SoftwareArchitectureVO/KU(707.023/707.024)...

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Service ArchitecturesSoftware Architecture VO/KU (707.023/707.024)

Roman Kern

KTI, TU Graz

2015-12-09

Roman Kern (KTI, TU Graz) Service Architectures 2015-12-09 1 / 68

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Outline

1 Web Services

2 Web Service Architectures

3 Resource Oriented Architectures

4 Service Oriented Architectures

5 Software as a Service

6 Microservices


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Section

Web ServicesService Architecture for the Web


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Web as a database

The Web we use is full of dataBook information, opinions, prices, arrival times, blogs, tags, tweets,etc.

The data is organized around a simple data model: node-link modelEach node is a data item that has a unique address and arepresentation

Representation formats are e.g. HTML, PDF,... for humans, or e.g XML,JSON for programs

Nodes can be interlinked using their unique addresses


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Web as a platform for distributed systems

The Web is full of services that allow humans and programs to use theWeb dataServices also have unique addressesThey use a particular representation for data exchange, e.g. XML,SOAP, WSDLServices follow a particular architecture that defines how services areusedProgrammers combine a number of services to achieve a desiredfunctionality and create a distributed system, e.g. mashups


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Types of services

What is the Google search engine?It is a service for querying a massive database (Web search index)

What is a given Web application?It is a service offering (remotely) a specific functionality

What is a Web site?It is a service offering specific human consumable information


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Types of services

All of these services are for usersHowever, we are interested in services for programmersSuch services provide an APIProgrammers use the API, unique addresses, representations ofservicesProgrammers follow the arch. style to integrate and combine servicesto achieve a desired functionalityWe will call this part of the Web: the programmable Web


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Kind of Things on the Programmable Web

There are numerous approaches to web services in all areasThe programmable Web is based on HTTP for data transport and inmost cases XML or JSON for data representationHowever, some services serve HTML, plain text, binary data, etc.Also, other things such as addressability or APIs are differentWe need a classification!


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Classification based on architectural design

Which operation should a service execute?This ismethod informationWhat data should bemanipulated?This is scoping information


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Method information

Question: how the client conveys its intention to the server?How does a server know a certain request is a request to retrieve somedata?Instead of a request to delete the same data?Why should the server do this instead of doing that


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Section

Web Service ArchitecturesREST &Web-Services


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Competing Architectures

Resource-Oriented Architectures (RESTful)RPC-Style Architectures (SOA)REST-RPC Hybrid Architectures


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Resource-Oriented Architectures

Resource-Oriented ArchitecturesDescriptive URLsURLs reflect the application stateInherit semantic from HTTPmethodsShould be statelessLimited by its simplicity (limited HTTPmethods, ...)


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RPC-Style Architectures

RPC - Remote Procedure CallAn RPC style service receives an envelope full of data from the clientThe service answers with a similar envelope again full of data to theclientBoth method and scoping information are inside of the envelopeHTTPmethods typically POST but sometimes also GET


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RPC-Style Architectures

The best example of the envelope format is SOAPThere exist other envelope formats like XML-RPCEvery RPC-style service defines a completely new vocabularyE.g. the way howmethod information and scoping information arerepresentedYou need another language to define the representation: e.g. WSDL


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Problems of RPC-Style Architectures

RPC implies an APIAPIs tend to enforce tight coupling of modules and systemsWe use declarative XML to describe APIsThis introduces processing overhead


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REST-RPC Hybrid Architectures

REST-RPC Hybrid ArchitecturesInherit parts from REST and RPC style architecturesUsed bymany Web Site for their API (e.g. Flickr, del.icio.us, ...)


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Section

Resource Oriented ArchitecturesTheory Behind REST


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Resource Oriented Architectures

4 defining features of ROAAddressability: the scoping information is kept in the URLUniform interface: the method information is kept in the HTTPmethodStatelessness: every HTTP request is isolated from other requestsConnectedness: you link resources into the Web of resources


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Addressability

Resources are exposed through URLs - an application exposes anumber of URLsWhen you have URLs you bookmark, cache responses, chain URLs, ...Many Web applications do not work this way, i.e. they are notaddressable, e.g. GMail


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Uniform interface

Standardized HTTPmethods: CRUD operations (Create, Retreive,Update & Delete)Two principlesSafety: GET only reads dataIdempotence: the same operation has the same effect whether youapply it once or multiple times


