There are the basic rules for writing the XML:

• All XML should have a root element
• All tags should be closed
• XML tags are case sensitive
• All tags should be nested properly
• Tag names cannot contain spaces
• Attribute value should appear within quotes
• White space is preserved 

Data transferred over FTP is sent in ASCII, binary, EBCDIC or local modes. Most of the FTP clients automatically determine the data transfer mode based on the contents or extension of the file.

Audio, video and image files are generally transferred in binary mode, whereas HTML, script and text files are transferred in the ASCII mode.

Computers with identical setups transfer data in the local mode, and hosts using the EBCDIC character set use the EBCDIC mode for data transfer.

The most common use of FTP is to upload and download files, such as web page files, to a server. 

Websites use it in anonymous mode to power downloads. Some companies distribute their software 
updates using FTP.

FTP is not a secure protocol. FTP sends and receives all data in clear text and is, hence, vulnerable to packet capture or sniffing, port stealing, spoof attacks, bounce attacks, brute force attacks and user name hijacking.

FTPS, not to be confused with SFTP, is an extension of the standard FTP that allows the FTP clients to request an encrypted session. 

Cerberus FTP and Complete FTP is a couple of commercial FTP servers. FileZilla is an open-source freeware FTP server that also provides a free FTP client. Some of the other popular FTP clients are WinSCP, Transmit, FireFTP and Cyberduck.

FTP is a widely used method to transfer files over a network. FTP clients today have excellent graphical user interfaces. File transfers are seamless and just a matter of drag and drop.

XML is not replacement for HTML rather both were designed with different goals:

• XML was designed to describe data, with focus on what data is
• HTML was designed to display data, with focus on how data looks
• HTML is about displaying information, while XML is about carrying information.

XML is used in many aspects of web development, often to simplify data storage and sharing.

1. XML Separates Data from HTML
2. XML Simplifies Data Sharing
3. XML Simplifies Data Transport
4. XML Simplifies Platform Changes
5. XML Makes Your Data More Available on diverse applications
6. Internet Languages Written in XML: Several Internet languages are written in XML. Here are 
   some examples:
   • XHTML
   • XML Schema
   • SVG
   • WSDL
   • RSS

Simple elements may have a default value OR a fixed value specified. A default value is automatically 
assigned to the element when no other value is specified.

In the following example the default value is "red":

<xs:element name="color" type="xs:string" default="red"/>

A fixed value is also automatically assigned to the element, and you cannot specify another value.

In the following example the fixed value is "red":

<xs:element name="color" type="xs:string" fixed="red"/>

XPath is used to navigate through elements and attributes in an XML document. XPath is a major element in W3C's XSLT standard - and XQuery and XPointer are both built on XPath expressions.

• XPath is a syntax for defining parts of an XML document
• XPath uses path expressions to navigate in XML documents
• XPath contains a library of standard functions
• XPath is a major element in XSLT
• XPath is a W3C recommendation 

XQuery is a language for finding and extracting elements and attributes from XML documents. It is to XML what SQL is to database tables and is designed to query XML data.

• XQuery is the language for querying XML data
• XQuery for XML is like SQL for databases
• XQuery is built on XPath expressions
• XQuery is supported by all major databases
• XQuery is a W3C Recommendation since 2007.