SOA Journal by Traitet Th.
Download as DOCX, PDF0 likes337 views
This paper critically analyzes top-down and bottom-up approaches in service-oriented architecture (SOA) development, highlighting their distinct contexts: strategic alignment, service delivery, and operational implementation. The top-down approach, initiated by management, aims for alignment with business strategies but requires more time and cost, while the bottom-up approach starts with immediate business needs and can lead to reduced initial development efforts, but may face challenges in scalability and service redundancy. Ultimately, combining both approaches is proposed as an effective strategy for successful SOA implementation.
![Developing a Web service by using a code-first approach makes it easy to convert a legacy code into a
Web service, and it also takes much less time to create a WSDL contract (Suriarachchi 2010). However,
by using this approach, XML Schema Definitions (XSDs) will be contained in the WSDL contract.
Therefore, when a XML schema definition is changed according to a business objecte.g. changing a data
type,developers must not only regenerate WSDL code, but they are also needed to inform this change to
all consumers in order to modify their consuming code. On the other hand, by using a contract-first
approach, developers can include business objects into their Web service classes. As a result, they are
flexible to modify those business objects without republishing WSDL files. Furthermore, the first-code
approach enables a XSD file can be used by several services. It is an effective way of enhancing
reusability of services in developing SOA (Vivek 2009).
Conclusion
To sum up, this paper analysesusing top-down and bottom-up approaches to developing SOA in three
different contexts: strategic level, service delivery and operational level.Firstly, in the context of business
strategy, a top-down approach initiated by top management enables SOA solutions to align with overall
business strategies and requirements, but it takes more effort and cost. Secondly, in terms of service
delivery, a top-down approach needs a lot of time to establish a service inventory blueprint, whereas a
bottom-up approach starting with immediate business requirements can reduce time and the scope ofthe
SOA project.However, development of consequent SOA services will take more time, expenditure and
effortthan a bottom-up approach. Lastly, in terms operational level in developing Web services, a bottom-
up or code-first approach is easier to develop than a top-down or contract-first approach because WSDL
can be generated automatically, but using the top-down method can enhance reusability of services and
flexibility to change business objectsor XML schema definitionswithout republishing a WSDL contract.
References
ABDOLLAH, Tina (2007). Building a successful SOA project. [online]. Last accessed 7 May 2012 at:
http://www.ibm.com/developerworks/library/ar-buildsoa
DELSING, Jerker, et al. (2011). A migration approach towards a SOA-based next generation process control and
monitoring. In: IECON 2011 - 37th Annual Conference on IEEE Industrial Electronics Society, 7-10 November 2011.
ERL, Thomas (2008). SOA: Principles of Service Design. Boston, Pearson Education.
GANGULY Kuntal, GOSWAMI, Partha (2011). Developing Web Services. [online]. Last accessed 7 May 2012 at:
http://www.ibm.com/developerworks/webservices/library/ws-devaxis2part1/index.html
JOSUTTIS, Nicolai M. (2007). SOA in Practice: The Art of Distributed System Design. USA, O'Reilly Media.
KRAFZIG, Dirk, BANKE, Karl, SLAMA, Dirk (2005). Enterprise SOA: Service-Oriented Architecture Best Practices.
USA, Pearson Education.
MARGOLIS, Ben (2007). SOA for Business Developer. USA, MC Press.
POMARES, William Martinez (2010). The Top-Down vs Bottom-Up SOA Debate Revisited. [online]. Last accessed 6
May 2012 at: http://www.infoq.com/news/2010/07/top-down-bottom-up-soa
SHAHRBANOO, Majlesi, ALI, Mehrpour and MEHRAN, Mohsenzadeh (2012). An approach for agile SOA
development using agile principals. International journal of computer science & information technology, 4(1), 237-244.
SURIARACHCHI, Isuru (2010). Code First or Contract First with WSO2 Web Services Application Server? [online].
Last accessed 6 May 2012 at: http://wso2.org/library/articles/code-first-or-contract-first-wso2-wsas
TERE, G. M. and JADHAV, B. T. (2012). Designing application framework using WSDL. In: IJCA Proceedings on
International Conference and Workshop on Emerging Trends in Technology (ICWET 2012), Foundation of Computer
Science (FCS), 27-32.
