WEB SERVICES - CURRENT TRENDS AND FUTURE OPPORTUNITIES
Narendran Calluru Rajasekar
November 19th, 2009
Supervised by
Elias Pimenidis
Mike Griffith
MSC Internet Systems Engineering
University of East London,
Docklands.
Table of Contents
3.5 QoS Attributes (Evaluation Criteria)
3.7 Web Services and Semantic Web
3.8 Web Services in Organisations
3.8.1 Enterprise Application Integration
4 Evaluating Web Services - Case Study
1 Abstract
This paper focuses on the current trends and future opportunities in each aspect of web services. Initially the requirements of web services are discussed and the QoS attributes which are the evaluation criteria for web services are defined. This paper also discusses on various standards and technologies involved in web service orchestration, monitoring and the role of web services in enterprise integration and communication. Later in this paper, a case study is presented on a website. The website uses web services provided by a web service provider which is evaluated based on the QoS attributes defined earlier in this paper.
Keywords: Web Services, Semantic Web, QoS Attributes, Amazon Web Service, Zoomii.
2 Introduction
Today, the cross enterprise business interaction is vital and needs to happen quickly without human intervention. The traditional work flow models are tightly coupled and requires dedicated network between companies for the interaction to happen. This involves high cost for the setup and reduces scalability and reusability (Papazoglou, M., 2003).
Web services are loosely coupled software components which enable interoperability between heterogeneous distributed components. They are available on Internet and are platform independent, thus allowing interaction between different applications (Cerami, E. and S. Laurent, 2002). Hence web services can be used for cross enterprise business interaction with the help of ubiquitous Internet.
3 Web Services
Cerami, E. and S. Laurent (2002) defines web service as
"any service that is available over the Internet, uses a standardized XML messaging system, and is not tied to any one operating system or programming language"
- Cerami, E. and S. Laurent (2002)
The web services are self-describing and discoverable. A series of standards such as WSDL, UDDI, SOAP, etc are used to support the activities of web services such as Description, Discovery and Invocation (Lau, R., 2007).
3.1 SOA with Web Services
Service Oriented Architecture (SOA) is a way of defining the communication model with which two different services can talk to each other regardless of the operating system, programming language and IT Infrastructure (Newcomer, E. and G. Lomow, 2005). Web service is a way of implementation of SOA where the components are loosely coupled and interoperable.
The components are loosely coupled and are accessible as individual components rather than as an application. Hence, they are more prone to security attacks (Jensen, M., N. Gruschka, et al., 2007). Also the non functional requirements such as security and integration are difficult since the ways of accessing the components are of wide variety. Yamany, H., M. Capretz, et al., (2009) has proposed metadata consisting of security paradigms and a Web Service is constructed for the consumer to access it.
3.2 Description
Web services are hosted in a server along with the description. WSDL (Web Service Description Language) is used to describe a web service. WSDL is an XML Grammar based standard accepted by W3C which provides communication level description of protocols and messages. At present keyword based approach is used widely to match description which can be inaccurate, Hu, J., P. Zou, et al. (2005) have proposed QoS based Web Service Description Language and a matching mechanism which is composed of QoS attributes and behaviour restraints and proved it to be efficient based on the experimental results.
Ankolekar, A., M. Burstein, et al. (2002) has provided web service descriptions at application level called DAML-S complementing to WSDL which makes the tasks such as invocation, interoperation, composition, verification, execution and monitoring much more easier with the semantic web.
3.3 Discovery
Web services are being developed everywhere and is available in the Internet, but finding a web service is what matters. UDDI Business Registry (UBR) is a collection of UDDI nodes or servers which consists of web service specification through which a web service can be discovered.
There is no single repository where all the web services are registered and hence finding a specific web service is difficult. Al-Masri, E. and Q. Mahmoud (2007) addressed the issue of searching web services by using an enhanced discovery model using Web Service Crawler Engine and have demonstrated with experimental results of achieving efficient search capabilities. Although there are some limitations such as access restriction to secure content, Al-Masri, E. and Q. Mahmoud (2008) says that "a crawler and a centralized repository for Web services is inevitable".