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Statelessness

Every request contains all necessary informationThere is no state managed on the server sideIn fact, there are two kinds of stateYou should distinguish between the application state and resourcestateApplication state lives on the clientResource state lives on the server


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Statelessness

When you use a search engine your current query and your currentpage belongs to application stateThey are different for every clientResource state is same for every client, i.e. search indexA crawler can update the search index


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Links and connectedness

Representations of resources, i.e. HTML or XMLmight have links toother resourcesAxiom for ROA services: Hypermedia as the engine of application stateThe current application state is not stored on the server as a resourcestateIt is tracked by the client as an application state and created by thepath that client takes through the Web


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For example http://www.google.com/search?q=jellyfishThe first page is the starting application stateYou have links to other application statesObvious for the humanWeb


http://www.google.com/search?q=jellyfish

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<Buckets><Bucket>

<Name>crummy.com</Name><URL>https://s3.amazonaws.com/crummy.com</URL><CreationDate>...</CreationDate>

</Bucket>...

</Buckets>

Following the link in the URL element takes the client to a newapplication stateUse links, links, and then use more links, ...


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Designing ROA

Figure out data setSplit the data set into resourcesThen, for each resourceName the resources with URLsExpose a subset of the uniform interface


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Designing ROA

Design representations accepted from the clientDesign representations served to the clientIntegrate this resource into other resources using linksConsider possible application statesConsider possible error states


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Example

Application similar google maps: maps of cities, streets, planets,...Data set: Maps, points, cities, planets, ....Resources: list of resources, individual resources, results of algorithmsapplied to the data setExample resources: the list of planets, Mars, Earth, San Francisco,Inffeldgasse, ...An algorithmic resource: a list of places that match certain criteria - allcities with more than 1million of people


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Example

Name the resources: create meaningful URLshttp://maps.example.com/Earthhttp://maps.example.com/Earth/France/Parishttp://maps.example.com/Earth/Austria/Citieshttp://maps.example.com/Earth/Germany/Cities?pop=1000000


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Example

Design representationsA representation talks about resource stateA representation links to other (application and resource) stateshttp://maps.example.com/Earth/Austria→http://maps.example.com/Earth/Austria/Citieshttp://maps.example.com/Earth/Austria/Cities→http://maps.example.com/Earth/Austria/Vienna


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Read/Write ROA systems

User accounts should be resourcesTo access these resources you need to use HTTP authenticationhttps://maps.example.com/user/rkernConnect with the previous resources: e.g. custom places on amaphttps://maps.example.com/user/rkern/Earth/Graz/Inffeldgasse/office


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Method Semantic in ROA systems

The HTTPmethod implies the semanticsUse GET to retrieve (read the content)

GET https://maps.example.com/user/rkern

Use PUT to write (modify the content)PUT https://maps.example.com/user/rkern+ Content

Use DELETE to write (remove the resource)DELETE https://maps.example.com/user/rkern

⇒ limited to the methods supported by HTTP


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REST

REST (Representational State Transfer)No strict typingTypically XML as data formatConcepts (RESTful) describes constrains: client-server, stateless,cacheable, layered system, code on demand, uniformityNowadays, REST is often used a umbrella terms for relatedarchitectures


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RESTful frameworks

Ruby on Rails with a pluginDjango in PythonRestlet in Java (http://www.restlet.org/)


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Section

Service Oriented Architectures -SOA

Technological Infrastructure


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Facts about SOA

SOA is the only thing Chuck Norris can’t kill.SOA invented the internet, and the internet was invented for SOA.The first rule of SOA is you do not talk about SOA.One person successfully described SOA completely, and immediatelydied.

Taken from: http://soafacts.com/


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Motivation for Services

Loose coupling→ separation of service and clientService has a contract and a schemaOrchestration→ a service is part of a bigger systemReuse by language independent and platform independent protocols


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Components of SOA

Components of SOAServices - basic components which provide functionalityService repository - used for discovery of servicesService bus - interconnect the components of SOAWorkflow engine - often used in SOA to orchestrate services


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Standards for Web Services

Standards are managed byTheW3C consortiumWS-I, an organisation to promote the interoperability of web services(platform independent, vendor independent)OASIS (The Organization for the Advancement of StructuredInformation Standards)

WSDL (Web Service Description/Definition Language) - XML format tospecify the operations of a serviceSOAP (Simple Object Access Protocol) - one-way, stateless protocol totransfer XML data to a single receiver (since SOAP 1.2 there can bemore receivers)