VIVEK (2009). Developing Web Service - Top-Down vs Bottom-Up approach. [online]. Last accessed 7 May 2012 at:
http://oracled.wordpress.com/2009/12/25/developing-web-service-top-down-vs-bottom-up-approach
WALKER, L. (2007). IBM business transformation enabled by service-oriented architecture. IBM systems journal, 46
(4), 651-667.
3](https://image.slidesharecdn.com/ws11may12-120530161851-phpapp02/85/SOA-Journal-by-Traitet-Th-3-320.jpg)
SOA Journal by Traitet Th.
- 1. Critical Context-based Analysis of Top-down and Bottom-up Approaches in SOA Development Traitet Thepbandansuk Abstract Service-Oriented Architecture (SOA) is widely recognised as a potential architecture for aligning business and IT strategies by heterogeneous systemintegration. Development of SOA by using a top-down approach focuses on business-driven strategiesto align IT with business, whereas that by using a bottom- up approach focuses on technology-driven processes to align business with IT. To successfully develop SOA, top-down and bottom-up approaches have been discussed in various contexts. This paper provides critical context-based analysis of two commonly usedapproachesin SOA development. Introduction SOA is extensively accepted as a suitable architectural style for designing and developing software in terms of interoperable services.In general, they are often implemented as Web servicesto support interoperability between various application development platforms (Margolis 2008). There are two oppositescommonly used as approachesto develop SOA,namely top-down and bottom-up. These days, an appropriate approach that should be employed in developing SOA and Web services is a controversial issue leading to much debate. There is a widespread perception that using a top-down approach can enhance reusability and enable SOA projects to meet business requirements; however, others take a different stance. This paper criticallyanalyses and evaluates both views in three distinctive contexts: strategic level, service delivery and operational level, as illustrated in Figure 1 and the following sections. Figure 1 Top-down and bottom-up approachesin SOA development (Josuttis 2007; Erl 2008; Krafzig, Banke and Slama 2005) 1
- 2. Context of the Strategic Level in Terms of Project Initiation A top-down approach is a methodologyto align IT infrastructure with business strategies. As can be seen in Figure 1, in terms of project creation, this approach is initiated by top management who would like to build a flexible business model, which can rapidly adapt to changes in the market-place (Sharbanoo, Ali and Mehran 2012). Then, execution teams implementSOA solutions following business strategies by developing IT infrastructure in-line with thebusiness process modelrequriements.Conversely, a bottom-up approach aligns business processes with IT infrastructure,especially business applications. This methodstarts with a small group of SOA enthusiasts, such as a particular department or business unit. After the first pilot project is successful, execution teams gradually implement other projects, and ultimately end with an enterprise-wide rollout (Josuttis 2007). However, Abdollah (2007) suggests that building SOA solutionsin practice by only working downward or upward it is not easy to become successful, especially for medium to large businesses.Therefore, combining both approaches is an effective way. The bottom-up method can reduce time, effort and cost of developing SOA services, whereas the top-down initiated by top management can develop business process-driven services, which enable business agility and flexibility to make sure that long-term business goals, business strategies and requirements are addressed (Josuttis 2007; Walker 2007). Context of Service Delivery Atop-down approach in terms of service delivery starts with inventory analysis in order to designa service inventory blueprint known as a service enterprise model. Then,the services required by a new business model are developed and delivered.On the contrary, a bottom-up approach focuses on service-oriented analysis to fulfill immediate business requirements as the first priority. Although using the top-down approach needs much higher investment and time to analyse business processes to produce a blueprint comprising of a collection of standardised services, the overall burden of subsequent service governance is reduced because the SOA services had been modeled since the first implementation stage(Erl 2008). However, Worker (2007) suggests that using the top-down approach for large businessesrequiresan effective collaboration between multiple business units with various business strategies. Furthermore, using a bottom-up approach starts with service-oriented analysis that does not need to produce a blueprint. This method can save costs, effort and time to deliver initial services (Erl 2008). Nevertheless, it requires more expenses and time for updating and reworking when developing new services or changing business requirements. Moreover, it tends to result in redundant SOA services;also