29-05-2015, 02:49 PM
Abstract of Extended Markup Language
Many Web pages today are poorly written. Syntactically incorrect HTML code may work in most browsers even if it doesn't follow HTML rules. Browsers employ heuristics to deal with these flawed Web pages; however, Web-enabled wireless devices (such as PDAs) can't accommodate these hefty Web browsers. The next step in HTML's evolution comes in the form of XHTML (eXtended Hypertext Markup Language), which is basically a combination of HTML and XML.
XML, the eXtended Markup Language, is a successor for SGML. More general than html, it incorporate data inside tags themselves and has unlimited description capacities. The format of the display is independant, and given by another document, the XSLT. Rules to create tags are defined by another document, the DTD (Document Type Declaration) which describes the grammar of the tags.
Xml features
- Significant tags based upon the content of data.
- Separated document used for the presentation.
Why to use Xml?
This is a standard and universal data format. It allows to reuse a presentation for different data or use different presentations for same data.
As business and enterprises generate and exchange XML data more often, there is an increasing need for efficient processing of queries on XML data. Searching for the occurrences of a tree pattern query in an XML database is a core operation in XML query processing. Prior works demonstrate that holistic twig pattern matching algorithm is an efficient technique to answer an XML tree pattern with parent-child (P-C) and ancestor-descendant (A-D) relationships, as it can effectively control the size of intermediate results during query processing. However, XML query languages (e.g. XPath, XQuery) define more axes and functions such as negation function, order-based axis and wildcards.Here we research a large set of XML tree pattern, called extended XML tree pattern , which may include P-C, A-D relationships, negation functions, wildcards and order restriction. We establish a theoretical framework about " matching cross " which demonstrates the intrinsic reason in the proof of optimality on holistic algorithms. Based on our theorems, we propose a set of novel algorithms to efficiently process three categories of extended XML tree patterns. A set of experimental results on both real-life and synthetic data sets demonstrate the effectiveness and efficiency of our proposed theories and algorithms.
How does it all work?
To understand how this all works, we need to start with the basics. Encryption has been around for centuries, Julius Caesar used encrypted notes to communicate with Rome thousands of years ago. This traditional cryptography is based on the sender and receiver of a message knowing and using the same secret key: the sender uses the secret key to
encrypt the message, and the receiver uses the same secret key to decrypt the message. 21 years ago, a revolution happened in cryptography that changed all this, public-key cryptography. In 1976, Whitfield Diffie and Martin Hellman, introduced this new method of encryption and key management. A public-key cryptosystem is a cryptographic system that uses a pair of unique keys (a public key and a private key). Each individual is assigned a pair of these keys to encrypt and decrypt information. A message encrypted by one of these keys can only be decrypted by the other key in the pair.
The public key is available to others for use when encrypting information that will be sent to an individual. The private key is accessible only to the individual. The individual can use the private key to decrypt any messages encrypted with the public key. Similarly, the individual can use the private key to encrypt messages, so that the messages can only be decrypted with the corresponding public key.
Several bodies are actively involved in examining the issues and in developing standards. The main relevant developments here are XML encryption and the related XML signature, eXtensible Access Control Language (XACL), and the related Security.