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COMP206

Architecture Guidelines for

Composite Applications

Volker Stiehl, SAP NetWeaver Product Management Composition

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© SAP 2008 / SAP TechEd 08 / COMP206 Page 2

Disclaimer

This presentation outlines our general product direction and should not be

relied on in making a purchase decision. This presentation is not subject to

your license agreement or any other agreement with SAP. SAP has no

obligation to pursue any course of business outlined in this presentation or to

develop or release any functionality mentioned in this presentation. This

presentation and SAP's strategy and possible future developments are

subject to change and may be changed by SAP at any time for any reasonwithout notice. This document is provided without a warranty of any kind,

either express or implied, including but not limited to, the implied warranties

of merchantability, fitness for a particular purpose, or non-infringement. SAP

assumes no responsibility for errors or omissions in this document, except if

such damages were caused by SAP intentionally or grossly negligent.

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Goal

Composite Applications require a change inthinking from an architect‘s as well as from adeveloper‘s point of view.

Learn how to successfully architect a compositeapplication and apply the principles to your ownprojects!

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1. Anatomy of composite applications

2. Patterns for the service design

3. Patterns for the service composition and business object layer

4. Patterns for the UI layer

5. Patterns for the process layer

6. Summary

Agenda

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Definition of a Composite Application

Wikipedia: A Composite Application is an application built by

combining multiple existing functions into a new application.

Extended Definition: Composite Applications are user centric applications supporting highly collaborative and dynamic

business processes which span beyond functional, system,

and organizational boundaries by using data and functions

provided as services by platforms and applications.

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Anatomy of Composite Applications

Business Objects

Local Remote

C O

M P O S I T E A P P L I C A T I O

N

CRM BW ERP Systems B A C K E N D

Workcenter

Composite Process

Role 1 Role 2

Step 1 Step 2 Step 3 Step 4

Service EnablementServices Services Services

Enterprise Service Bus

(optional)

Remote

Services

Local

Services

Business Objects,

Services

UI UI UI User Interfaces

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Example: Investment Approval Process

PurchaseRequester

• Enter requirements

External ITProvider

• Derive product from requirements,create purchase request

Business

rule

• Derive necessity for approval based oninvestment volume and country

• Ensure company policies

Purchase Approver

• Review order, approve or reject and incase of rejection add reason andpropose acceptable solution

PurchaseRequester

• Update purchase order or terminateprocess

CorporatePurchasing

• Create PO in ERP including supplierintegration

TrackChanges

• Fulfill compliance requirements

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Artifacts of a Composite Application

Storage

Local Persistency

History Data

Business

Object

History DataMaterial

Roles

Purchase Requester Purchase Approver

Process

UI

Interface

Enter Purchase

Request

Review Manager

Decision

View Purchase

Order Confirmation

Approve Purchase

Request

Service

Read Material

Details Approval

Needed

Service

Save Change

History

Create

Purchase

Order Find Material

System

SCMERP

Primary Secondary

Corporate Purchaser

Purchase

RequestPurchase Order

Investment Approval

Process

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Composite Application Design Patterns

Composite Application Design Patterns

Describe a typical problem, which regularly occurs in composite applicationdesign

Describes Best Practices on solving that problem, mostly aiming at

Consistency

Completeness

Pragmatics while keeping appropriate architecture

Design Patterns consist of

Name (Catch Phrase, e.g. Backend Abstraction Layer)

Problem Description

Solution Description

Consequences (Trade offs, use with other patterns…)

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6. Summary

Agenda

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Global Data Types I

Problem description Arbitrary definition of data types may cause

inconsistencies/redundancies for same business

semantics

unnecessary data mapping overhead

missing coverage of business semantics

Automatic web service generation based on existing artifacts

may not leverage type system capabilities (e.g. Java™

technology vs. XSD)

may cause namespace and packaging problems

are dependent on the quality of those ‗legacy‘ artifacts

may not comply with industry standards

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Global Data Types II

Solution description

Maintain a (company-) global repository of data types for your services

interfaces.

Compose your data types from core data types defined in the international

standards ISO 15000-5 and UN/CEFACT CCTS

(http://xml.coverpages.org/ni2007-04-20-a.html)

Provide tools for developers and non-developers to design and discover globaldata types

Consequences

Need for a governance process

Need for naming conventions and design documents

The repository can be extended for services and reusable UI components

based on Global Data Types

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Compensation Service I

Problem description

Enterprise Services are mostly stateless and atomic Stateless: no state is kept at service provider

(‗Backend‘) between service calls Implication: no pessimistic locking of data inBackend

Atomic: each service updating the databasedoes its own commit

No generic support for distributed ACID transactionsbetween a composite and its backends

Rollback of preceding successful calls is notpossible.


Provide a compensation service for each modifying-service operation (e.g. create reservation cancelreservation)

Success

Success

Success

Failure

Failure

Failure

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Compensation Service II

Consequences A compensation service for modifying-services may be difficult to implement or

impossible.