the services developed may not support the business requirements(Pomares 2010; Delsing 2011). Context of the Operational Level in Terms of Implementing Web Services Web Service Definition Language (WSDL) is an XML-based language for explainingdetails of Web services (Margolis 2007). WSDL is also used to define anSOA contract including interface information between a Web serviceand its consumers (Tere 2012). Building Web services by using a top-down or contract-first approach begins with defining a WSDL contract, and then coding Web services as shown in Figure 1 (Suriarachchi 2010). In contrast, a bottom-up or code-first approach starts with coding Web services. Next, a WSDL contract can be automatically generated when deploying the Web services to a Web service engine, such as Apache Axis2 for java and .NET (Ganguly and Goswami 2011). 2
- 3. Developing a Web service by using a code-first approach makes it easy to convert a legacy code into a Web service, and it also takes much less time to create a WSDL contract (Suriarachchi 2010). However, by using this approach, XML Schema Definitions (XSDs) will be contained in the WSDL contract. Therefore, when a XML schema definition is changed according to a business objecte.g. changing a data type,developers must not only regenerate WSDL code, but they are also needed to inform this change to all consumers in order to modify their consuming code. On the other hand, by using a contract-first approach, developers can include business objects into their Web service classes. As a result, they are flexible to modify those business objects without republishing WSDL files. Furthermore, the first-code approach enables a XSD file can be used by several services. It is an effective way of enhancing reusability of services in developing SOA (Vivek 2009). Conclusion To sum up, this paper analysesusing top-down and bottom-up approaches to developing SOA in three different contexts: strategic level, service delivery and operational level.Firstly, in the context of business strategy, a top-down approach initiated by top management enables SOA solutions to align with overall business strategies and requirements, but it takes more effort and cost. Secondly, in terms of service delivery, a top-down approach needs a lot of time to establish a service inventory blueprint, whereas a bottom-up approach starting with immediate business requirements can reduce time and the scope ofthe SOA project.However, development of consequent SOA services will take more time, expenditure and effortthan a bottom-up approach. Lastly, in terms operational level in developing Web services, a bottom- up or code-first approach is easier to develop than a top-down or contract-first approach because WSDL can be generated automatically, but using the top-down method can enhance reusability of services and flexibility to change business objectsor XML schema definitionswithout republishing a WSDL contract. References ABDOLLAH, Tina (2007). Building a successful SOA project. [online]. Last accessed 7 May 2012 at: http://www.ibm.com/developerworks/library/ar-buildsoa DELSING, Jerker, et al. (2011). A migration approach towards a SOA-based next generation process control and monitoring. In: IECON 2011 - 37th Annual Conference on IEEE Industrial Electronics Society, 7-10 November 2011. ERL, Thomas (2008). SOA: Principles of Service Design. Boston, Pearson Education. GANGULY Kuntal, GOSWAMI, Partha (2011). Developing Web Services. [online]. Last accessed 7 May 2012 at: http://www.ibm.com/developerworks/webservices/library/ws-devaxis2part1/index.html JOSUTTIS, Nicolai M. (2007). SOA in Practice: The Art of Distributed System Design. USA, O'Reilly Media. KRAFZIG, Dirk, BANKE, Karl, SLAMA, Dirk (2005). Enterprise SOA: Service-Oriented Architecture Best Practices. USA, Pearson Education. MARGOLIS, Ben (2007). SOA for Business Developer. USA, MC Press. POMARES, William Martinez (2010). The Top-Down vs Bottom-Up SOA Debate Revisited. [online]. Last accessed 6 May 2012 at: http://www.infoq.com/news/2010/07/top-down-bottom-up-soa SHAHRBANOO, Majlesi, ALI, Mehrpour and MEHRAN, Mohsenzadeh (2012). An approach for agile SOA development using agile principals. International journal of computer science & information technology, 4(1), 237-244. SURIARACHCHI, Isuru (2010). Code First or Contract First with WSO2 Web Services Application Server? [online]. Last accessed 6 May 2012 at: http://wso2.org/library/articles/code-first-or-contract-first-wso2-wsas TERE, G. M. and JADHAV, B. T. (2012). Designing application framework using WSDL. In: IJCA Proceedings on International Conference and Workshop on Emerging Trends in Technology (ICWET 2012), Foundation of Computer Science (FCS), 27-32. VIVEK (2009). Developing Web Service - Top-Down vs Bottom-Up approach. [online]. Last accessed 7 May 2012 at: http://oracled.wordpress.com/2009/12/25/developing-web-service-top-down-vs-bottom-up-approach WALKER, L. (2007). IBM business transformation enabled by service-oriented architecture. IBM systems journal, 46 (4), 651-667. 3