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Tuesday 2 March 2010

Scheduled exam S90.02

I've scheduled the second exam, SOA Technology Concepts, in my pursuit of becoming a Certified SOA Consultant for March 29. This exams covers the basic technologies to implement a SOA solutions, specially through the use of web services.

To prepare for this exam I've been reading chapters 5-6-7-13-16-17-18 of the book SOA: Concepts, Technology, and Design, I went through the course booklet and I've been listening to the cd's with the module overview, exam preparation and podcasts on different web services related subjects.

Sunday 7 February 2010

Understanding SOA - A Word On Services

Introduction

A service is the essential artifact in SOA, everything revolves around it, you'll be analyzing, modeling, designing, implementing, governing and versioning services. A service is a specialized piece of business logic, a piece of software that is designed by following the ideas, principles and patterns in mind that will fulfill a specific business need. Finally, some logic implemented as a web service is not automatically a (SOA) service.

Classifying services

When you're modeling and designing services you'll see that most services can be classified as a Utility, Entity or Task service:

- utility services: these are the services that don't have any real business knowledge and they are the most agnostic, this gives them the highest reuse potential. Utility services could encapsulate logging, notification,...

- entity services: these will most likely support CRUD operations on business entities such as clients and orders. Although they are working with business entities they are still very business agnostic, they don't have any knowledge of the business process that is using them. This gives them a also a high reuse potential.

- task services: they are specialized in executing a specific business task and so they have specific business knowledge and rules, this makes them less likely candidates to be reused

Modeling/designing services ...

Before you start a specific service implementation think about the big picture first and make an enterprise service blueprint. This is a high level overview of the services that will probably be needed by the enterprise. It will give you more guidance, direction, help set priorities and avoid future overlap between services.

Business is at the core of a SOA solution so everything starts by a specific business need that needs to be fulfilled. Then it's no surprise that the SOA delivery life cycle starts with the business analysis. When this is done the service modeling can start, this is to conceptualize the services that will fulfill the business need, this must be done by the business analyst and architect to keep the business and services aligned. Now comes the design fase, here the final services are chosen and get their technical design from the architect. Now the actual development of the services can start. A future article will go into more detail about the SOA delivery life cycle.

Always keep the principles and goals of SOA in your mind, are the services loosely coupled, do I have a standardize service contract, what will be the impact on the governance... Make every service as specialized and agnostic as you can, this will greatly enhance their reuse potential and avoid overlap with other services.

Service Implementations

Once your services are designed you can start implementing them. The technology that you'll be using is up to you, you're not limited by only SOAP based web services. The services can be also implemented as components or REST services. You don't necessary need to use an "open" technology, if your enterprise is completely Microsoft oriented you could use WCF over TCP with binary encoding and you would still be doing SOA.

Wednesday 27 January 2010

New Poll: Do you consider getting SOA certified?

Checkout the new poll on top of the right sidebar.

Are you thinking about getting somekind of SOA certification, are you busy getting one, do you already have one or are you not interested? If you have any remarks, questions, opinions or experience on the subject of this poll then let us know by commenting here.

Thursday 21 January 2010

Passed Exam S90.01: Fundamental SOA & Service-Oriented Computing

This morning I went to take the exam S90.01 and passed without too much difficulties, 96/100 isn't that bad I guess :-)

This exam is to test your basic understanding of Service-Orientation, here is a list of the things you have to be familiar with:
- services and related stuff (contracts, inventories...)
- delivery lifecycle
- the 8 principles
- the 7 strategic goals and benefits
- the 4 characteristics

You don't need to memorize them or know every aspect of them but be familiar with the terms and understand their meaning and the relationships between them.

The exam consists of 50 questions, these can be true/false, single choice or multiple choice questions. The pass rate is 80 and you have 1 hour to finish, this is more than enough time. I went over the questions in about 30 minutes then went over them again and was completely finished after 45 minutes.

As for the study materials, basically you have enough with the book SOA: Principles of Service Design. You don't need to read the entire book but I suggest you do this anyway, compared to the other books this one is still a modest sized book and you'll need it for the other exams as well. I also bought the course materials and this is quite handy to repeat the course once you read the book, you can go through it in 1 hour to refresh your knowledge.

Hope this was useful and as always, if you have any questions just shout (but don't ask to get sample questions).

Understanding SOA - Principles - Service Loose Coupling

Introduction

Service Loose Coupling means that each service is an isolated entity with limited dependencies on other (shared) resources. These resources could be technologies, (legacy) applications, databases, components, API's, infrastructure... The more a service is isolated from external resources the more predictable and reliable it will be. Don't start thinking that you can't have dependencies/relationships between services, service compositions are essential to SOA and is also one of the SOA principles but services shouldn't share the same underlying resources such as a database.

