Wednesday, July 30, 2008

Run-time system

In computer science, the runtime system is software that provides services for a running program but is itself not considered to be part of the operating system.[citation needed]

Examples include:

* the code that is generated by the compiler to manage the runtime stack.

* library code for handling memory management (for example, malloc).

* code that handles dynamic loading and linking.

* debugger code that is generated at compile time or run time.

* application-level thread management code.

Byte-code interpreters and virtual machines can also be considered runtime systems. Services that run in concurrent processes are more likely to be considered middleware.

Wednesday, July 23, 2008


In some cases, two transactions may, in the course of their processing, attempt to access the same portion of a database at the same time, in a way that prevents them from proceeding. For example, transaction A may access portion X of the database, and transaction B may access portion Y of the database. If, at that point, transaction A then tries to access portion Y of the database while transaction B tries to access portion X, a deadlock occurs, and neither transaction can move forward. Transaction-processing systems are designed to detect these deadlocks when they occur. Typically both transactions will be cancelled and rolled back, and then they will be started again in a different order, automatically, so that the deadlock doesn't occur again. Or sometimes, just one of the deadlocked transactions will be cancelled, rolled back, and automatically re-started after a short delay.

Deadlocks can also occur between three or more transactions. The more transactions involved, the more difficult they are to detect, to the point that transaction processing systems find there is a practical limit to the deadlocks they can detect.

Wednesday, July 16, 2008

Data quality

1. Data Quality refers to the degree of excellence exhibited by the data in relation to the portrayal of the actual phenomena. GIS Glossary

2. The state of completeness, validity, consistency, timeliness and accuracy that makes data appropriate for a specific use. Government of British Columbia

3. The totality of features and characteristics of data that bears on their ability to satisfy a given purpose; the sum of the degrees of excellence for factors related to data

Thursday, July 10, 2008

Object-relational database

An object-relational database (ORD) or object-relational database management system (ORDBMS) is a database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language. In addition, it supports extension of the data model with custom data-types and methods.

One aim for this type of system is to bridge the gap between conceptual data modeling techniques such as Entity-relationship diagram (ERD) and object-relational mapping (ORM), which often use classes and inheritance, and relational databases, which do not directly support them.

Another, related, aim is to bridge the gap between relational databases and the object-oriented modeling techniques used in programming languages such as Java (programming language), C++ or C#. However, a more popular alternative for achieving such a bridge is to use a standard relational database systems with some form of ORM software.

Wednesday, July 02, 2008

Types of spam

Spam has several definitions, varying by the source.

* Unsolicited bulk e-mail (UBE)—unsolicited e-mail, sent in large quantities.
* Unsolicited commercial e-mail (UCE)—this more restrictive definition is used by regulators whose mandate is to regulate commerce, such as the U.S. Federal Trade Commission.
* Any email message that is fraudulent.
* Any email message where the sender’s identity is forged, or messages sent though unprotected SMTP servers, unauthorized proxies, or botnets