A Netcompany guest lecture on Service Oriented Architecture given to the Advanced Computer Systems class, the Computer Science department, University of Copenhagen (DIKU).

1. SERVICE ORIENTED ARCHITECTURE
WHAT IS IT AND WHAT IS IT GOOD FOR?
N E T C O M PA N Y L E C T U R E S E R I E S
2 0 1 5

2. R AS M U S R O S E N Q V I S T P E T E R S E N

3. (Dr.) Rasmus Rosenqvist Petersen
Consultant
Netcompany since August 2015
(Ph.d. fra Syddansk Universitet, og senest 3 år i Cambridge, England)
Sector: Unions software
Technologies: Java/JEE and Microsoft .NET

4. • Approx. 700+ consultants
– M.Sc. or Ph.D. typically from DTU, DIKU, ITU, ÅU, AAU, SDU
– Excel academically
• Offices in Copenhagen (HQ), Aarhus, Aalborg, Odense and Warszawa
• We deliver business-critical IT solutions
– Systems integration and SOA
– Portals
– Business applications
– Application and Facility Management
• Our customers include
– Financials Nordea, Saxo Bank, Letpension, PFA pension, FORCA, AP Pension
– Government KOMBIT, SKAT, Økonomistyrelsen, Undervisningsministeriet
– Industry Carlsberg, Dong Energy, Pandora
– Commerce Novozymes, Danmarks Apotekerforening
– Media JP/Politikens Hus, Aller
– Membership organizations IDA, HK, Dansk Erhverv
– Telco Telenor, TDC, Telmore
ABOUT NETCOMPANY

5. WHAT I WILL TALK ABOUT
SOA:
• SOA Concepts
• Describing a Service
• Designing Services
Mixing in
• A few cases with questions :-)

6. READY?

7. S E R V I C E O R I E N T E D A R C H I T E C T U R E

8. 1
S O A C O N C E P T S

9. Contrac t -based
L o o s e c o u p l i n g
Abs tr ac tion Reusability
AUTONOMY
Discoverability
STATELESSN ESS

10. T H E H Y P E C Y C L E

11. W H A T H A P P E N E D A F T E R 2 0 0 9 ?

12. FIRST
SOA isn’t a technology.

13. SECOND
SOA isn’t new.
SOA rests on centuries old principles.
…yes, centuries!

16. B U S I N E S S S E R V I C E S
R E C E P T I O N
F I N A N C E
A C C O U N T I N G A R C H I V E
S A L E S
A D M I N I S T R A T I O N

17. Business case:
University of Copenhagen
• What are the products?
• What are the business services?
• (think in terms of service areas and units)
R E C E P T I O N
F I N A N C E
A C C O U N T I N G A R C H I V E
S A L E S
A D M I N I S T R A T I O N

18. B U S I N E S S S E R V I C E S
ADMINIS
TRATION
SALES
ACCOUN
TING
ARCHIV
E
FINANCE
RECEPTI
ON

19. D E P E N D E N C I E S
SALES ACCOUNTING
Open Account

20. D E P E N D E N C I E S
ADMINISTRATION
SALES
ACCOUNTING
ARCHIVE
FINANCE
RECEPTION

21. S E R V I C E D E S I G N P R I N C I P L E S

22. S E R V I C E D E S I G N P R I N C I P L E S
S O U N D B U S I N E S S P R I N C I P L E S

23. S O A
ADMINISTRATION
SALES
ACCOUNTING
ARCHIVE
FINANCE
RECEPTION
MODEL

24. Case:
EFI
What
is
EFI?

25. Case: EFI
• 1.000.000.000 DKK investment lost
• Accenture: ”The worlds most complex system for tax debt
recovery” – if it had worked.
• No requirements specification (400 out of typically 5000)
• EFI tightly coupled to other system, DMI
• Two suppliers, delivering the two systems, as separate
projects
• Better to deal with two monopolies than one? No!
• SOA was used to tie the two systems together
• Why was that problematic?
http://www.version2.dk/artikel/derfor-gik-det-galt-efi-systemet-412139

26. THIRD
SOA isn’t a dogma

27. THIRD
SOA isn’t a dogma

28. S O A M A N I F E S T O
www.soa-manifesto.org
P R I O R I T I E S
Business value over technical strategy
Strategic goals over project-specific benefits
Intrinsic interoperability over custom integration
Shared services over specific-purpose implementations
Flexibility over optimization
Evolutionary refinement over pursuit of initial perfection
G U I D I N G P R I N C I P L E S
Respect the social and power structure of the organization. Recognize that SOA ultimately demands change on many
levels. The scope of SOA adoption can vary. Keep efforts manageable and within meaningful boundaries. Products and
standards alone will neither give you SOA nor apply the service orientation paradigm for you. SOA can be realized
through a variety of technologies and standards. Establish a uniform set of enterprise standards and policies …
D E F I N I T I O N

29. 2
D E S C R I B I N G A S E R V I C E

30. ...a client who satisfies all the constraints
listed is entitled to the benefits. This is the
No Hidden Clause rule.
The No Hidden Clauses principle does not
prevent us from including references,
implicit or explicit, to rules not physical part
of the contract.
Computer, Vol. 25, No. 10. (1992), pp. 40-51.
A contract is a common agreement
with benefits for all participants.
The Beatles’ first contract
A more recent contract
What is a contract?

