Tuesday, 29 July 2014

Database Languages

A database system provide Data Definition Language(DDL) to specify Database schema and Data Manipulation Language(DML) to express Database queries and updates. They are a part of a single Database language, such as the widely used SQL language.

Data Manipulation Language (DML)

DML allows users to acces and manipulate data as organized by the appropriate

data models.The types of access are,

* Retrieval of data

* Insertion of data

* Deletion of data

* Modification of data

Basically there are two types of DMLs,

1) Procedural DML

Here user need to specify what data and how to access that data

2) Declarative DML (Non procedural DML)

Here user need to specify what the data is and the DML will find an effective way to access those data

Therefore users mostly prefer Declarative DMLs since it is easier to learn and it can efficiently carry out data access.

Data Definition Language (DDL)

We specify database schema by a set of definitions and additional properties of data using DDL. We specify the storage structure and access methods used by Database system by a set of statements in a special type of DDL called data storage and definition language.

The DDL provides facilities to specify certain consistency constraints. Database system implement integrity constraints that can be tested with minimal overhead.

* Domain Constraints

Declaring an attribute like int, char as a specific domain acts as constraints on the values it can take. They are checked whenever new data items are entered.

* Referential integrity

There occurs some cases where we want a value appearingin one relation must appear in another relation. In some cases database modification cause violation in Referential integrity. When that happens, the action that causes the violation is rejected.

* Assertion

Assertion is any condition that a database must always satisfy. Domain constraints and Refrential integrity are other forms of assertions. When an assertion is created, system tests for its validity. If it is valid, database allows further modification if it does not cause any violation.

* Authorization

Users are differentiated according to type of access that they have to the database. This differentiation among the users are expressed in terms of Authorization.

The different types of authorizations are,

  • Read authorization
  • Insert authorization
  • Update authorization
  • Delete authorization

Data dictionary is a special type of table that can be accessed and updated by the database system itself. The database system consults the data dictionary before reading and modifying the data.

Friday, 4 July 2014

Web Syndication

Common Web feed icon
    First of all, what is Syndication? Basically syndication is the supply of material for reuse and integration with other material, often through a paid service subscription. The best example of web syndication is Newspaper. News agencies distribute contents to newspapers, they reformat it and integrate it with other copies and publish it.
    Web syndication refers to the websites providing information and the websites displaying it. ie, A section of a website is made available for other websites to use. For the providing sites, it is an exposure across numerous online platform. For the receiving sites, it is an effective way of adding depths to their sites and making it more attractive. Online content syndication is a rapid growing industrial sector in both hardware and software field. In the early days, syndication was a heavy manual process. Then an agreement reached favouring both supplier and customers reached. According to the agreement the customers would simply copy the desired content from the supplier's Web site and paste it into their own. Thus it became an easy process.
    In order to implement this new communication process, a series of XML files are defined. There is no standard format for Web syndication. To use this technology, site owners create or obtain specialized software (such as a content management system) which, in the machine-readable XML format, presents new articles in a list, giving a line or two of each article and a link to the full article or post. Web logs and news websites are common sources for web feeds, but feeds are also used to deliver structured information ranging from weather data to "top ten" lists of hit tunes. The term syndication is used to describe making available a feed for an information source. Like syndicated print newspaper features or broadcast programs, webfeed contents may be shared and republished by other web sites.

Tuesday, 1 July 2014

A Movie Review


Thira is 2013 released movie directed by Vineeth Sreenivasan. It casts Dhyan Sreenivasan, Shobhana- the cenral character. The movie deals with human trafficking. This movie is an eye-opener against such crimes taking place in different parts of the country.

The film makes the debut of Vineeth Sreenivasan’s young brother Dhyan Sreenivasan and the return of actress Shobhana to Malayalam cinema after almost a decade. Vineeth Sreenivasan was inspired by the life of Sunitha Krishnan an Indian activist and founder of ‘Prajwal’ an institution that assist trafficked women and girls in finding the shelter.
Movie begins with the introduction of a cardiologist, Rohini Pranab (Shobhana), who apart from her job of a doctor also runs an organization for women which acts against women trafficking and helps orphaned girls. Things get into trouble when some girls from the organization get kidnapped.
Rohini sets out on a mission to find those who are behind her husband's murder and who have trafficked the girls. On the same path, we are introduced to Naveen (Dhyan Sreenivasan), who is in search of his kidnapped sister. Naveen and Rohini meet by chance and come to know that they have the same goal. Rest of the movie focuses on their mission to find the lost ones. The story is set in Kerala and Goa. Both of them finally identify the secret place where the trafficked girls are kept and release with the wise help from Rohini and action from Naveen.
Thira merely reminds us that even those with eyes, see only that which they want to see through the scene of girl being kidnapped in the middle of the city in a day.
The main issue with stories of these kinds is that they have a predictable pattern with real events happening only at the beginning and then towards the end. What keeps the viewers glued on to such films are the portions that connect these two ends. Rakesh Mantodi's script (co-written by Vineeth Sreenivasan) barely manages to make things interesting and gripping beyond a point. Also, the dialogues have been written in an old fashioned style.

. 'Thira' does require an actress of great caliber, and Shobhana delivers an incredible performance and Dhyan Sreenivasan makes a notable debut as well, though he does need to work on his dubbing skills.