Middleware

Question 1

What is the primary purpose of middleware in modern distributed systems?

Answer 1

To operate as an intermediate layer between OS layer and application layer to facilitate component interaction

Question 2

What transparency-related function does middleware provide?

Answer 2

It abstracts away the complexity of network programming

Question 3

What is the scalability aspect of middleware?

Answer 3

It handles large numbers of components and supports dynamic resource allocation and load balancing

Question 4

What does openness mean in middleware context?

Answer 4

Support for heterogeneous components developed with different technologies and platform independence

Question 5

What is adaptivity in middleware systems?

Answer 5

The ability to handle dynamic component joining and leaving without relying on a priori information

Question 6

What is context-awareness in middleware?

Answer 6

The ability to dynamically retrieve environmental information and adapt to environmental dynamics

Question 7

What are the main components of Remote Method Invocation (RMI)?

Answer 7

Stub (Client-side proxy), Skeleton (Server-side handler), and Registry for service lookup

Question 8

What is the role of a stub in RMI?

Answer 8

It acts as a client-side proxy for method invocation

Question 9

How does attribute-based discovery differ from traditional naming service?

Answer 9

It uses a set of attributes instead of simple names for service discovery

Question 10

What are the three subscription models in event-based middleware?

Answer 10

Topic-based, Content-based, and Type-based

Question 11

What is the difference between synchronous and asynchronous notification in event-based models?

Answer 11

Synchronous provides immediate delivery, while asynchronous uses queued delivery

Question 12

What is the main benefit of asynchronous notification?

Answer 12

It offers space and time decoupling, allowing components to exist on different networks at different times

Question 13

What are the main data types supported in shared dataspace models?

Answer 13

Simple variables, Tuples, Objects, Structured files, and Binary files

Question 14

What are the three main data access operations in shared dataspace models?

Answer 14

Put (write), Read (non-destructive), and Take (destructive)

Question 15

What is the main advantage of shared dataspace models?

Answer 15

Space and time uncoupling, plus nice representation of common context for interactions

Question 16

What is the main drawback of shared dataspace models?

Answer 16

Components may have to actively poll the dataspace to understand what’s happening

Question 17

What are the advantages of centralized middleware implementation?

Answer 17

Simple implementation, consistent state, and easy maintenance

Question 18

What are the disadvantages of centralized middleware implementation?

Answer 18

Single point of failure, limited scalability, and performance bottleneck

Question 19

What are the coordination policies in distributed middleware implementation?

Answer 19

Hierarchical distribution, Global replication, Request forwarding, and Partial replication

Question 20

What are the advantages of distributed middleware implementation?

Answer 20

High availability, better scalability, and fault tolerance

Question 21

What are the challenges of distributed middleware implementation?

Answer 21

Consistency maintenance, synchronization overhead, and complex implementation

Question 22

What is CORBA?

Answer 22

Common Object Request Broker Architecture - a pioneering middleware technology for distributed computing across different platforms

Question 23

What is .NET Framework’s role in middleware?

Answer 23

Microsoft’s comprehensive approach to enterprise middleware for building and deploying distributed applications

Question 24

What are the main open issues in middleware?

Answer 24

User-aware services, Pervasive Computing Integration, Semantic Services, Autonomic Computing, and Multi-agent Systems