Discovering a web service is not the end of it! Discovering a web service which is of high quality is also necessary. Current techniques don't allow users to query based on the quality of a web service. For example, it is not possible for a user to select a web service whose response time is between some limits. This can be achieved by Web Service Broker which continuously collects the web services just like a search engine but in addition to it, evaluates it against various quality metrics and stores this information along with the web services (Al-Masri, E. and Q. Mahmoud, 2008). The additional information which the author calls as QWS dataset can be used for the quality driven web service discovery.
Figure 1 shows the classification of QoS parameter by Al-Masri, E. and Q. Mahmoud (2009) based on the quantitative measurements, client's perception and service provider's perception which can be used for discovery purpose.
Figure 1: Basic qualities of web service parameters (Source: Al-Masri, E. and Q. Mahmoud, 2009)
Kritikos, K. and D. Plexousakis (2009) Highlights an approach of selecting QoS based web services where mixed integer programming can be used to select appropriate web services which uses semantic based algorithm to match the description which will eventually increase the accuracy of the match.
3.4 Requirements
The requirement for web services changes according to various factors such as business needs, environments, reusability etc. Web services should be able to adapt or withstand these changes especially in high assurance systems. Hence web services should contain properties which will allow them to be reconfigured either statically or dynamically. Yen, I., H. Ma, et al. (2008) have proposed service transformation framework which allows the web services to be reconfigurable based on the rules defined on properties.
Service Level Agreements (SLA) which is also known as contracts is important for web service which is defined during requirements of a web service. Usually hard contracts like QoS value are some value within limits or predefined values. Soft contracts are something which considers time and the path of the flow as a factor and the thresh hold changes accordingly. The orchestration of a web service is very important to provide high quality service (Rosario, S., A. Benveniste, et al., 2008).
The composition web services i.e., the web services orchestrated by the composition of multiple web services are significant as this is the new way of developing solutions for business (Oh, S., D. Lee, et al., 2008). Thus the complex nature of business requirements sometimes requires dynamic selection of web services based on the environment and current inputs for the web service orchestration (Hwang, S., E. Lim, et al., 2008). The limitations are high in the failure prone environment, moving towards semantic web will help to overcome the limitations.
The dependability of web service can be improved by the mediator framework (Chen, Y. and A. Romanovsky, 2008). According to this framework, the web service mediators accept invocations from client and collect the information on resilience behaviour on web services, which can be used to improve dependability.
General techniques assume the environment and parameter to be static, but in reality this is not true and hence web service should adapt to the change automatically at runtime. This can be achieved by efficiently querying the changing parameters using the value of changed information during runtime (Harney, J. and P. Doshi, 2008). In order to achieve this, requirements should be defined considering all the above factors.
3.5 QoS Attributes (Evaluation Criteria)
QoS attributes of web services may vary for various domains and environment (mobile devices, streaming media, rich content, etc). For instance, the mobile devices requires specific factors for high QoS as they may encounter network problems like, low network bandwidth, loss of connection etc. which may require caching of results to reduce delay (Artail and Saab, 2009).
According to Buccafurri, F., P. De Meo, et al. (2009) the various QoS attributes involved for web services involving real time service provisioning such as streaming media are Response Time, Price, Availability, Reputation, Data quality timeliness, Data quality accuracy and Data quality completeness.
Kritikos, K. and D. Plexousakis (2007) broadly classify QoS parameter into two categories i.e., Domain Dependent QoS attributes and Domain Independent QoS attributes. These QoS attributes are used as evaluation criteria for web services based on their QoS Metrics. Figure 2 shows intuitive representation of this classification.
Figure 2: Classification of QoS Attributes (Kritikos, K. and D. Plexousakis, 2007)
3.6 Monitoring
Traditional software monitoring is done parallel to its execution; similarly the web service should be monitored in parallel to check if it is working according to the specification or requirement. Wang, Q., J. Shao, et al. (nd) suggests an approach where constraint specification are predefined and the web service is monitored against the constraints and any anomalies are notified. In this approach a probe is installed at the gateway of web service where the entire client traffic passes through. The probe feeds the central analyser where the QoS attributes are verified against the predefined constraint specification.
