What are the parameters of QoS - Quality of Service?

With the arrival of the new technologies, applications and services in the field of networking, the competition is rising rapidly. Each of these technologies, services and applications are developed with an aim of delivering QoS (quality of service) that is either better with the legacy equipment or better than that. The network operators and the service providers follow from trusted brands. Maintenance of these brands is of critical importance to the business of these providers and operators. The biggest challenge here is to put the technology to work in such a way that all the expectations of the customers for the availability, reliability and quality are met and at the same time the flexibility for quick adaptation of the new techniques is offered to the network operators. 

What is Quality of Service?

- The quality of service is defined by its certain parameters which play a key role in the acceptance of the new technologies. 

- The organization working on several specifications of QoS is ETSI.

- The organization has been actively participating in the organization of the inter-operability events regarding the speech quality.

- The importance of the QoS parameters has been increasing ever since the increasing inter-connectivity of the networks and interaction between many service providers and network operators for delivering communication services.

- It is the quality of service that grants you the ability for the making parameters specifications based up on multiple queues in order to shoot up the performance as well as the throughput of wireless traffic as in VoIP (voice over internet), streaming media including audio and video of different types. 

- This is also done for usual IP over the access points.

- Configuration of the quality of service on these access points involves setting many parameters on the queues that are already there for various types of wireless traffic. 

- The minimum as well as the maximum wait times are also specified for the transmission. 

- This is done through the contention windows. 

- The flow of the traffic between the access point and the client station is affected by the EDCA (AP enhanced distributed channel access) parameters. 

- The traffic flow from client to the access point is controlled by the station enhanced distribution channel access parameters. 

Below we mention some parameters:

Ø  QoS preset: The options listed by the QoS are WFA defaults, optimized for voice, custom and WFA defaults.

Ø  Queue: For different types of data transmissions between AP – to – client station, different queues are defined:

- Voice (data 0): Queue with minimum delay and high priority. Data which is time sensitive such as the streaming media and the VoIP are automatically put in this queue.

- Video (data 1): Queue with minimum delay and high priority. Video data which is time sensitive is put in to this queue automatically.

- Best effort (data 2): Queue with medium delay and throughput and medium priority. This queue holds all the traditional IP data. 

- Background (data 3): Queue with high throughput and lowest priority. Data which is bulky, requires high throughput and is not time sensitive such as the FTP data is queued up here.

Ø AIFS (inter-frame space): This puts a limit on the waiting time of the data frames. The measurement of this time is taken in terms of the slots. The valid values lie in the range of 1 to 255.

Ø Minimum contention window (cwMin): This QoS parameter is supplied as input to the algorithm for determining the random back off wait time for re-transmission.

Ø cwMax

Ø maximum burst

Ø wi – fi multimedia

Ø TXOP limit

Ø Bandwidth

Ø Variation in delay

Ø Synchronization

Ø Cell error ratio

Ø Cell loss ratio

What are autonomic systems? What is the basic concept behind autonomic system?

In this article we shall discuss about the autonomic systems, but before moving on to that we shall see a brief discussion regarding the autonomic computing. 

About Autonomic Computing

- Distributed computing resources have the ability of self–management. 

- This kind of computing is called autonomic computing and such systems are called autonomic systems. 

- Because of their unique capabilities, these systems are able to adapt to the changes that are both predictable and unpredictable. 

- At the same time, these systems keep the intrinsic complexities hidden from the users as well as the operators. 

- The concept of autonomic computing was initiated by IBM in the year of 2001. - This was started in order to keep a curb on the growing complexity of the management of the computer systems and also to remove any complexity barriers that prove to be a hindrance in development.

About Autonomic Systems

- Autonomic systems have the power to make decisions of their own. 

- They do this because of the high level policies. 

- These systems automatically check and optimize their status and adapt to the conditions that have changed. 

- The frame work of these computing systems is constituted of various autonomic components that are continuously interacting with each other. 

- Following are used to model an autonomic component:

1. 2 main control loops namely the global and the local.
2. Sensors (required self – monitoring)
3. Effectors (required for self-adjustment)
4. Knowledge
5. Adapter or planner

- The number of computing devices is increasing by a great margin every year. - Not only this, each device’s complexity is also increasing. 

