Architecture Styles in Software Design

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Questions and Answers

What is a primary function of a publish-subscribe architecture?

To facilitate real-time data sharing among distributed systems (correct)

To store data in a linear structure

To enhance data security through encryption

To create a direct connection between data producers and consumers

In the provided example, what is the purpose of the `linda.universe._out()` function?

To connect to the Linda tuple space

To remove data from the tuple space

To add data to a shared space accessible by all subscribers (correct)

To retrieve data from Alice's session

Which of the following best describes the role of `blog` in the example provided?

A data structure that exclusively belongs to Alice

An instance of a tuple space where messages are stored (correct)

A method for synchronizing network messages

A programming library for generating random messages

What does the `linda.universe._rd()` function do in the context of the publish-subscribe system?

It indicates a request to read a data tuple without removing it Signup and view all the answers

What aspect of the publish-subscribe model is illustrated by multiple messages being sent from different users, such as Bob and Alice?

It allows users to send unordered and independent messages to the same topic Signup and view all the answers

What is a primary characteristic of service-oriented architecture?

Interfaces and the objects that implement them can exist on different machines. Signup and view all the answers

Which statement accurately describes RESTful architecture?

Resources are identified through a single naming scheme. Signup and view all the answers

What operation in REST is used to create a new resource?

PUT Signup and view all the answers

After executing an operation on a service in a RESTful architecture, what does that component do regarding the caller?

Forgets all information about the caller. Signup and view all the answers

Which of these options represents a common operation in a RESTful architecture?

DELETE - Removes a resource. Signup and view all the answers

Which best describes the essence of resource-based architectures?

They view a distributed system as a collection of resources managed individually. Signup and view all the answers

In the context of RESTful architectures, what does the POST operation do?

Modifies an existing resource by transferring a new state. Signup and view all the answers

Which statement is NOT true about buckets in RESTful architectures?

Buckets can contain other buckets. Signup and view all the answers

What is a key characteristic of layered architecture?

Strong dependency between different layers Signup and view all the answers

Which of the following is considered a bad example of layered architecture?

Applications developed with little concern for stability Signup and view all the answers

In service-oriented architectures, what is true about the entities encapsulating services?

They operate as separate, independent entities. Signup and view all the answers

What is a drawback of poorly designed layered architectures?

Complicated inter-layer dependencies Signup and view all the answers

Which aspect is highlighted in the description of service-oriented architectures?

Encapsulation of independent services Signup and view all the answers

How do objects in an object-based architecture communicate with each other?

Through procedure calls Signup and view all the answers

What is a primary advantage of well-designed layered architecture?

It reduces the interaction complexity across layers. Signup and view all the answers

What defines the essence of an object-based style of architecture?

Objects executing across various networks Signup and view all the answers

What does coordination primarily involve in a process-oriented context?

Communication and cooperation between processes Signup and view all the answers

What type of coupling requires processes to be available at the same time?

Temporal coupling Signup and view all the answers

Which type of coupling allows processes to communicate without needing to know each other’s identifiers?

Referentially decoupled coupling Signup and view all the answers

In a publish-subscribe architecture, what is an example of referentially coupled communication?

Direct communication Signup and view all the answers

Which operation does NOT involve blocking in the Linda tuple space model?

o u t (t) Signup and view all the answers

What characterizes the underlying structure of a tuple space in the Linda model?

It is modeled as a multiset Signup and view all the answers

What does the i n (t) operation do in the Linda tuple space?

Removes a tuple matching a template Signup and view all the answers

What is the main purpose of the o u t (t) operation in the Linda tuple space?

To add a tuple to the tuple space Signup and view all the answers

What is the main purpose of the publish-subscribe architecture in distributed systems?

To match events through specified attribute-value pairs. Signup and view all the answers

Which of the following describes a potential issue with content-based subscriptions?

They may encounter serious scalability problems. Signup and view all the answers

What role does middleware play in distributed systems?

It acts as the operating system for distributed applications. Signup and view all the answers

What is an example of an application of the publish-subscribe architecture?

Real-time messaging platforms. Signup and view all the answers

Which component is NOT typically included in middleware?

Direct application business logic. Signup and view all the answers

How does topic-based subscription differ from content-based subscription?

Topic-based specifies a series of attribute-value pairs, while content-based specifies ranges of attributes. Signup and view all the answers

What can be deduced about the user 'Alice' in the provided code?

Alice is associated with the topic 'gtcn'. Signup and view all the answers

Which are the components provided by middleware in distributed systems?

Inter-application communication, security, and failure recovery. Signup and view all the answers

Study Notes

Layered Architectures

Frequently used architectural style
Can be a drawback if not well-designed as layers can be dependent on each other
Best examples are communication protocol stacks
Poorly designed applications use pre-built components without regard for stable interfaces and overlapping functionality

Service-Oriented Architectures

Composed of multiple independent, separate entities, each encapsulating and executing services as a separate process or thread, also called objects.
Object-based styles encapsulate data internally while offering methods for external access without revealing internal structure.
Interfaces are separated from implementing objects allowing for interface placement on a different machine than the object itself.
Distributed Resource Based architectures utilize a collection of resources managed by components, that can be added, removed, retrieved and modified by remote applications.
RESTful architectures are resource-based architectures that utilizes the same interface for all services, resources are individually identifiable, messages are self-described, and calls are forgotten after completion.
PUT operations create a new resource, GET operations retrieve the state of a resource, DELETE operations delete resources, and POST operations modify existing resources, transferring a new state.
Amazon Simple Storage Service is an example of RESTful architecture that stores objects/files in buckets (directories).

Coordination Models

Coordination encompasses the communication and cooperation between different processes.
Temporal and Referential coupling between processes exist. Temporal coupling requires processes to be available at the same time. Referential coupling requires processes to know the names or identifiers of other processes.
Coupling can be either direct, mailbox, event-based, or shared data space.

Both event-based and shared data space are forms of publish-subscribe architectures.
Tuple space is a shared data space example that uses the Linda programming language.
Tuple space uses three operations to access data: i n ( t ) to remove a matching tuple, r d ( t ) to obtain a copy of a matching tuple, and o u t ( t ) to add a tuple.
i n and r d are blocking operations, meaning they are waiting until a match is found.
Both publishers and subscribers use the universe object to access tuples.

Events can be matched based on their attributes and values, with the use of topic-based or content-based subscriptions.
Topic-based subscriptions use attribute = value pairs to match events.
Content-based subscriptions use attribute ∈ range pairs to match events.
Content-based subscriptions can negatively impact scaling.

Middleware

Middleware is critical to operating distributed systems.
Middleware is a collection of commonly used components and functions that applications typically do not need to implement separately.
These components include: inter-application communication abilities, security services, accounting services, masking and recovery from failures.

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Description

This quiz covers key concepts related to Layered Architectures and Service-Oriented Architectures in software design. It explores their characteristics, advantages, and potential drawbacks. Understanding these architectural styles is crucial for building efficient and well-structured applications.