Quality of Service (QoS) for Web Services

Abstract

Web services are very important in the current world and facilitates a huge percentage of the data exchanges in the world. QoS is the overall performance of a web service as viewed or reviewed by the user of that particular service. The parameters that a user can use to estimate the QoS of a web service include: price, response time, availability, reliability, and modifiability. It is argued that web services are inadequate and are yet to answer questions that can ascertain the quality of service for the user and that a user cannot only depend on the expected functionality requirement to tell the QoS of a web service. A new registry was proposed that aims to enhance communication between the user and service provider thus improving the service provision to satisfy the user’s needs. Though the proposal offers a good idea, the process of Quality of Service evaluation and decision making still wholly falls on the user. Web services keep integrating and getting better each day and therefore the QoS is subject to change. It is recommended that Service Providers should seek to provide the best Quality of Service at a minimal and reasonable cost to be able to cater for a wider range of users. Service providers must seek always to satisfy the user’s requirements above everything since it is the users that keep them in business. The users should do research and find out the QoS provided by a web service before registering and also stay in communication with the service providers through reviews so as to initiate the modification of the services. Users should embrace web services in totality and aim to get educated on how they can make the most from the web.

Introduction

Technology has substantially revolutionized the world in terms of governance, business, social interactions, and economy. Social media, e-commerce, and information systems are some of technologies spearheading the change being witnessed. The denominator in all these technologies is their reliance on web services, which refers to data transfer or data exchange system that is reachable through a standard web protocol. By nature, web services use the internet to transfer data from one application to another. A key tool in the measurement of functionality of a Web Service is the Quality of Service. QoS is the overall performance of a service as viewed or reviewed by the user of that particular service (Duwaldt 2002). It is a set of non-functional attributes that may affect the kind of service provided by a web service (Ran, 2003). The parameters used to measure the QoS of a web Service are: The cost of the web service, response time, accessibility or availability, reliability, security, user friendliness and the reputation of the web service (Hwang et al., 2007). Therefore, the ability of incorporating QoS into service discovery is very important.

Web Services.
Definition

Web services have been defined differently by different authors. Key words in the definition that crop out is the communication happening between two or more devices over the network. There is a collection of standards between the machines communicating. In the world of technology, web services are mainly known to fall under two categories and these are, SOAP and RESTful web services. The former, SOAP, stands for Simple Object Access Protocol. These web services in this category are known to be XML- based. The communication between two applications using SOAP get recommendation for W3C. When a web service is said to be using SOAP, it simply means that there is independence of platform and programming language that is or are being used in making the service run.

On the other hand, RESTful web services is known to be built exclusively on the architecture of REST. It is not heavy in the way it is built and therefore making it maintainable and scalable.

Standards

Web services standards are the procedures set to act as the glue sticking computers together as they interact. They form a whole and a greater computing environment which is accessible from any other device that is on the network.

Protocols

By definition in the field of technology, protocol is the rules or procedures set in order to make the process of data transfer easy and flawless between electronic devices. There are several of them which include: Open Systems Interconnection or rather OSI which is a set of guidelines implementing networking communication between or among computers. There are other major protocols. WSDL ( Web Services Description Language) is one of them. It is a document of xml where information about a web services is stored (Bidgoli, 2006). In operation, it is the interface upon which web services take place. Also, UDDI (Universal Description, Discovery and Integration). It is also XML based having a describing, discovering and integrating framework for web services. It is a directory of services in the websites.

Quality of Service

Technologies set together working on a network guaranteeing the ability to dependably run high priority set of applications as well as traffic under a limitation brought by a network capacity is called Quality of Service. It is therefore rendered vital to real-time traffic such as voice over IP, video-on-demand having a high sensitivity to jitter and latency and high bandwidth.

Objective

To build the knowledge about Web Services and to gain an understanding of the Quality of Service (QoS) provided by Web Services.

Literature Review

Studies on web services have been conducted over the years and various theories on the same have emerged. Most of these studies seek to understand and create a solution to the problems users experience when using web services. This is evident in Shuping Ran’s web service model in which poor quality of service is a major factor contributing to the slow take-up of web services technology. Shupin argues that web services are inadequate and that they are yet to address questions, such as how a user can ascertain the QoS of a service. A user cannot depend on the anticipated functional requirements to tell the QoS of a service (Ran, 2003). Owing to the limitations suggested by Ran (2003), the study proposed new registry different from the current universal description, discovery, and integration (UDDI) model. The proposed new registry was to contain all the data revolving around the functional description of the service and its QoS registered in the repository.

