Internet Software Architecture

 

XML (Extensible Markup Language)

• It is much like HTML but more strict.
• It is used to describe data in a standard way, enabling it use in many situations.
• XML is self describing.
• It uses the document type definition to formally describe the document in terms of its format and the standards it follows.

 

XML Format

• Every XML document has a document type defintion at the top
• Every XML document Consists of a single root element
• An element can have many attributes
• An element can contain character data
• Every open element must have a close
• Everything in an XML document must be in lower case apart from the data

 

Differences Between XML and HTML

• XML has no predefined elements, HTML has.
• HTML was specifically designed for the World Wide Web
• The goal of HTML is to display data
• The goal of XML is to describe data

 

How PHP Supports XML

• PHP has a number of functions to parse and create XML documents
  • Parsing XML
    • xml_parser_create();
    • xml_parser_free();
    • xml_parse();
    • xml_set_element_handler();
    • xml_set_character_data_handler ();
  • Creating
    • DomDocument();
    • createElement();
    • appendChild();
    • setAttribute();
    • CreateTextNode();
    • saveXML();

 

 

Software Agents

Definition

A software agent is a small complex program that works toward goals instead of individual tasks in an ever changing environment. It works on behalf of an entity, human or computational. The software agent works without direct supervision or control from an external entity.

 

Software Agent Properties

• Small
• Autonomous
• Adaptive
• Mobile
• Persistent
• Collaborative
• Flexable
• Proactive

 

Software Agents Need

• A starting point for finding resources
  • The software agent uses the Agent Name Server (ANS) for this purpose
• A language enabling an agent to collaborate with other agents
  • ACL (Agent Communication Language)
  • or KQML (Knowledge Query and Manipulation Language)

 

Mobile Agent

A mobile agent is a software agent that moves from host to host within a network rather than staying in a fixed location. The following concerns are apparent when looking into mobile agents:

• Security
  • How to decide what to accept
  • How much independence to give agent eg routing
• Authority
  • Who owns the agent?
• Legality
  • Who is responsible for the agent’s actions
• Ethics
  • Who decides the context of use?

 

Distributed Agents

Distributed agents are a collection of software agents with comman goals. CISCO uses this technology for security to:

• Monitor patterns, behaviours
• Monitor themselves
• Communicate with other agents
• Monitor other agents

 

 

PHP Vs ASP.net

 

Accessibility

Perceivable

• Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
• Provide alternatives for time-based media.
• Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
• Make it easier for users to see and hear content including separating foreground from background.

Operable

• Make all functionality available from a keyboard.
• Provide users enough time to read and use content.
• Do not design content in a way that is known to cause seizures.
• Provide ways to help users navigate, find content, and determine where they are.

Understandable

• Make text content readable and understandable.
• Make Web pages appear and operate in predictable ways.
• Help users avoid and correct mistakes.

Robust

• Maximize compatibility with current and future user agents, including assistive technologies.