The QoS attributes which are to be monitored can be configured statically, but the dynamic nature of Internet sometimes demands it to be configured dynamically and this can be achieved by formalising the specification language. Gan, Y., M. Chechik, et al., (2009) identified that the subset of UML 2.0 can be used as a specification language to formalise and achieve the liveliness of the properties.
3.7 Web Services and Semantic Web
The web service discovery on a keyword based web is inefficient and their matching based on the keyword may not be accurate as the context may differ (Ma, J., J. Cao, et al., 2007). The semantic web services which utilise the power of Ontologies for matching and interchanging information will provide efficient and accurate matching based on the context.
Pathak, J., N. Koul, et al. (2005) has described a framework to discover web services which rely on user supplied Ontology specific mappings to match web services in specific domain to make it meaningful and accurate.
Cuevas-VicenttÌn, V., G. Vargas-Solar, et al. (2008) has presented a design and implementation of web service orchestration engine which provides scalable and robust platform for data management and semantic content across various domains. This will allow web services to automatically adapt to the requirements by discovering required service automatically.
3.8 Web Services in Organisations
The approach of the web services deals with an application integration concept. Web Services Technology is used in Organisations in two broad categories: EAI (Enterprise Application Integration) and B2B (Business-to-Business). ESB (Enterprise Service Bus) Infrastructure enables this integration which uses XML based web services to orchestrate the behaviour of services in distributed process.
3.8.1 Enterprise Application Integration
Enterprise systems integration permits applications to be connected in inter and intra organisational settings. EAI applications define unique data formats and communication protocols. These systems are complicated to change. The approach of the web services suggests a set of technologies which wraps the existing legacy systems as Web Services and integrates with the other systems within the organisation. Moreover, this integration approach permits the reusability of existing applications as well permitting new applications and data to be incorporated. For several organisations, the first and foremost implementations using Web services technology would be internal application integration, since that is the main difficulty for them to deal with IT (Ooi & Su, 2006).
3.8.2 B2B
B2B computing is integrating of business systems of two or more companies to support cross-enterprise business. In a matter of 5 years, the challenges of constructing Business to Business applications collective with the massive market potential initiated innovation that moves the industry from simple business-to-consumer (B2C) applications to SOAP-enabled Web services. Any of the open Internet protocols such as HTTP, SMTP, or FTP, or proprietary networks such as EDI is used by the B2B applications. B2C applications handle data directly over the HTTP protocol. (Cixing & Yunlong, 2009)
4 Evaluating Web Services - Case Study
In this case study http://zoomii.com an e-commerce website is evaluated which includes analysis of web services used in the website. This website was developed using Amazon Web SerivesTM and has been analysed based on the paradigms; Quality of Service (attributes listed in Section 3.5), Key Features and Drawbacks.
Zoomii (there after refers to http://zoomii.com) is a book seller website which lists top 25000 books available in amazon.com products list. Its cool interface (similar to Google Maps) allows users to search through the online book store as if they do it in a physical book shelves. It uses Amazon Web Services to get the best out of it. Users can pay for the books purchased online through Amazon FPS web service.
4.1 Website Architecture
Zoomii uses the following Amazon web services:
* Amazon Product Advertising API: formerly known as Amazon E-Commerce Service (ECS) is used to access the books data available in www.amazon.com store using web services (Zoomii Inc, 2009) and (Amazon.com, 2009). Though both REST and SOAP requests can be used to access the web services, Amazon.com (2009) recommends using REST as it is more intuitive and also SOAP requests would need toolkits which is not provided for all platforms and programming languages.
* Amazon Elastic Compute Cloud (Amazon EC2): is used to host the web server and computing infrastructure on which the Zoomii runs.
* Amazon Simple Storage Service (Amazon S3): is used for storing data which is specific to Zoomii such as profile information, images etc.
* Amazon Flexible Payments Service (Amazon FPS): is used for transactions through debit and credit cards.
4.2 Experimental Environment
The experiments were performed on a Laptop with the following specification.
