What are the similarities and differences between RMI and CORBA?

Similarities

Hide communication to remote objects behind method calls
Use stub/skeleton approach
Provide a Naming Service
Differences

RMI is Java-only, CORBA is multi-language
CORBA is more sophisticated - will have greater overhead
CORBA offers many additional services e.g. persistence, events, application-domain services.

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What is the role of an interface in CORBA?

An interface is used to define the services (methods) provided by an object and their parameters and results. The remote server provides an object which implements the interface. The client requests the interface from the ORB and the returned object must provide all the methods defined in the contract represented by the interface.

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What are the roles of a skeleton and a stub in CORBA?

A stub and a skeleton are automatically generated from the IDL description of an interface. The stub behaves to the caller just like the called object - it provides the same methods and implements the same interfaces. However, when the methods are called, the stub interacts with the network to pass the request to the skeleton. The skeleton calls the appropriate method on the called object and passes the results back to the stub, which returns them to the caller.


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What is the purpose of a request in CORBA?

A request is used to transfer the name of the method (the service) and the parameters between the client and the server.

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What is an ORB?

An ORB or Object Request Broker is software that allows servers to register the objects they provide and clients to find objects providing the services they want and then to interact with them.


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What is a heterogeneous distributed system?

A collection of communicating machines running different operating systems.


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What are the goals of CORBA?

CORBA aims to allow interaction between potentially distributed component objects created by different manufacturers in different languages (location transparency and language transparency).


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What is CORBA?

Common Object Request Broker Architecture - provides services to support intercommunication between objects. It is a framework and a specification for object collaboration and sharing across a heterogeneous distributed network of machines and applications.

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How do I copy files?

Using the cd command, move to the directory that contains the file you wish to copy.
Type a command similar to the below command.

cp myfile.txt \usr\bin

In the above example, you would substitute "myfile.txt" with the name of the file you wish to copy, and "\usr\bin" with the directory you're copying to.


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How do I find text within files in Linux?

One of the easiest methods of locating text contained within a file on a computer running Linux is to use the grep command. Below is a basic example of a command used to locate any htm file containing the word "help".

grep "help" *.htm


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How do I delete a file or folder?

Linux / Unix users can delete files through the console by using the rm command.

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How to create a directory / folder?

To create a directory in Linux, Unix, or any variant through the shell, use the mkdir Linux / Unix command.

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How do I find files in Linux / Unix?

Linux / Unix and their variants have several different ways of locating files. See each of the below commands for additional information about the command and how they can be used to locate files.

find
locate
wheris
which.

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DOS VS. Unix

Commands in DOS and Unix

DOS Unix

attrib chmod
backup tar
dir ls
cls clear
copy cp
del rm
deltree rm -R rmdir
edit vi pico
format fdformat mount umount
move / rename mv
type less
cd cd chdir
more < file more file
md mkdir
win startx



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How, exactly, do XML and SGML differ?

First of all, XML leaves out many features of SGML There are a few areas where XML and SGML really differ:
XML's white space handling rules are much less elaborate than those of SGML. One effect is that in a few, rarely-encountered, cases, an XML processor will pass through a some white space (mostly line-ends) that an SGML processor will suppress. It is very unlikely that an XML author or user will ever notice this.
XML defines, for documents, the property of being well-formed; this does not really correspond to any SGML concept.
XML has a very specific built-in method for handling international (non-ASCII) text. It is compatible with SGML, but at the moment, few SGML processors are properly internationalized.

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Is XML HTML?

No. An XML processor can read clean, valid, HTML, and with a few small changes an HTML browser like Netscape Navigator or Microsoft Internet Explorer would be able to read XML (the designers of XML would really like the authors of Navigator and Internet Explorer to make those changes).
The biggest difference between XML and HTML is that in XML, you can define your own tags for your own purposes, and if you want, share those tags with other users.

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Is XML SGML?

Yes. XML has been carefully designed with the goal that every valid XML document should also be an SGML document. There are some areas of difference between XML and SGML, but these are minor, should not cause practical problems, and will almost certainly reconciled with SGML in the near future.

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the steps necessary to parse XML documents?

Superficially, this is a fairly basic question. However, the point is not to determine whether candidates understand the concept of a parser but rather have them walk through the process of parsing XML documents step-by-step. Determining whether a non-validating or validating parser is needed, choosing the appropriate parser, and handling errors are all important aspects to this process that should be included in the candidate's response.

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What is SOAP and how does it relate to XML?

The Simple Object Access Protocol (SOAP) uses XML to define a protocol for the exchange of information in distributed computing environments. SOAP consists of three components: an envelope, a set of encoding rules, and a convention for representing remote procedure calls. Unless experience with SOAP is a direct requirement for the open position, knowing the specifics of the protocol, or how it can be used in conjunction with HTTP, is not as important as identifying it as a natural application of XML.

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What is DOM and how does it relate to XML?

The Document Object Model (DOM) is an interface specification maintained by the W3C DOM Workgroup that defines an application independent mechanism to access, parse, or update XML data. In simple terms it is a hierarchical model that allows developers to manipulate XML documents easily Any developer that has worked extensively with XML should be able to discuss the concept and use of DOM objects freely. Additionally, it is not unreasonable to expect advanced candidates to thoroughly understand its internal workings and be able to explain how DOM differs from an event-based interface like SAX.

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the differences between XML and HTML?

XML
User definable tags
Content driven
End tags required for well formed documents
Quotes required around attributes values
Slash required in empty tags

HTML
Defined set of tags designed for web display
Format driven
End tags not required
Quotes not required
Slash not required.


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