http://www.youtube.com/watch?v=WMNzOCemKko
http://www.youtube.com/watch?v=b22vAQbb_jM
Friday, November 26, 2010
what is SOA?
SOA has become a de-facto standard for system development and integration of new with existing legacy solutions running and supporting complex business processes.SOA, as IT world has always a fancy term for any new technology,elaborates to Serivce Oriented Architecture, is not a new term and has been around with emergence of webservices.
In order to understand SOA, we must first understand what a webservice means, which is sometimes referred as crux of SOA,not always though.A system does not necessarily need to use web services and all related standards to be "service-oriented." For example, some service oriented systems have been implemented using Corba,DCOM,RPC, Jini and REST.A webservice is defined by a set of processes over a network which is a manifestation of some physical entities like databases,devices,programs.It is an interface or gateway for one program/device/system to have a controlled access over a network to other program/device/system like humans need some sort of GUI to interact with one system.A webservice accepts a command as a SOAP envelope to expedite some task and sends response in a form of SOAP envelope too.SOAP(Simple Object Access Protocol) is protocol which uses XML based messages generally over HTTP.A webservice is loosely coupled and flexible , it means a consumer of a web service is not tied to that web service directly; the web service interface can change over time without compromising the client's ability to interact with the service. A tightly coupled system implies that the client and server logic are closely tied to one another, implying that if one interface changes, the other must also be updated. Adopting a loosely coupled architecture tends to make software systems more manageable and allows simpler integration between different systems.
Apart from SOAP, other key constituents of a webservice are WSDL and UDDI.
WSDL(Web Services Description Language) is an XML technology that describes the interface of a web service in a standardized way. WSDL standardizes how a web service represents the input and output parameters of an invocation externally, the functions' structure, the nature of the invocation (in only, in/out, etc.), and the service's protocol binding. WSDL allows disparate clients to automatically understand how to interact with a web service.
UDDI(Universal Description, Discovery, and Integration - An XML-based registry to publish service descriptions (WSDL) and allow their discovery.UDDI is used to discover available webservices by searching for names,identifiers,categories or specifications implemented by the web service.
SOA is an extension to EAI(Enterprise Application Integration), which is technology independent whether it is Java,.Net,CORBA or webservices.This has given rise to enormous potential of varied and vast scope of application integration in fast changing,ever evolving and getting more and more complex business requirements.Since the large organizations have lot of existing systems over different geographical locations,with different operating systems using different technologies doing different business operations, these organizations have found SOA as a big solution to their burgeoning problem of keeping their IT budgets in control vis a vis addressing their growing business requirements.The continuous IT growth within organizations have given rise to a new level of complexity and challenge to bind existing legacy,business critical solutions with new ones and that's where SOA fits in putting all different pieces together.When all the hype associated with SOA will reside and organizations will get more close to reality then its fruits will be reaped.
SOA has some ground features which drives development and maintenance of SOA based solutions:
In order to understand SOA, we must first understand what a webservice means, which is sometimes referred as crux of SOA,not always though.A system does not necessarily need to use web services and all related standards to be "service-oriented." For example, some service oriented systems have been implemented using Corba,DCOM,RPC, Jini and REST.A webservice is defined by a set of processes over a network which is a manifestation of some physical entities like databases,devices,programs.It is an interface or gateway for one program/device/system to have a controlled access over a network to other program/device/system like humans need some sort of GUI to interact with one system.A webservice accepts a command as a SOAP envelope to expedite some task and sends response in a form of SOAP envelope too.SOAP(Simple Object Access Protocol) is protocol which uses XML based messages generally over HTTP.A webservice is loosely coupled and flexible , it means a consumer of a web service is not tied to that web service directly; the web service interface can change over time without compromising the client's ability to interact with the service. A tightly coupled system implies that the client and server logic are closely tied to one another, implying that if one interface changes, the other must also be updated. Adopting a loosely coupled architecture tends to make software systems more manageable and allows simpler integration between different systems.
Apart from SOAP, other key constituents of a webservice are WSDL and UDDI.
WSDL(Web Services Description Language) is an XML technology that describes the interface of a web service in a standardized way. WSDL standardizes how a web service represents the input and output parameters of an invocation externally, the functions' structure, the nature of the invocation (in only, in/out, etc.), and the service's protocol binding. WSDL allows disparate clients to automatically understand how to interact with a web service.