While Ran’s (2003) proposal improves the determination of the QoS, it also lengthens the process of registering into a web service. This process can be simplified into a transfer process or exchange between the service provider and the user whereby, the web service provider sends its QoS claim to the user, the user then checks to verify the veracity of the claims and either concurs with it or critiques it and then sends the feedback back to the service provider. Although the proposal is objective and it seeks to improve the QoS of a web service, the QoS is still not guaranteed as it can only be actually verified as good or satisfactory after the web service has been used and the user has evaluated its parameters. The web service provider also benefits from this new proposal since they receive feedback from the user and can always improve their services depending on the reviews from the user to cater for the needs of those users.

Based on Ran’s (2003) observations and recommendations, QoS therefore rests upon both the service provider and the user. The Service provider is to provide the user with web service offers with QoS aspects and the user is required to define their requirements in a particular service thus their needs are catered for in the service (Jiang et al. 2009). This means that web services are subject to change since the service provider is under obligation to cater for the clients’ preferences. Thus the web services have to undergo regular updating processes where new functionalities are introduced and the existing ones revised or updated as per the users requirements. To keep the system up to date as dictated by the user requirements, the registries should be checked regularly for new offers and the service updated to meet the standards of the user. Consequently, the Integration of QoS of Web Services is a continuous process that is progressive and will continue even in the years to come.

Internet of Things (IoT)

IoT refers to the many physical devices that are around the universe and are connected to the internet. They in one way or the other collect and share data. The way a device is added to this category is when a sensor and intelligence to it. The idea to do this is in recent history of 1980s and 1990s (Xia et al., 2012). Though there was progress during this time, it was slow and expensive. This was made so by the fact that chips were bulky and too big.

Later, new technologies came into existence and made it possible to ease the cost of production of chips while maintaining the quality, improving the efficiency and adjusting its energy consumption. This was made possible by the RFID tags adoption and the improvement of speed and broadband internet connectivity. Now, small but effective chips are all over the world in billions.

Parameters Used in QoS Evaluation

Response Time

Response time refers to the maximum time taken in the execution of a service or task in a web service. This parameter can be used as a measure of speed of a web service in the response of a service request. Web services with good QoS should have a short response time with minimal delays and can run a number of service requests simultaneously with minimal average delay (Thirumaran et al. 2010). Hence, when a web service has short response time it can be described to have good QoS.

Availability

As a parameter, availability is the reachability or accessibility of a web service. For a Web Service to have a good QoS, it should be readily available and accessible for the users. The user should be able to access or reach this service with minimal or no effort at all and at any time they want. Web services with poor accessibility discourage users since, such a service can cause delay in service requests and subsequently disorganizing the user with regard to the task that the web service is to perform. Availability cannot be measured as a physical quantity, but it can be estimated using time (Gunther 1998). When measured mathematically, it is a simple percentage calculated by dividing uptime by the total time span. For instance, a web service with a one hour downtime during the whole year 99.99% availability.

Reliability

Reliability is the probability in which a service provides a correct answer to a request within the response time. Web service with good QoS must be reliable. Reliability just like availability cannot be measured as a physical quantity but can be estimated as a function of successful requests where,

User Friendliness

User friendliness is the ease of use of a web service as a result of an interface that is easy to understand. It is an important factor as it dictates whether users will opt for a particular service or not. When a web service is not user friendly, it is difficult to understand and operate and thus subjecting the user to learn how to navigate the system first then be able to use it after that. This is a waste of time and most users are irritable by this thus they opt for other options or web services that are less tedious to use.

Modifiability

This is the ability of a web service to be modified or updated to improve on the service delivery in general or add new functionalities for the betterment of the service. For a web service to cater for a user’s needs on a long-term basis, then is has to be modifiable. This gives room to add or change a functionality in the service to the preference of the user. This also allows the service provider to do away with a service that has become obsolete. Non-modifiable services are therefore slowly becoming outdated since the user preferences and requirements are subject to change. It is therefore advisable for a user to opt for a modifiable web service. It is also important to note that the web service can only be modified by the service provider and not the user.