- At present highly skilled humans are responsible for managing such huge volume of complexity. 

- The problem here is that the number of such skilled personnel is not much and this has led to a rise in the labor costs.

- It is true that the speed and automation of the computing systems have revolutionized the way world runs but now there is a need for a system that is capable of maintaining these systems without any human intervention. 

- Complexity is a major problem of the today’s distributed computing systems particularly concerning their management. 

- Large scale computer networks are employed by the organizations and institutions for their computation and communication purposes. 

- These systems run diverse distributed applications that are capable of dealing with a number of tasks. 

- These networks are being pervaded by the growing mobile computing. 

- This means that the employees have to be contact with their organizations outside office through devices such as PDAs, mobile phones and laptops that connect through wireless technologies. 

- All these things add to the complexity of the overall network that cannot be managed by human operators alone. 

- There are 3 main disadvantages of manual operating:

1. Consumes more time
2. Expensive
3. Prone to errors

- Autonomic systems are a solution to such problems since they are self – adjustable and do not require human intervention. 

- The inspiration or the concept behind the autonomic systems is the autonomic nervous system found in humans.

- This self – manageable system controls all the bodily functions unconsciously. - In autonomic systems, the human operator just has to specify the high level goals and rules and policies that would guide the management. 

- There are 4 functional areas of an autonomic system:

1. Self–configuration: Responsible for the automatic configuration of the network components.
2. Self–healing: Responsible for the automatic detection and correction of the errors.
3. Self–optimization: Monitors and controls the resources automatically.
4. Self–protection: Identifies the attacks and provides protection against them.

- Below mentioned are some characteristics of the autonomic systems:

1. Automatic
2. Adaptive
3. aware

What are different mutation testing methods?

Mutation testing is another methodology of software testing. It can be defined as the software testing methodology which involves modification of source code or programs or the byte code of the program in a way that is particularly small but significant.

Mutation is known by two other names:
- program mutation
- mutation analysis.

SOME IMPORTANT FACTS
- The mutated code is tested using various cases and the test suite that doesn’t detects and rejects the code that has been mutated is usually considered to be defective in nature.

- The required mutations are carried out on the basis of some well defined operators known as mutation operators.

- These mutation operators are well known to mimic typical programming bugs or errors and some times they also force the creation of tests which are significantly valuable tests.

- Best example of such test is given by the test which derives each expression to the value zero.

- The purpose of the mutation testing is basically to allow the tester or software developer to develop effective test cases so that the weaknesses or the vulnerabilities of the software system or application can be located or detected in the test data that is being used as the input for the program or in the sections of the program code.

- These sections are chosen as such that they are rarely used and accessed during the execution of the software system or the application.

- The mutation testing is carried out to ensure or verify that the implemented software program or application is correct or not.

Still the creation of the mutation testing poses some doubts.
- The doubt is whether the mutation tests are correct or not?
- Whether they sufficiently cover all the specifications and the requirements that have lead to the origination of the implementation of the test cases?

Mutation testing represents a technological problem of “who will guard the guards?”
- In the 19s, the mutation testing was pioneered to detect or locate the weaknesses and the potential vulnerabilities of the test suites.

- A theory was put forward regarding the behavior of the mutation testing.

- It stated that if a mutation was done without affecting the behavior of the program or output, then it meant that either the code that had been mutated did not execute or the employed testing suite wasn’t able to detect the injected mutation.

- In order to make one mutation work, one has to introduce many mutations all over the program.

- This in turn leads to the compilation of a large number of copies of the program code.

- The increase in the use of unit testing frame works and object oriented programming languages has led to the increase in the creation new mutation testing tools for other programming languages.

METHODS FOR MUTATION TESTING
- Mutation testing is carried out by selecting few mutation operators and then applying them to the source code using one at a time for each correct piece of the program code.

- The resultant of application of a mutation operator is known as mutant.