Service calls can trigger other business related activities, that are hard or

expensive to stop (e.g. purchase order triggers supplier involvement)

Consider also using the ‗Check Service Pattern‘

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Check Service I

Problem description (Similar to Compensation Service)Enterprise Services are stateless and atomic

There is no generic support for distributed ACID transactions between a

composite and its backends

If one modifying service in a sequence of modifying service call fails, there is

no rollback possibility


Implement a check service for each modifying service

Call it like a prepare commit in distributed transactions, i.e. as data validation

step directly preceding the modifying service (e.g. create reservation check

availability)

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Check Service II

Consequences

Successful call of check service does not guarantee that the subsequent

modifying service will also succeed.

Typically used in combination with ‗Compensation Service‗ Pattern reduce

probability that compensation call will be needed.

Process

ContextParameters

Step 1

UI

Service Service

Check Update

Step 2

Error handling

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6. Summary

Agenda

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Service Adaptation I

Problem description

Enterprise Services design is business driven, not consumer tools driven

Existing services are often too complex or not fitting the need of the

consumer in a composite application (e.g. UI, process)

Typical adaptations required

Projection of types (discarding parts by defaulting or completely omitting

them)

‗Flattening‘ nested types

filtering/sorting/truncating collections

Type ‚casts‗ (e.g. ISO 8601 timestamp to java.util.Date)

Service chaining Pass results of service A to subsequent service B

Merge/Join results of A and B

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Service Adaptation II


Implement a service adaptation layer tailoring backend services to the needs its

consumers

Use frameworks such as the Composite Application Framework (CAF),

Enterprise JavaBeans™ specification, or Spring

Strive for type re-use (i.e. leveraging parts of service types for target types)

Expose the adapted services as Web Services

Be transparent to the inner logic of the composite application

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Service Adaptation III

Claim

----------------------

- claimId- salesOrderID

- salesOrderPosition

- reason

- …

SalesOrder

---------------------- salesOrderID

- …

- …

Claim

---------------------

- claimId

- salesOrderID

- material

- reason

- …..

SalesOrderItem

---------------------

- material

- …

- …

1 n

Find Claim By ID Find Sales Order By ID

Find Claim By ID

Service Adaptation Layer

Backend

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Service Adaptation IV

Consequences

In service chains with iteration, try to parallelize service calls

Iterate on results of service A, calling service B sequentially is sub-optimal

If B doesn‘t allow for mass input data, perform calls in parallel threads

Note: if B can be changed for mass input data, it‘s the preferred option

Regarding performance, executing service adaptation in backend would beoptimal

May reduce network traffic between backend and composite

May allow for easier parallelization of calls

May allow more efficient/convenient (mass-)data processing

No hard coding of default values: expose via configuration UI

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Service Adaptation IV

Consequences

In service chains with iteration, try to parallelize service calls

Iterate on results of service A, calling service B sequentially is sub-optimal

If B doesn‘t allow for mass input data, perform calls in parallel threads

Note: if B can be changed for mass input data, it‘s the preferred option

Regarding performance, executing service adaptation in backend would beoptimal

May reduce network traffic between backend and composite

May allow for easier parallelization of calls

May allow more efficient/convenient (mass-)data processing

No hard coding of default values: expose via configuration UI

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Backend Abstraction Layer I

Problem description

A composite application should be decoupled from the backend system(s) it is

operating on during runtime.

Allow for exchange of backend system or services without modification of

‗inner‘ composite logic

Precondition: Replacement provides same business-data/-semantics

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Backend Abstraction Layer II


Define an interface fitting the needs of the inner logic of the composite.

This interface is called Backend Abstraction Layer interface or BAL

interface shortly.

The BAL interface is the stable ―contract‖ defining the expected business

functionality

all potential combinations of backend services have to fulfill the contract or

be adapted to it

Switching backend services should be a configuration task, i.e. only redirecting

a ―pointer‖ in the composite‘s customizing data.

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Backend Abstraction Layer III

Defines stable interface

Defines required business functionality

Defines behavior for error handling

Backend Abstraction Layer

Business Logic Layer

Service Adaptation

Platform independent

Service Interface

Platform independent

Service Adaptation

Platform dependent

Service Interface

Platform dependent

Service Adaptation

Platform dependent

Service Interface

Platform dependent

Switch between implementations

via Configuration

Backend Backend

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Backend Abstraction Layer IV

Consequences

By using EJBs, switching can be done by Java Naming and Directory

Interface™ (JNDI) name exchange in configuration

Within the SAP NetWeaver Composition Environment the Composite

Application Framework (CAF) fulfills these requirements

Can be used for transition from ‗legacy‘ services to Web Services, which is

especially important if service provisioning runs in parallel to compositeapplication development.

Abstraction of connectivity protocols

Abstraction of data syntax (e.g. leading zeros in return values)

Abstraction of data semantics (mapping to Global Data Types)

Note: this pattern can be combined with Service Adaptation pattern

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6. Summary

Agenda

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Object Work List I

Problem Description

The end user wants to search and retrieve business objects to be processed byhim. Based on the query results, he wants to execute further actions.