UDDI(Universal Description, Discovery, and Integration - An XML-based registry to publish service descriptions (WSDL) and allow their discovery.UDDI is used to discover available webservices by searching for names,identifiers,categories or specifications implemented by the web service.
SOA is an extension to EAI(Enterprise Application Integration), which is technology independent whether it is Java,.Net,CORBA or webservices.This has given rise to enormous potential of varied and vast scope of application integration in fast changing,ever evolving and getting more and more complex business requirements.Since the large organizations have lot of existing systems over different geographical locations,with different operating systems using different technologies doing different business operations, these organizations have found SOA as a big solution to their burgeoning problem of keeping their IT budgets in control vis a vis addressing their growing business requirements.The continuous IT growth within organizations have given rise to a new level of complexity and challenge to bind existing legacy,business critical solutions with new ones and that's where SOA fits in putting all different pieces together.When all the hype associated with SOA will reside and organizations will get more close to reality then its fruits will be reaped.
SOA has some ground features which drives development and maintenance of SOA based solutions:- Extensibility
- Interoperability
- Loose Coupling
- Reusablity
- Granularity
- Modularization
- Componentization
- Services Identification and categorization
- Services Provisioning and delivery
- Services Monitoring and tracking
- Basics of Object Oriented Technology like Abstraction,Encapsulation
SOA QUESTIONS -26th NOV-2010
What are the main benefits of SOA ?
SOA helps create greater alignment between IT and line of business while generating more flexibility - IT flexibility to support greater business flexibility. Your business processes are changing faster and faster and global competition requires the flexibility that SOA can provide.
SOA can help you get better reuse out of your existing IT investments as well as the new services you’re developing today. SOA makes integration of your IT investments easier by making use of well-defined interfaces between services. SOA also provides an architectural model for integrating business partners’, customers’ and suppliers’ services into an enterprise’s business processes. This reduces cost and improves customer satisfaction
What is a reusable Service?
It is an autonomous, reusable, discoverable, stateless functionality that has the necessary granularity, and can be part of a composite application or a composite service.
A reusable service should be identified with a business activity described by the service specifications (design-time contract).
A service’s constraints, including security, QoS, SLA, usage policies, may be defined by multiple run-time contracts, multiple interfaces (the WSDL for a SOAP Web Service), and multiple implementations (the code).
A reusable service should be governed at the enterprise level throughout its entire lifecycle, from design-time through run-time. Its reuse should be promoted through a prescriptive process, and that reuse should be measured.
Talking about Service identification, which approach between top-down and bottom-up methodologies encourages re-use and mantainance ?
Since the top-down approach is business-driven it can be practical to separate the different concerns of business and IT on different plans, providing a common ground in between. So in most situations it the most appropriate if you want to improve reuse and ROI in the medium/long term. Anyway
How can you achieve loose coupling in a soa ?
One strategy for achieving loose coupling is to use the service interface (the WSDL for a SOAP Web Service) to limit this dependency, hiding the service implementation from the consumer. Loose coupling can be addressed by encapsulating the service functionalities in a manner that limits the impact of changes to the implementation on the service interface. However, at some point you will need to change the interface and manage versioning without impacting service consumers, in addition to managing multiple security constraints, multiple transports, and other considerations
Do you recall any pattern which could be use to leverage loose coupling ?
The Mediation pattern, using an enterprise service bus (ESB), will help in achieving this.
Mediation will take loose coupling to the highest level. It will establish independence between consumers and providers on all levels, including message formats, message types (including SOAP, REST, XML, binary) and transport protocols (including HTTP, HTTPS, JMS).
Architecturally speaking this means the separation of concerns between consumers and providers on the transport, message type, and message format levels.
The Service of a SOA should be engineered as stateless or stateful ?
Service should be stateless. It may have a context within its stateless execution, but it will not have an intermediary state waiting for an event or a call-back. The retention of state-related data must not extend beyond a request/response on a service. This is because state management consumes a lot of resources, and this can affect the scalability and availability that are required for a reusable service.
What is composition of a Service ?
Composition is the process by which services are combined to produce composite applications or composite services. A composite application consists of the aggregation of services to produce an enterprise portal or enterprise process. A composite service consists of an aggregation of services that produces another reusable service. It’s just like combining electronic components to create a computer motherboard, and then using that motherboard in a computer. Think of the motherboard as a reusable composite service that is a component of the computer, and of the computer as the composite application.
How do I integrate my Legacy applications with SOA ?
Legacy applications are frequently at the core of your IT environment. With the right skills and tools, you need to identify discrete elements within your legacy applications and “wrap” them in standards-based interfaces and use them as services within your SOA.
