Chris Riley S O A Modeling

SOA Workshop

An Introduction to Service Modeling

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Five titles currently in

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A Note About

SOAMethodology.com

Before we begin:

The following description of Service Modeling is part of a

mainstream SOA methodology that is further explained at

www.soamethodology.com.

This mainstream methodology is not proprietary and does not compete

with other approaches. It is the result of on-going industry research that

provides a balanced blend of the most common, proven, and mature

approaches currently in use.

For any given IT enterprise, this methodology is considered a starting

point only, and almost always requires further customization.

The purpose of this mainstream methodology is to raise key

considerations for the delivery of SOA projects and specific project

lifecycle stages.


Service Delivery Terminology

Let’s first establish some common terms:

• “Service Candidate”

• “Service Inventory Blueprint”

• “Service-Oriented Analysis”

• “Service Modeling”

• “Service-Oriented Design”

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SOA Projects

SOA projects introduce new considerations and

tend to augment traditional the project lifecycle.

Specifically, SOA projects require:

• more up-front analysis effort

• closer collaboration between business and

technology experts

• a careful prioritization of tactical and strategic

needs


Up-Front Analysis

• An SOA project is often actually a service delivery

project that is part of a larger SOA initiative.

• The scope of the initiative and the size of the target

service inventory tend to determine the amount of

up-front effort.

• More up-front analysis results in a better defined

blueprint which results in a better quality inventory of

services.

• This up-front analysis effort is carried out iteratively as

part of the Inventory Analysis Cycle.

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Up-Front Analysis

The Inventory Analysis

process is comprised of

an iterative cycle during

which the service

inventory blueprint is

incrementally defined

as a result of repeated

iterations of steps that

include the service-

oriented analysis.


Analysis Collaboration

• To carry out the up-front analysis work requires the

involvement of business analysis and technology

architecture experts.

• Business expertise is needed for the definition of

business service abstraction layers.

• Technology architecture expertise is needed for all

services.

• This form of collaboration establishes the basis for the

service-oriented analysis process.

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Analysis Collaboration

How analysts and architects work together in

SOA projects is a departure from traditional projects.


SOA Project Delivery

Prior to commencing with the analysis process, a project approach needs to be chosen to best organize the overall delivery lifecycle.

Three common delivery approaches have emerged:

- top-down

- bottom-up

- meet-in-the-middle

Of these, some extent of top-down delivery is usually required to incorporate meaningful levels of inventory and service analysis.

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Tactical vs. Strategic

• In service delivery projects there is a constant

need to balance pressing tactical requirements

against preferred strategic requirements.

• Tactical refers to the fulfillment of short-term,

immediate requirements (which are usually

specific to the organization).

• Strategic refers the fulfillment of long-term goals

associated with SOA and service-oriented

computing.


Tactical vs. Strategic

• The greater the priority of tactical requirements,

generally the less time there is for up-front analysis

effort. This leads to a tendency to apply more of a

bottom-up approach.

• The greater the priority of strategic goals, the more is

invested in up-front analysis stages, which

corresponds with a top-down approach.

• The meet-in-the-middle delivery approach attempts

to provide a compromise by allowing a top-down

analysis to occur while delivering services that are

later re-aligned.

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Service Delivery & Governance

Up-front analysis as

part of a top-down

effort reduces the

eventual

governance

burden.

The bottom-up

approach results in

less up-front

impact, but defers

burden to the

governance phase.


Service-Oriented Analysis

• A service-oriented analysis is a formal process completed jointly by business analysts and technology architects.

• Service modeling is a sub-process of service-oriented analysis that produces conceptual service definitions called service candidates.

• The subsequent service-oriented design process uses these candidates as a starting point and then shapes them into physical service services.

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Service-Oriented Analysis

• The typical scope of a service-oriented analysis

is one business process.

• In a top-down delivery, the service-oriented

analysis process is carried out repeatedly as part

of the Inventory Analysis Cycle.

• Each iteration is focused on analyzing a different

business process.


Service-Oriented AnalysisA generic service-oriented

analysis process that can be

further customized.

In a nutshell, it represents a

parent process comprised of

two information gathering steps

and a detailed service modeling

sub-process.