If the Object Work List is not provided by the server or a framework, create a UIfor selection criteria and a result table.

The selection criteria should support intervals, operators/wildcards, multiple

values per criteriaSupport persistency for user queries so the user does not have to re-create

them every new session.

The result table has to support features like filtering, sorting, column movingand hiding

Since user queries may take long to execute depending on selection criteria

values, query result caching should be implemented.Due to the same reason, queries should be executed asynchronously (i.e.

without blocking the UI), allowing to work with other queries while refresh isperformed.

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Object Work List II

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Object Work List II

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Object Work List III

Consequences

A similar alternative pattern is Workflow Inbox populated with work items of

the current user in a push mode (allows only filtering after population, but no

direct influence to item retrieval by the user)

Consequently, Workflow Inbox doesn‗t offer selection criteria to the user.

Workflow Inbox is the typical pattern when working process-based only (i.e.

process runtime pushes work items according to process-step – users/rolesassignments)

Object Work List is typically suitable for expert workers responsible for their

workload on their own, while the Workflow Inbox also fits to non-experts.

Other indicator for Object Work List (but no strict implication necessarily):

working with mass data

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Wizard UI

Problem descriptionSequential steps that are to be executed by one role ―in one go‖


Use a Wizard UI component in one step of the process model

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6. Summary

Agenda

D l d W it O ti I

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Delayed Write Operation I

Problem description

A service write operation is called directly from

the user interface

There is no possibility to add additional steps,

like approval or checks by other users

If the write operation succeeds and the update of

the process status fails, the process is in aninconsistent state


Store the user input in the process context and

perform the write operation in a subsequent step

Process

ContextParameters

Step 1

UI

Service Service

Check Update

Step 2

Error handling

D l d W it O ti II

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Delayed Write Operation II

Consequences Separating service calls into dedicated process steps causes additional effort,

e.g. for error handling.

Do only separate the modifying service call into a subsequent process

step; no further separations should be done (e.g. check services can be called

by UI component directly).

The service call will be repeated periodically until a success or failure message

is received by some process runtimes.

Works best in combination with idempotent services (see next slide)

Id t

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Idempotency

Idea: identify a service call uniquely, only executing it exactly once.

pass unique ID with service request message the server will process this message and cache its results on first receipt

in case of subsequent requests with same ID, cached result is returned

java.util.UUID.randomUUID() conveniently generates UUIDs

Service

Consumer

Service

Provider

Input Message

(query / request)

Return Message

(response / confirmation)

Undelivered Response

Service

Consumer

Service

Provider

Input Message

(query / request)

Return Message

(response / confirmation)

Successful Call

Service

Consumer

Service

Provider

Input Message

(query / request)

Undelivered Request

Note: Idempotency becomes less important when EOIO-messaging (e.g. WS-RM compliant) is ensured

But more sophisticated infrastructure required both on server and client

E t li d R l (R l E i ) I

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Externalized Rules (Rules Engine) I

Problem description

Business rules change more frequently than the rest of the application code

The same rule may be applied in many processes


Use a rules engine (JSR-94 compliant or proprietary implementation) that

allows central creation and management of your business rulesSeparate condition and action

The conditions should be handled by the rules engine

The actions should be defined in the process flow

The process model should not be affected by a rule modification

A d

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6. Summary

Agenda

S

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Summary

Use Composite Application Design Patterns to improvethe architecture of your applications

Use them with common sense

Adapt them to your own needs

Existing frameworks or server infrastructure may already

provide them out of the box

Recommended Reading

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Recommended Reading

Jan Rauscher, Volker Stiehl

Programmierhandbuch

SAP NetWeaver

Composition Environment

The Developer‘s Guide to the SAP

NetWeaver CompositionEnvironment

ISBN 978-3-8362-1129-1

(German)

ISBN 978-1-59229-171-7

(English)

http://www.sap-press.de/1655 (de)

http://www.sap-press.de/1671 (en)

Building Your Business with

http://www.sap-press.de/1655








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Further Information

Related Workshops/Lectures at SAP TechEd 2008

COMP101, Building Custom Applications with SAP NetWeaver CE,

Lecture

COMP164, Developing Composite Applications With SAP NetWeaver

CE, Lecture

COMP201, Deep Dive Into Real-World Composite Applications,

Lecture

COMP261, Creating Service Mashups With the SAP Composite

Application Framework, Hands-On

Related SAP Education and Certification Opportunities

http://www.sap.com/education/

SAP Public Web:

SAP Developer Network (SDN): www.sdn.sap.com/irj/sdn/nw-ce www.sdn.sap.com/irj/sdn/nw-composition

Business Process Expert (BPX) Community: www.bpx.sap.com


http://www.sdn.sap.com/irj/sdn/nw-ce

http://www.sdn.sap.com/irj/sdn/nw-composition

http://www.bpx.sap.com/

http://www.bpx.sap.com/








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