How does the ESB fits in this picture ?
The Enterprise Service Bus is a core element of any SOA. ESBs provide the “any to any” connectivity between services within your own company, and beyond your business to connect to your trading partners. But SOA does not stop at just implementing an ESB. Depending on what your goals are, you may want to use an ESB to connect other services within your SOA such as information services, interaction services and business process management services. Additionally, you will need to consider development services and IT service management services. The SOA reference architecture can help you lay out an SOA environment that meets your needs and priorities. The ESB is part of this reference architecture and provides the backbone of an SOA but it should not be considered an SOA by itself.
What are the common pitfalls of SOA ?
One of the most common pitfalls is to view SOA as an end, rather than a means to an end. Developers who focus on building an SOA solution rather than solving a specific business problem are more likely to create complex, unmanageable, and unnecessary interconnections between IT resources.
Another common pitfall is to try to solve multiple problems at once, rather than solving small pieces of the problem. Taking a top-down approach—starting with major organization-wide infrastructure investments—often fails either to show results in a relevant timeframe or to offer a compelling return on investment.
Contract is an agreement between two or more parties. It defines the protocol how client should communicate with your service. Technically, it describes parameters and return values for a method.
An Address indicates where we can find this service. Address is a URL, which points to the location of the service.
Bindings determine how this end can be accessed. It determines how communications is done. For instance, you expose your service, which can be accessed using SOAP over HTTP or BINARY over TCP. So for each of these communications medium two bindings will be created.
Below figure, show the three main components of end. You can see the stock ticker is the service class, which has an end hosted on www.soa.com with HTTP and TCP binding support and using Stock Ticker interface type.
The concept of SOA is nothing new, however why everyone started to talk about SOA only in the last years ?
Yes I agree the basic concept of SOA aren’t new, however some technology technology changes in the last 10 years made service-oriented architecture more practical and applicable to more organizations than it was previously. Among this:
What is the most important skill you need to adopt SOA ? technical or cultural ?
Surely cultural. SOA does require people to think of business and technology differently. Instead of thinking of technology first (e.g., If we implement this system, what kinds of things can we do with it?), practitioners must first think in terms of business functions, or services (e.g., My company does these business functions, so how can I set up my IT system to do those things for me most efficiently?).It is expected that adoption of SOA will change business IT departments, creating service-oriented (instead of technology-oriented) IT organizations.
SOA helps create greater alignment between IT and line of business while generating more flexibility - IT flexibility to support greater business flexibility. Your business processes are changing faster and faster and global competition requires the flexibility that SOA can provide.
SOA can help you get better reuse out of your existing IT investments as well as the new services you’re developing today. SOA makes integration of your IT investments easier by making use of well-defined interfaces between services. SOA also provides an architectural model for integrating business partners’, customers’ and suppliers’ services into an enterprise’s business processes. This reduces cost and improves customer satisfaction
What is a reusable Service?
It is an autonomous, reusable, discoverable, stateless functionality that has the necessary granularity, and can be part of a composite application or a composite service.
A reusable service should be identified with a business activity described by the service specifications (design-time contract).
A service’s constraints, including security, QoS, SLA, usage policies, may be defined by multiple run-time contracts, multiple interfaces (the WSDL for a SOAP Web Service), and multiple implementations (the code).
A reusable service should be governed at the enterprise level throughout its entire lifecycle, from design-time through run-time. Its reuse should be promoted through a prescriptive process, and that reuse should be measured.
Talking about Service identification, which approach between top-down and bottom-up methodologies encourages re-use and mantainance ?
Since the top-down approach is business-driven it can be practical to separate the different concerns of business and IT on different plans, providing a common ground in between. So in most situations it the most appropriate if you want to improve reuse and ROI in the medium/long term. Anyway
How can you achieve loose coupling in a soa ?
One strategy for achieving loose coupling is to use the service interface (the WSDL for a SOAP Web Service) to limit this dependency, hiding the service implementation from the consumer. Loose coupling can be addressed by encapsulating the service functionalities in a manner that limits the impact of changes to the implementation on the service interface. However, at some point you will need to change the interface and manage versioning without impacting service consumers, in addition to managing multiple security constraints, multiple transports, and other considerations
Do you recall any pattern which could be use to leverage loose coupling ?
The Mediation pattern, using an enterprise service bus (ESB), will help in achieving this.
