XML: The last word

In the previous session, we saw what an Entity is. Now let us see what an

entity declaration is.

Entity declaration



Entity declarations are used to associate a name with some other fragment of

content. The content can be regular text, or of the document type declaration,

or a reference to an external file containing either text or binary data. There

are three types of entity declarations. They are:

External entity



External entities affiliate a name with the content of another file. External
entities allow an XML document to refer to the contents of another file. They

contain either text or binary data. If they contain text, the content of the

external file is inserted at the point of reference and parsed as part of the

referring document. Binary data is not parsed and may only be referenced in an

attribute as it is used to reference figures and other non-XML content in the

document. For example:

"/movies/subsidy.xml">

Using the term "&entertainment" in the document you can insert

the contents of the file /movies/subsidy.xml at the location of the entity

reference.

Internal entity



Internal entities associate a name with a string of literal text. The

advantage of this entity is that it allows you to define shortcuts for

frequently typed text or text that is expected to change, such as the revision

status of a document. Let us see this with an example:

CBL

"CyberIndia, Ltd.">

You can insert "CyberIndia, Ltd." anywhere in the text using &CBL

There are several entity references built into XML:

• &

An ampersand inside text would confuse the XML processor, so if you have text

such as "Barnes & Noble" you must substitute the "&"

with its entity reference: &

• <

The entity reference for the less than bracket, "<" is the same

as in HTML code. Use this inside attribute values.

• >

This reference entity produces the right angle bracket, >

• '

This is the entity reference for the single quote ( ' ). Use it inside

attribute values quoted with a single quote.

• "

This is the entity reference for the double quote ( " ).

Parameter entity



Parameter entities can only occur in the document type declaration.

Placing % (per cent-space) in front of its name in the declaration identifies a

parameter entity declaration. They are not recognized in the body of the

document. Parameter entities are used when elements have the same literal string

and are semantically same. This allows you to change the content model in only a

single place. For example, consider these two elements:

This content model can be defined using a parameter entity like:

Let us end this XML session with rudiments of a simple XML code where an

element "movies" is created with the element "Indian" under

it. I think you will understand better when you see the code.

three hours

Om puri

Good

In XML, the markup language shown above can have a DTD like this:

Continued...

In the .Net world, what happens to Microsoft’s COM and DCOM initiatives?

Is the distributed computing aspect of .Net en extension to COM? What happens to

those who are using competing distributive computing technologies such as CORBA?



COM/DCOM is the building block. They can be integrated in .Net. COM/DCOM will
not go away. We will continue to work on COM. On the Web server, we will

continue to work with components. DCOM, however, will be replaced with XML/SOAP.

There are still many business applications built around COM. SOAP and XML may

not be a good idea in a closed environment, here COM may be the answer.

Why should other companies accept XML and SOAP as standards?



Today, no two Web servers can communicate. This will become possible with XML
and SOAP. While XML has already been accepted as a standard, once people

understand the advantages of working with SOAP as it is platform independent,

this will also be adopted. It has already been accepted by IBM.

What is the status of Java in the .Net framework? C# looks a lot like

Java, have you incorporated anything from Java?



We have not taken anything from Java. One of the key points of .Net is that it
is language independent. Irrespective of the language you write your code in —

be it C, C#, Java Script, Visual Basic or for that matter even COBOL — you get

a pseudo machine code called intermediate language, which is executed on the

.Net framework. The same code can run on multiple devices–PCs, pocket PCs,

phones etc. There is no (specific) runtime (for the codes). You can also have

multiple executables running on a single process.

C# was created from C++ with some extra features, such as automatic garbage

collection.

When do you think the acceptance of .Net will be complete?



It is an evolution and would not be completed. Some of the .Net framework is
being accepted. It is not before 12-18 months that we will see major adoption of

the framework and products coming up.

From the Microsoft side, you will see Office.Net and the .Net version of

Windows 2000 being released during the end of 2001. Visual Studio is expected in

the second half of 2001. Parallel to this, you will see us supporting several

devices such as smartcards, in the .Net framework.