Web Services - Current Trends and Future
Opportunities Comments
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
1 Abstract
2 Introduction
3 Web Services
3.1 SOA with Web Services
3.2 Description
3.3 Discovery
3.4 Requirements
3.5 QoS Attributes (Evaluation Criteria)
3.6 Monitoring
3.7 Web Services and Semantic Web
3.8 Web Services in Organisations
3.8.1 Enterprise Application Integration
3.8.2 B2B
4 Evaluating Web Services - Case Study
4.1 Website Architecture
4.2 Experimental Environment
4.3 Quality of Service
4.4 Key Features
4.5 Drawbacks
4.6 Proposals
4.7 Tools used for analysis
5 Conclusion
6 Appendix - Acronyms
7 References
^table of contents^
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.
^table of contents^
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.
^table of contents^
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)
^table of contents^
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.
^table of contents^
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.
^table of contents^
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 |
^table of contents^
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