Mediation will take loose coupling to the highest level. It will establish independence between consumers and providers on all levels, including message formats, message types (including SOAP, REST, XML, binary) and transport protocols (including HTTP, HTTPS, JMS).
Architecturally speaking this means the separation of concerns between consumers and providers on the transport, message type, and message format levels.
The Service of a SOA should be engineered as stateless or stateful ?
Service should be stateless. It may have a context within its stateless execution, but it will not have an intermediary state waiting for an event or a call-back. The retention of state-related data must not extend beyond a request/response on a service. This is because state management consumes a lot of resources, and this can affect the scalability and availability that are required for a reusable service.
What is composition of a Service ?
Composition is the process by which services are combined to produce composite applications or composite services. A composite application consists of the aggregation of services to produce an enterprise portal or enterprise process. A composite service consists of an aggregation of services that produces another reusable service. It’s just like combining electronic components to create a computer motherboard, and then using that motherboard in a computer. Think of the motherboard as a reusable composite service that is a component of the computer, and of the computer as the composite application.
How do I integrate my Legacy applications with SOA ?
Legacy applications are frequently at the core of your IT environment. With the right skills and tools, you need to identify discrete elements within your legacy applications and “wrap” them in standards-based interfaces and use them as services within your SOA.
How does the ESB fits in this picture ?
The Enterprise Service Bus is a core element of any SOA. ESBs provide the “any to any” connectivity between services within your own company, and beyond your business to connect to your trading partners. But SOA does not stop at just implementing an ESB. Depending on what your goals are, you may want to use an ESB to connect other services within your SOA such as information services, interaction services and business process management services. Additionally, you will need to consider development services and IT service management services. The SOA reference architecture can help you lay out an SOA environment that meets your needs and priorities. The ESB is part of this reference architecture and provides the backbone of an SOA but it should not be considered an SOA by itself.
What are the common pitfalls of SOA ?
One of the most common pitfalls is to view SOA as an end, rather than a means to an end. Developers who focus on building an SOA solution rather than solving a specific business problem are more likely to create complex, unmanageable, and unnecessary interconnections between IT resources.
Another common pitfall is to try to solve multiple problems at once, rather than solving small pieces of the problem. Taking a top-down approach—starting with major organization-wide infrastructure investments—often fails either to show results in a relevant timeframe or to offer a compelling return on investment.
What’s the difference between services and components?
Services are logical grouping of components to achieve business functionality. Components are implementation approaches to make a service. The components can be in JAVA, C#, C++ but the services will be exposed in a general format like Web Services.What are ends, contract, address, and bindings?
These three terminologies on which SOA service stands. Every service must expose one or more ends by which the service can be available to the client. End consists of three important things where, what and how:-Contract is an agreement between two or more parties. It defines the protocol how client should communicate with your service. Technically, it describes parameters and return values for a method.
An Address indicates where we can find this service. Address is a URL, which points to the location of the service.
Bindings determine how this end can be accessed. It determines how communications is done. For instance, you expose your service, which can be accessed using SOAP over HTTP or BINARY over TCP. So for each of these communications medium two bindings will be created.
Below figure, show the three main components of end. You can see the stock ticker is the service class, which has an end hosted on www.soa.com with HTTP and TCP binding support and using Stock Ticker interface type.
Yes I agree the basic concept of SOA aren’t new, however some technology technology changes in the last 10 years made service-oriented architecture more practical and applicable to more organizations than it was previously. Among this:
- Universally-accepted industry standards such as XML, its many variants, and Web-services standards have contributed to the renewed interest in SOA.
- Data governance frameworks, which are important to a successful SOA implementation, have well test and refined over the years.
- A variety of enabling technologies and tools (e.g., modeling, development, infrastructure/middleware, management, and testing) have matured.
What is the most important skill you need to adopt SOA ? technical or cultural ?
Surely cultural. SOA does require people to think of business and technology differently. Instead of thinking of technology first (e.g., If we implement this system, what kinds of things can we do with it?), practitioners must first think in terms of business functions, or services (e.g., My company does these business functions, so how can I set up my IT system to do those things for me most efficiently?).It is expected that adoption of SOA will change business IT departments, creating service-oriented (instead of technology-oriented) IT organizations.
Is SOA really needed on your opinion?
SOA is not for everyone. While SOA delivers significant benefits and cost savings, SOA does require disciplined enforcement of centralized governance principals to be successful. For some organizations, the cost of developing and enforcing these principals may be higher than the benefits realized, and therefore not a sound initiative.
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