Operating System: Windows XP
Processor: Intel Core 2 Duo - 2.4 GHz
RAM: 2 GB
HDD: 250 GB
Network: 20 Mbps broadband connection
The usability was evaluated in different browsers viz., Fire Fox, Internet Explorer, and Google Chrome. Additionally the usability was also evaluated in the touch interface of iPhone with WiFi connection (Same network used in Laptop).
4.3 Quality of Service
The following attributes (listed in Section 3.5) which has been selected for evaluation is as defined by Kritikos, K. and D. Plexousakis (2007).
4.3.1 Domain Dependent Attributes
Domain dependent attributes are related to the domain to which the web services belong to. Zoomii belongs to book seller domain and hence the attributes which are related to this domain are evaluated in this section.
4.3.1.1 Performance
This quality attribute determines how well the service performs. This is generally determined based on the response time. Due to the limitations and access restrictions, the response time for individual web services used in Zoomii cannot be measured. Hence the overall response time for the page load of each event was captured and analysed. The experimental results showed an average response time of 1.65 seconds which was acceptable for the intuitive look (book shelves).
Figure 2: Response time of Zoomii
4.3.1.2 Dependability
This quality attribute determines if the service can be justifiably trusted. This in turn is sufficed when the attributes Viz., Availability, Reliability and Scalability are sufficed.
Scalability: (Zoomii, 2009) has mentioned that the website can only retrieve top 25000 books from Amazon store. Also there are some limitations to the level of categorisation of books. Hence the scalability of this application is not appreciable. Author is working to improve the scalability. Figure 3 shows the screen shot of a page from Zoomii website showing the limitation.
Availability: The service is available 24×365 except during maintenance activities which could be minimal when planned. Amazon EC2 can be configured such that the web server can scale up or down depending upon the traffic and hence the site never goes down.
Reliability: It can be defined as the ability to perform under stated conditions. The web site retrieved results for all the trials which prove the service to be reliable. Also the server is highly scalable and the services are available 24×7, hence it is reliable.
Figure 3: Screen showing the about page of Zoomii
4.3.1.3 Transaction Support Related QoS
Transaction support determines the integrity of the data. Zoomii has features such as Wish List and Cart, where books can be added or deleted and maintained for different sessions. Each session has own instances of wish list and cart which don't interfere with each other. Thus the data integrity is maintained.
https://fps.sandbox.amazonaws.com?
Action=GetTransactionStatus
&AWSAccessKeyId=AKIAIIFXJCFIHITREP4Q
&Signature=2l60qD6%2BDIfVEN7ZiHM0AcUKACZt0GYKFtIryqkCb6g%3D
&SignatureMethod=HmacSHA256
&SignatureVersion=2
&Timestamp=2009-10-06T09%3A12%3A06.921Z
&TransactionId=14GKE3B85HCMF1BTSH5C4PD2IHZL95RJ2LM
&Version=2008-09-17"
The above REST request shows the sample request to get the transaction status. From this it is evident that the transactions is completely taken care by Amazon.
4.3.1.4 Security
Security can be evaluated based on the attributes such as authentication, authorisation, integrity, data encryption etc. Zoomii has a login mechanism (user id and password) using which authentication and authorisation occurs. Users can browse the website without logging in, but can check out the books only after logging in.
The code snippet presented below is a REST request for Item Search operation of the Amazon Product Advertising API. It uses AWSAccessKeyId parameter to authenticate Zoomii to use the web services provided by Amazon. This key pair is provided by Amazon when Zoomii first registered with them.
"http://ecs.amazonaws.com/onca/xml?
Service=AWSECommerceService
&AWSAccessKeyId=[AWS Access Key ID]
&Operation=ItemSearch&
SearchIndex=Books&
Author=Steve%20Davenport&
Version=2006-09-13"
Zoomii maintains user information and it stores password in clear text which is displayed in page source. Hence it is vulnerable to attacks; anyone monitoring network traffic can easily capture the confidential and private data.
Figure 3: Page Source Showing Clear Text Password
The payments are taken care by Amazon FPS web service which is a secure service. The communication is done through secure protocol in which the data is encrypted and hence this functionality of the website is secure.