Security

This is the safety of a user’s data while transferring it through a web service or while it is stored in a web service. Security of information on web services is ensured and enhanced by a variety of high-tech protocols put in place to safeguard the integrity of the web services. Services with poor or inadequate security mechanisms have been exposed to hacking and other malicious practices that have eventually jeopardized the safety of the user’s data (Menasce, 2002). In some cases, clients have lost their information and sometimes even money. Organizations and people can lose important information and in the event that this information lands in the wrong hands then they would face dire consequences. High security protocols must also be put in place in the authentication of principals during the access of their services especially in the transaction services. The system put in place to verify the identity of their users should be very accurate so as not to leave room for fraudsters to manipulate their way into the web services. The authorization of principals to a particular service should have a particular threshold whereby only upto three people from an organization can be allowed to access a service and they should be registered as the administrators and so therefore anyone who is not an administrator cannot have access to the same.

When all the protocols put in place to observe security are fully functional, then the web service should be accountable for the safety of their clients’ information (Yu & Lin, 2014). However, this is not the case for most web services. Another area of concern is the data encryption technique that a web service uses. The technique used to encrypt data should be very strong and difficult to decrypt so that in the event that the service is hacked and data is lost then the perpetrators that stole the data would find it difficult if not impossible to decrypt the data. Thus it is recommended that in the evaluation of QoS of a web service, a user should carefully consider the security of a web service as a key factor in the selection of a good web service.

Cost of the Web Service

This parameter refers to the expenses incurred by a user in the registration in the registration and use of a web service over a period of time. It is the desire of most web services users to incur minimal losses and save as much as possible. However, this is not the case as the price of a web service is directly correlated to the quality of the service. For one to enjoy good quality web service then they must be willing to pay the price. Therefore, a web service that charges highly for its operations is considered a better service than the one with discounted charges. So whenever a user is charged highly, it should be accompanied with excellent web services to their satisfaction. If that is not the case, then the user should consider finding a better service provider. Web service providers should also be considerate in their costs to cater for people on different social levels. A good way of ensuring that is by providing a wide range of services that have different costs depending on their functionalities (Tsalgatidou et al.  2008). That way, a user chooses a service package that they can afford.

Integrity

Integrity is the principles and honesty of a web service provider in their services and transactions with the users. Integrity and honesty are key in web services as users have no option but to trust service providers with their data and money. Integrity is the foundation to being the best service provider. Without integrity, quality of service cannot be guaranteed to the users and therefore, the service provider may lose clients eventually. Integrity especially in transactional web services is important and can either build or break the web services (Sara 2014). Being that transactional web service providers have users’ information and are able to access the system from within then their integrity is what holds their clients. Service providers that lack integrity end up stealing from their clients or doctoring data to benefit them and at the end of the day, they become the very fraudsters that that take part in malicious practices on web services. Thus it is very important for service providers to exercise integrity and honesty in all their dealings with clients.

Conclusion and Future Work

Web Services have been there for years and they keep getting better and better, this is mainly dependent on the fact that the use of web services has increased tremendously and the human race has become somewhat dependent on web services. Web services have made life and communication very easy and it has also expanded the job market. People have jobs building, managing and selling web services (Rajendran et al., 2010). Businesses have been built on web services e.g the online businesses or websites where one can access stores online such as Amazon. The integration of web services is as a result of the fast growing technology in the world. This is to say that as long as technology keeps getting better and better, web services are there to stay.

Since web services keep increasing and integrating, then the quality of services provided should also meet the user requirements. In as much as the web service provider is under obligation to provide quality services, the user must also be on the lookout for the best services. Therefore, before registering to particular web service, a user is supposed to evaluate the QoS of the service (Davies et al. 2004). It is also important though not mandatory for a user to give honest reviews on the QoS of a service for the modification of the service so that it meets the user standards. The factors a user can use to determine the QoS of a service include: Response time, Availability, Reliability, Modifiability, Security, Price, Integrity etc.

Recommendations

The first recommendation is that service providers should seek to provide the best QoS at a minimal and reasonable cost to be able to cater for a wider range of users. Service providers must seek always to satisfy the user’s requirements above everything since it is the users that keep them in business. The users should do research and find out the QoS provided by a web service before registering and also stay in communication with the service providers through reviews so as to initiate the modification of the services. Users should embrace web services in totality and aim to get educated on how they can make the most from the web.