31. A real world example
Domain model from customer
Service description from customer
XML type definition
Java service implementation stub

32. Complete vs loose contract
A complete contract
Parts of the contract differ in degree of
detail/specificity. From more to less detail:
• Security model, infrastructure
• Input / output complex types
• Simpler xml types
• Normal behavior
• Restrictions between optional elements
• Expected business exceptions
• Extreme behavior (e.g. no elements
found)
• Runtime exceptions (e.g. time out, full
disk)
• Transactional integrity
• Concurrency (even on www)
… is not always a possibility
Therefore, take great care in documenting
the decisions made during implementation:
• Record changes, and the motivation for
these
• Beware of other usages of type
• Detailed behavior in service description.
• Restrictions between optional elements
• Reuse exception types across services
• Agree on common pattern for services
• Wrap in reusable exception types
• Part of system architecture not service
• Concurrency (even on www)

33. “Contract first” vs “Code first”
• Higher detail level
• Code independent
• Greater Interoperability
• Built in governance
• Less detailed
• Developer oriented
• Easy to get started
• Easy to break contract
WSDL
Code
Code
Code

34. Case: contract
• Complete elements? • Looser elements?
University Government
Student
graduating
Money

35. 3
D E S I G N I N G S E R V I C E S

36. Domain models and services
• Model your data tables directly from
communication formats
• Don’t share physical types between
internal and external services.
Transformations in one system is easier
than changing two systems.
• Loose coupling of systems
• Provide a global logic domain model as
part of the contract, but leave external
physical communication types flexible.
• Be aware that reuse of types between
services is strong coupling
• Remember that services are used
together. Output will be used as input
by others.
Do’s Don'ts

37. Simple and more complex services
Keeping results in memory is a problem with large
result sets. Consider streaming services.
Two separate systems for vehicles and license
plates and a proxy service for an external
system with information about people.
Simple services for Create, Read, Update and
Delete, but what about more complex
services?
FindVehiclesWithPlateMatching(pattern) {
FindPlates(pattern)
For each plate
result +=ReadVehicle(VIN)
return result;
}
RegisterVechicleToPersonAndAssignPlate(VIN, person) {
UpdateVehicle // ad owner
GetNextAvailablePlate
UpdatePlate // add VIN
}
NotifyPoliceAboutExpiredPlates(startDate, endDate) {
GetAllExpiredPlates(startDate, endDate);
Foreach Plate
FindVehicle(VIN)
FindPersion(PersonID)
result += (Vehicle, Plate, Person)
}
Issues with concurrency and transactional integrity
“Batch job as service” with join over web service per
element and non-domain information (address).

38. CRUD, Find or Process service?
• Filtering on fields and values
• Avoid joining over services
• Behavior for not found and large
result sets.
Not all services are born alike!
Searching for entities via services
• On create, return assigned id
• Optional/required might differ in
create and read.
• Update by sending changes or
overwrite whole entity.
• Versioning on update can provide
optimistic locking
• Keep old versions on update and
delete operations
Create, Read, Update and Delete
• Sequences and available data
(order of creation)
• Avoid joining over services
• Consider asynchronous patterns
e.g. message queues
• Candidates for BPM
Processes in services
Bulk updates
• Avoid joining over services
• Let update services take a list of
elements to update

39. MESSAGE EXCHANGE PATTERNS
Consumer
Provider
S Y N C H R O N O U S A S Y N C H R O N O U S
Consumer
Provider
Consumer
Provider
Request/Response Request/Response One-way

40. Question:
Synchronous vs. asynchronous
• Positives? Negatives?
• Which is better for a service oriented
architecture?
Consumer
Provider
S Y N C H R O N O U S A S Y N C H R O N O U S
Consumer
Provider
Consumer
Provider

41. Synchronous = Poor scalability
Member Portal
CRM Service Pension Service Finance Service
Enterprise Service Bus
1
2 3 4
Wait time of 1 is the sum
of 2, 3 and 4 plus ESB
time.

42. AN EFFECIENT SOA
IS
ASYNCHRONOUS

43. S O A
I S H E R E T O
STAY!

44. T H A T ’ S A L L !

45. Q U E S T I O N S
?