Business logic is essentially

decomposed into preliminary

service operation candidates

that are then grouped into

logical contexts that represent

conceptual services called

service candidates.

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Service Modeling

• Service modeling is essentially a process by which proposed capabilities are identified and grouped into proposed services.

• It is therefore important to continually remind ourselves that we are not actually implementing a physical design at this stage.

• Using the terms “service candidate”, “service operation candidate”, and “service composition candidate” clearly communicates this.


Service ModelingA generic

service

modeling

process that

can be

further

customized.

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Logic Types

There are four fundamental service logic types that

allow you to choose and position (and customize)

service models and service abstraction layers as

part of a service inventory blueprint:

• business

• utility

• agnostic

• non-agnostic


Service Models

The following primary service models exist:

• Entity Service – Functional business context associated

with a business entity or a collection of related

business entities.

• Utility Service – Functional non-business context

associated with a related set of processing

capabilities.

• Task Service – Functional business context associated

with a specific business process. (A variation of this

service model is the Orchestrated Task Service.)

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Logic Types and Service Layers

Business

Logic

Utility

Logic

Agnostic

Logic

Non-

Agnostic

Logic

Utility

Service

Layer

X X

Entity

Service

Layer

X X

Task

Service

Layer

X X


Entity Service Definition

• An entity service is a form of business service

because it has a business-centric context.

• It derives its context from a specific business

entity (or a group of related business entities).

• Examples of business entities:

invoice

purchase order

claim

employee

customer

product

policy

benefit

vendor

partner

credit note

ledger

vehicle

site

region

zone

account

license

shipment

ingredient

asset

equipment

material

resource

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Entity Service Definition

• Entity service capabilities

provide functionality

centered around the

processing of the

information set associated

with the business entity.

• This leads to many CRUD-

style capabilities.


Utility Service Definition

• The purpose of the utility service layer is to establish services that provide functionality that addresses cross-cutting concerns.

• These types of services have a functional scope that is deliberately non-business-centric.

• They are also referred to as “application services” or “infrastructure services”.

• Utility services often encapsulate enterprise resources, such as legacy systems and databases, and expose them in unique contexts.

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Utility Service Definition

• Utility services are typically composed by parent

business services.

• Utility services are often

the most challenging

type of service to

design and evolve

because an

appropriate functional

context is difficult to

determine.

• Following are some guidelines for defining utility

service contexts.


Task Service Definition

• Task services encapsulate business logic specific to a

parent task or business process.

• A parent task represents business process logic that

spans business entities.

• Task services are intentionally non-agnostic and therefore have limited reuse potential.

• The task service definition results from the application

of the Non-Agnostic Context pattern in addition to any

further analysis steps that may be part of the overall

modeling process.

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Task Service Definition

• Task services usually act as controllers in complex

compositions, but they are ideally modeled to

participate as composition

members as well.

• Task services tend to be

more stateful than agnostic

services and almost always

expose fewer capabilities.


Service Layer Abstraction

Service layers abstract

different types of logic…

…and establish logical

domains for governance

purposes.

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Service Layer Abstraction

A typicalcomplex compositionwill span multiple layers.


Primitive Service Definition

and SOA Patterns

The primitive service definition process is carried out by

sequentially applying the following patterns:

• Service Encapsulation

• Agnostic Context Definition

• Non-Agnostic Context Definition

• Agnostic Capability Definition

• Capability Composition

• Capability Recomposition

Note that each pattern essentially corresponds to a

foundational step within service-oriented analysis and

design. For more information, see SOAPatterns.org.

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Project

Roles

SOA project roles

have common

relationships with

specific phases of

a typical SOA

project delivery

lifecycle.

Note that this

diagram does

not show the

service

governance

lifecycle.


Services and Granularity

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Contact and Resources

SOA Systems Inc. www.soasystems.com

SOA Training www.soaschool.com

SOA Certification www.soacp.com

SOA Books www.soabooks.com

SOA Magazine www.soamag.com

SOA Patterns www.soapatterns.org

Updates [email protected]

Contact [email protected]

Chris Riley S O A Modeling

Technology

Transcript of Chris Riley S O A Modeling