- If the mutant is detected during the testing, then the mutant is said to be killed.
- Strong mutation testing or strong mutation coverage ensures that the test suite is effective in detecting the mutants.
- Weak mutation coverage or weak mutation testing can be related to code coverage methods.
- It takes less number of calculations to ensure the effectiveness of the weak mutation testing.
- In some cases equivalent mutants are also used.
- In those cases it becomes impossible for a test suite to kill such a mutant.

- Equivalent mutation proves to be the greatest obstacle in the path of practical usage of the mutants.
- Equivalent mutants require more efforts for testing.
- A variety of mutation operators have been discovered by the researchers.

What is Assignment and Logical Comparison in C...

An expression as we all know is composed of one or more operations. When the expression is terminated by a semi colon, it becomes a statement which is the small executable unit in any program. The assignment statements are used to assign a value to a variable. The assigned value can be a constant variable or an expression. An assignment statement can be written in general form as:

A=bcd;

Where A is a variable to whom we are assigning a value and bcd is the assigned value. The “=” sign is called assignment operator. Assignments can be chained together. The assigning operator “=” assigns the value to the left hand operand and returns the value of the assignment. Assignment statements are very much needed for variable initialization since variables are initialized using assignment statements. There are 2 ways to do this:
- Un-initialized variable
- Initialized variable
An un-initialized variable has to be initialized in separate statements whereas an initialized variable combines declaration and assignment in to one statement.

Examples are:
Int a;
a=3; ------------------------uninitialized variable
int a= 3; -------------------- initialized variable

Assignment also follows when you use dynamic initialization. Sometimes variables of different types are mixed with each other. It’s a very common and observed phenomenon. In such cases a type conversion takes place. Here also it follows from the principal of assignment statement that “the value of the right side of the expression or of the assignment is converted to the type of the variable on left side i.e., target variable. Both the sides of assignment should be compatible with each other for type conversion. When conversion takes place from smaller data type to a larger data type no data is lost. Precedence of operators while assigning values with an expression should always be kept in mind.
Some programs need the power of decision making or comparison. This is granted through logical expressions which are nothing but the statements resulting into a 0 (true) or 1 (false) value. These are a combination of constants, variables and logical and relational operators. Be careful that two or more variables and operators should not occur in continuation. A logical expression may contain just one signed or unsigned variable or a constant or it may have two or more also joined by varied relational and logical operators. Following are some valid logical operators: the logical OR operator (||), the logical AND operator (&&) and the logical NOT (!) operator. The OR operator combines 2 expressions as its operands. If either of its operand evaluates to true, the OR operator also evaluates to true. This operator is basically used for testing evaluating expressions. The AND operator combines 2 expressions into one and the operator evaluates to one if and only if both the operands evaluate to 1. The NOT operator works on a single operand since it is a unary operator. It is used to negate or reverse the truth value of the operand. It has a higher precedence than of the relational and logical operators. Therefore, this should be enclosed within parentheses. This operator is useful as a test for zero. OR and AND operators have lower precedence than relational operators. Relational operators are used to define relationships between variables. C provides 6 basic relational operators : < (less than), > (greater than), <= (less than or equal to), >= (greater than or equal to), == (equal to), and != (not equal to). Do not confuse the = and the == operators. “=” is assignment operator whereas “==” is relational equality operator.

Mutation Testing : how it is performed, benefits, operators and tools.

Mutation Testing is a powerful method for finding errors in software programs. Mutation testing involves deliberately altering a program’s code, then re-running a suite of valid unit tests against the mutated program. A good unit test will detect the change in the program and fail accordingly. Mutation testing is expensive to run, especially on very large applications. Mutation Testing is complicated and time-consuming to perform without an automated tool.

How Mutation testing is performed?

- Create a mutant software which is different from the original software by one mutation.
- Each of the mutant software has one fault.
- Test cases are applied to the original software and the mutant software.
- Results are evaluated. The test case that is applied is wrong if the mutant software as well as the original software produces the same result. The test case is right if the test case detects fault in the software.

Benefits of Mutation Testing

- Introduces a new level of error detection.
- Uncover errors in code that were previously thought impossible to detect automatically.
- The customer will receive a more reliable and bug free software.

On what factors Mutation testing depends ?

- It depends heavily on the types of faults that the mutation operators are designed to represent.
- Mutation operators means certain aspects of the programming techniques, the slightest change in which may cause the program to function incorrectly.