4.3.2 Domain Independent Attributes
The attributes that are related to the technical aspects of the web services are evaluated in this section.
4.3.2.1 Usability
Zoomii's user interface which is similar to Google Maps is easy to use. Instead of traditions tree structure for categorisation, it has used intuitive way of zooming in and out of categories. All these features are good only with a scroll mouse; otherwise it is little bit difficult to navigate between categories.
Website is obsolete when used in a touch interface (Apple iPhone), i.e., the UI is completely not usable as the zoom in and zoom out feature conflicts with touch interface.
4.3.2.2 Data Encryption
Zoomii doesn't use any data encryption. All the payments are carried out through Amazon FPS which uses 128 bit encryption verified by VeriSign Class 3 Secure Server.
Figure 4: Security information of www.amazon.com
4.3.2.3 Reputation
The reputation of web services at the Amazon Product Advertising API level cannot be evaluated, but the overall reputation of Amazon Web Services is good as they are the leading web service providers in the market (DatacenterDynamics, 2009).
4.3.2.4 Price
Amazon web services charges only if the service is used. For instance they charge £ 0.08 for one hour usage of Amazon EC2 which is low-priced when compare to the cost of setting up such infrastructure.
4.4 Key Features
* Web Service provides access to several million items with good response time.
* Scaling up and down of servers happens automatically with Amazon EC2.
* Encrypted key value pair is used for authentication with Amazon.
* The user interface gives an intuitive look and is easy to use.
* Complete technical documentation and user support is available.
* E-Commerce design used here is object based which gives real world experience.
4.5 Drawbacks
* Web services doesn't contain enough QoS attributes to make if adapt to changes in environment.
* No synchronisation between Zoomii Cart and Amazon Cart.
* Preview facility is not available in Zoomii but available in Amazon book store.
* Drilling down into sub-categories is limited.
* User information is less secure.
* Only top 25000 ranking books rated in Amazon is available.
4.6 Proposals
* Making both Amazon and Zoomii fully semantic will help overcome the integration problems such as cart synchronisation.
* This could be extended to academic library catalogues.
* Security can be improved by including SSL Certificate.
* Personal book shelf features, where registered users can store and organise their books.
* Mouse hover display of useful information on books in layout mode.
* Drag and drop support for moving books.
4.7 Tools used for analysis
* Google Chrome, Fire Fox and Internet Explorer - The response time of the website was analysed in various browsers.
* Network Monitor 3.3 - Was used to analyse the network traffic and payloads of various operations in the website.
5 Conclusion
Computer to computer communication which can happen within companies or across companies, within domains or across domains are not standardised (Davies, N., D. Fensel, et al., 2004). The web services; an implementation of SOA under ESB infrastructure have facilitated a major breakthrough in terms of integration and communication between enterprises. The overall research across the world is oriented towards automating and improving the quality of web services. Semantic web services orchestrated with clearly defined QoS attributes can dynamically adapt and provide high quality of service in a fully semantic web. The case study on Zoomii proved that there are many drawbacks due to the limitations in integrating two websites. This can be facilitated by Semantic Web Services and fully Semantic Web. Hence the vision of web is moving towards fully semantic web which is called Web 3.0. Thus the study on Web Services; its current trends and future opportunities and evaluation of a web services has been performed.
6 Appendix - Acronyms
| Term | Definition |
|---|---|
| B2B | Business to Business |
| B2C | Business to Consumer |
| EAI | Enterprise Application Integration |
| EDI | Electronic Data Interchange |
| ESB | Enterprise Service Bus |
| FTP | File Transfer Protocol |
| HTTP | Hyper Text Transfer Protocol |
| QoS | Quality of Service |
| QWS | Quality of Web Service |
| SLA | Service Level Agreement |
| SMTP | Simple Mail Transfer Protocol |
| SOA | Service Oriented Architecture |
| SOAP | Simple Object Access Protocol |
| W3C | World Wide Web Consortium |
| WS | Web Service |
| WSDi | Web Service Discovery |
| WSDL | Web Services Description Language |
| UBR | UDDI Business Registry |
| XML | Extensible Mark-up Language |
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