Units 9 - 12 things that come up in exam!

Question 1

Give a scenario where you might use a signature and explain why it is appropriate?

Answer 1

Scenario: the recipient wants to check the sender’s identity.
Used in comms where little is at stake, where the recipient trusts the sender to self-authenticate.

Question 2

Give a scenario where you might use a certificate and explain why it is appropriate?

Answer 2

Scenario: the recipient wants a third party to check the identity of the sender.
Used where more confidential info is involved and it’s more important to authenticate the server.

Question 3

What are the main functions of the ORB in CORBA

Answer 3

• implementing an ORB service
• locating objects able to meet a software request
• preparing an object to receive a software request
• communicating data between two objects taking part in a software interaction.

Question 4

What is SOAP?

Answer 4

Simple Object Access Protocol, supports communication between heterogeneous systems.
- is the standard way of implementing web services
- uses XML which is platform independent
An XML based protocol supporting communicaton between distributed systems and widely used in web services.

Question 5

What are the main similarities between RMI and a system based on CORBA?

Answer 5

• both implement an object model
• both provide location and communication transparency
• both use stubs and skeletons to communicate a call and to marshall arguments
• ORB provides a service similar to RMI registry where references can be obtained by clients wishing to use them.
• both support passing objects by reference, enabling sending code to remote systems.

Question 6

What are the main differences between RMI and CORBA

Answer 6

• RMI is a programming technology while CORBA is an integration technology occupying spaces between programmes
• RMI is JVM specific, CORBA is CORBA compliant
• CORBA is more extensive offering additional services
• RMI is homogenous, CORBA implementation is heterogenous allowing integration of legacy systems
• RMI interface is JAVA, CORBA interface is Corba IDL
• RMI is synchronous while Corba is more varied

Question 7

What is the purpose of CORBA

Answer 7

specifies services that are of particular use in distributed systems

Question 8

What is more robust, synchronous or asynchronous communication?

Answer 8

Synchronous because it involves a ‘handshake’ which also provides an opportunity to recover from errors.

Question 9

Key similiarities in .NET and Java EE

Answer 9

• Application to enterprise systems and support for enterprise requirements such as transaction processing, web services, security SOAP/XML and CORBA.
• Both rely on an intermediate layer over the OS, JAVA runtime and CLR for .Net. this has speed implications, both rely on a Virtual machine.
• both rely on intermediate language, bytecode and CLI

Question 10

Key differences in .NET and Java EE

Answer 10

• .Net may be easier to integrate with legacy systems as it has a heterogenous implementation language
• Java has various IDEs while .Net is limited to MS Studie
  Java isopen source