starting with observations in order to build theories).
• René Descartes (1596–1650) – provided the starting point for modern philosophy by using a method of systematic doubt; that we cannot rely on our senses or logic, and therefore he challenged all who sought for the basis of certainty and knowledge. His famous maxim is ‘I think, therefore I am’, that is – I can only be sure of my own existence, the rest must be doubted.
• John Locke (1632–1704) – made the distinction between bodies or objects that can be directly measured, and therefore have a physical existence, and those abstract qualities that are generated by our perceptions and feelings.
• George Berkeley (1685–1753) – argued that all things that exist are only mental phenomena. They exist by being perceived. This is ‘our’ world.
• David Hume (1711–1776) – made a distinction between systems of ideas that can provide certainty – e.g. maths – and those that rely on our perceptions (empirical evidence) which are not certain. He recognized the importance of inductive thinking in the advancement of scientific knowledge, but highlighted its restrictions in finding the truth.
• Immanuel Kant (1724–1804) – held that our minds organize our experiences to make sense of the world. Therefore ‘facts’ are not independent of the way we see things and interpret them.
• Karl Popper (1902–1994) – formulated a combination of deductive and inductive thinking in the hypothetico-deductive method, commonly known as scientific method. This method aims to refine theories to get closer to the truth.
• Auguste Compte (1789–1857) – maintained that society can be analysed empirically just like any other subjects of scientific enquiry. Social laws and theories are based on psychology and biology.
• Karl Marx (1818–1883) – defined moral and social aspects of humanity in terms of material forces.
• Emil Durkheim (1858–1917) – argued that society develops its own
• system of collectively shared norms and beliefs – these were ‘social facts’.
• Max Weber (1864–1920) – insisted that we need to understand the values and meanings of subjects without making judgements – ‘verstehen’ was the term he coined for this which is German for ‘understanding’.
• Thomas Kuhn (1922–1995) – revealed that scientific research cannot be separated from human influences and is subject to social norms.
• Michel Foucault (1926–1984) – argued that there was no progress in science, only changing perspectives, as the practice of science is shown to control what is permitted to count as knowledge. He demonstrated how discourse is used to make social regulation and control appear natural.
• Jacques Derrida (1930–2004) – stated that there is no external or fixed meaning to text, nor is there a subject who exists prior to language and to particular experiences. You cannot get outside or beyond the structure. This approach led to the movement called Deconstruction.