Mutation Operators and Tools

Some mutation operators for languages like Java, C++ etc. are :
- Changing the access modifiers, like public to private etc.
- Static modifier change.
- Argument order change.
- Super keyword deletion.
- Essay writing services

Tools like Jester, Pester, Nester and Insure++ are some of the tools that are available for mutation testing.

Test Script Languages (TSL)

Test Script Language(TSL) is a scripting language with syntax similar to C language. TSL is the script language used by WinRunner for recording and executing scripts.

Features Of TSL :
- The TSL language is very compact containing only a small number of operators and keywords.
- TSL is a script language and as such, does not have many of the complex syntax
structures you may find in programming languages.
- On the other hand, TSL as a script language has considerably less features and capabilities than a programming language.
- Comments : Allows users to enter human readable information in the test script that will be ignored by the interpreter.
- Naming Rules : Rules for identifiers within TSL.
- Data Types : The different types of data values that are supported by the language.
- Data Storage : Constructs that can be used to store information.
- Operations : Different type of computational operations.
- Branching : Avoids executing certain portions of the code unless a condition is met.
- Loops : Repeats execution of a certain section of code.
- Functions : Group of statements used to perform some useful functionality.

There are four categories of TSL functions. Each category of functions is for performing specific tasks. These categories are as follows:
- Analog Functions
These functions are used when you record in Analog mode, a mode in which the exact coordinates of the GUI map are required. When you record in Analog mode, these functions are used to depict mouse clicks, keyboard input, and the exact coordinates traveled by the mouse. The various analog functions available are Bitmap Checkpoint Functions, Input Device Functions, Synchronization functions, Table Functions, Text Checkpoint Functions.
- Context Sensitive Functions
These functions are used where the exact coordinates are not required. In Context Sensitive mode, each time you record an operation on the application under test (AUT), a TSL statement is generated in the test script which describes the object selected and the action performed.
- Customization Functions
These functions allow the user to improve the testing tool by adding functions to the Function Generator. The various customization functions are custom record functions,
custom user interface functions, function generator functions and GUI checkpoint functions. Different context-sensitive functions are Active Bar Functions, ActiveX/Visual Basic Functions, Bitmap Checkpoint Functions, Button Object Functions
Calendar Functions,Database Functions, Data – driven test Functions,GUI related Functions etc.
- Standard Functions
These functions include all the basic elements of programming language like control flow statements, mathematical functions, string related functions etc. The various standard functions are arithmetic functions, array functions, call statements, compiled module functions, I/O functions, load testing functions, operating system functions, etc.

GIS Data Operations and Problems in GIS

GIS applications are conducted through the use of special operators such as the following :
- Interpolation : This process derives elevation data for points at which no samples have been taken. It includes computation at single points, computation for a rectangular grid or along a contour, and so forth.
- Interpretation : Digital terrain modeling involves the interpretation of operations on terrain data such as editing, smoothing, reducing details and enhancing. Additional operations involve patching or zipping the borders of the triangle and merging, which implies combining overlapping models and resolving conflicts among attribute data.
- Proximity analysis : Several classes of proximity analysis include computations of "zones of interest" around objects.
- Raster Image processing : This process can be divided into two categories (1) map algebra which is used to integrate geographic features on different map layers to produce new maps algebraically; and (2) digital image analysis, which deals with analysis of a digital image for features such as edge detection and object detection.
- Analysis of networks : Networks occur in GIS in many contexts that must be analyzed and may be subjected to segmentations, overlays, and so on.

PROBLEMS OF GIS :
GIS is an expanding application area of databases. As a result, number of problems related to GIS applications have been generated :
- New architectures : GIS applications will need a new client-server architecture that will benefit from existing advances in RDBMS and ODBMS technology.
- Versioning and object life-cycle approach : Because of constantly evolving geographical features, GIS must maintain elaborate cartographic and terrain data - a management problem that might be eased by incremental updating coupled with update authorization schemes for different levels of users.
- Data Standards : Formalization of data transfer standards is crucial for the success of GIS.
- Matching applications and data structures.
- Lack of semantics in data structures.