Standardized Service Contract

Service Loose Coupling also means that the service contract should be created with this principle in mind. When the contract is generated from a developer tool or runtime environment you automatically make the service dependent on that technology and so the service implementation and consumers will also be dependent on that technology.

Good Coupling and Bad Coupling

By now you should have realized that some types of coupling are good (allowed) and some are not good (or should be limited) and some are necessary. Coupling a service to a service contract is good but not the other way. Coupling between services is good, services must be composed to to create new business capabilities. Eventually the service will be coupled to a specific technology and runtime, this is necessary, you must develop your service with some technology but avoid the coupling of you contract to a specific technology.

Wednesday 20 January 2010

Understanding SOA - Principles - Service Contract

Introduction
The service contract is probably the most important thing/document/artifact that you'll be creating or using concerning a SOA implementation. This is what technically defines a service, what it will look like, what it is capable of doing and how it's going to do it.

Standardized Service Contract
A service contract should be standardized by industry and design standards, this will greatly enhance interoperability with other vendor platforms and internal applications/services. The contract is created after the service analysis and modeling but before the implementation of the service. It's important to use contract-first design to avoid any dependencies from the contract on a specific implementation or technology. The service implementation and consumers must depend on the contract but not the other way around.

Contents
The contract will contain the following technical "documents" (not necessarily human readable documents):
- service definition, this contains the technical details of the service and its capabilities (headers, methods...)
- data definitions, this shows what the exchanged data will look like

When implementing the services as Web Services this will correspond to WSDL and XSD respectivelay. Besides these documents you might also have policy definitions when using Wew Services (WS-Policy) to enforce security or other enterprise policies.

Besides the technical documents there can also be other (non-technical) documents included in the contract such as an SLA.

The above documents can all be created independently from each other. Data and policy definitions can and should be used by different services when appropriate. This will greatly enhance the interoperability between applications and services, if different services in the enterprise use the same data but use different definitions you'll have to make data transformation and integration efforts, this is exactly what SOA wants to avoid.

Governance
The governance is also important to contracts, someone must "own" the contract and preferably not by a specific project. This is necessary to have a successful evolution of the service an to avoid that one party can make breaking changes to the contract.

Friday 15 January 2010

Stored Procedure Performance

This is just a quick tip/workaround for performance issues with stored procedures in SQL Server.

I had a fairly complex SP, actually just a SELECT with calculations, joins and outer applies, that had several parameters of different types (uniqueidentifier, varchar, datetime) that were used in the WHERE clause and passed to functions. This SP took more than 1 minute to complete but when I extracted the SELECT statement form the SP and ran it in SQL Server Management Studio it took just 3 seconds. This is quite a big difference to do the exact same thing, no?

Some time ago I read something about SQL Server doing some kind of parameter checking in SP's and this could cause a performance issue. So I tried the workaround that was mentioned there: declare new variables inside your SP, asign the values of the parameters to those variables and then use those variables in the rest of the SP. Lo and behold, my SP was finished in 3 seconds. 

I don't exactly understand what is going on here, if anybody knows the details don't hesitate to tell me.

Monday 4 January 2010

Scheduled exam S90.01

I just scheduled my first soaschool.com exam for December 30, just in time to keep on track with my planning to do one exam this year :-)

I've read the book SOA: Principles of Service Design completely, read the self-study material and I tried the sample questions. Until D-day I'll probably listen to the the CD's with podcasts and review the most important chapters of the book that concern the first exam.

Once I took the exam I'll let you know what it was like.

UPDATE: Because the exam center unexpectedly had to close last week I was forced to reschedule my exam to January 21.

Wednesday 4 November 2009

WCSF and VS2010

Guidance Automation isn't supported yet in Visual Studio 2010 beta 2 and this sucks (my apologies for using this word).

In a project we're currently working on we're using Entity Framework and the Web Client Software Factory and I would really like to use the new EF features in VS2010 beta 2 (it does have a go-live license) but also keep using WCSF and without GAX/GAT support this aint gonna happen.

But as always in IT there might be a workaround, I'll be extracting the project templates of WCSF (have a look in the install directory to find them) and adding them to the project templates of Visual Studio.

I'll keep you informed of my success or failure.

Thursday 15 October 2009

Oslo Articles

From DSLs and Models to “Quadrant” using “Oslo” May CTP

"M" In a Nutshell

Modeling as Expressed in Code

What Exactly Does One Do With “Oslo”?

MGraph Visualizer Plug-in for Intellipad!

Intellipad Team Blog

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