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Additional standards (of lesser importance)UDDI (Universal Description, Discovery and Integration) - registryservice for servicesSAML (Security Assertion Markup Language) - XML based frameworkfor user authentication, description of authorization dataXKMS (XML Key Management Specification) - management andregistry of public keys


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Web Services Standards Overview

innoQ Deutschland GmbH innoQ Schweiz GmbHHalskestraße 17 Gewerbestrasse 11D-40880 Ratingen CH-6330 ChamPhone +49 21 02 77 162-100 Phone +41 41 743 [email protected] · www.innoq.com

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InteroperabilityIssues

Metadata Specifications Reliability Specifications

Security Specifications TransactionSpecifications

Messaging Specifications SOAP

Management Specifications PresentationSpecifications

Messaging Specifications

WS-Notification

SOAP Message Transmission Optimization Mechanism

SOAP 1.2

SOAP 1.1

WS-Addressing – Core

WS-Addressing – WSDL Binding

WS-Addressing – SOAP Binding

WS-Topics

WS-BrokeredNotification

WS-Eventing

WS-Enumeration

WS-BaseNotification

Met

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Secu

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Metadata SpecificationsWS-Policy

WS-Discovery

WS-PolicyAttachment

WS-MetadataExchange

Universal Description, Discovery and Integration

Web Service Description Language 1.1

Web Service Description Language 2.0 Core

Web Service Description Language 2.0 SOAP Binding

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WS-Security

WS-Security: SOAP Message Security

WS-Security: Kerberos Binding

WS-Security: SAML Token Profile

WS-Security: X.509 Certificate Token Profile

WS-Security: Username Token Profile

WS-SecurityPolicy

WS-Trust

WS-Federation

WS-SecureConversation

Security Specifications

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Basic Profile1.1

WS-IFinal Specification

� Basic Profile – The Basic Profile 1.1 providesimplementation guidelines for how related set of non-proprietary Web Service specifications should be usedtogether for best interoperability.

Basic Profile1.2

WS-IWorking Group Draft

� Basic Profile – The Basic Profile 1.2 builds on Basic Profile1.1 by incorporating Basic Profile 1.1 errata, requirementsfrom Simple SOAP Binding Profile 1.0, and adding supportfor WS-Addressing and MTOM.

Basic Profile2.0


� Basic Profile – The Basic Profile 2.0 is an update of WS-IBP that includes a profile of SOAP 1.2.

Basic Security Profile1.0

WS-IBoard Approval Draft

� Basic Security Profile defines the WS-I Basic SecurityProfile 1.0, based on a set of non-proprietary Web servicesspecifications, along with clarifications and amendmentsto those specifications which promote interoperability.

REL Token Profile1.0


� REL Token Profile is based on a non-proprietary Web services specification, along with clarifications andamendments to that specification which promoteinteroperability.

SAML Token Profile1.0


� SAML Token Profile is based on a non-proprietary Web services specification, along with clarifications andamendments to that specification which promoteinteroperability.

Conformance ClaimAttachment Mechanism (CCAM)

1.0WS-I

Final Specification

� Conformance Claim Attachment Mechanism (CCAM)catalogues mechanisms that can be used to attach WS-IProfile Conformance Claims to Web services artefacts(e.g., WSDL descriptions, UDDI registries).

Reliable AsynchronousMessaging Profile (RAMP)

1.0WS-I

Working Draft

� Reliable Asynchronous Messaging Profile (RAMP) is aprofile, in the fashion of the WS-I profiles, that enables,among other things, basic B2B integration scenarios usingWeb services technologies.

� XML – Extensible MarkupLanguage is a pared-downversion of SGML, designedespecially for Webdocuments. It allows one tocreate own customized tags,enabling the definition,transmission, validation, andinterpretation of databetween applications andbetween organizations.

� XML – Extensible Markup Language is a pared-downversion of SGML, designedespecially for Webdocuments. It allows one tocreate own customized tags,enabling the definition,transmission, validation, andinterpretation of databetween applications andbetween organizations.

� Namespaces in XMLprovides a simple methodfor qualifying element andattribute names used in XMLdocuments by associatingthem with namespacesidentified by IRI references.

� XML Information Set is an abstract data set toprovide a consistent set ofdefinitions for use in otherspecifications that need torefer to the information in a well-formed XMLdocument.

� XML Schema – XMLSchema Definition Languageis an XML language fordescribing and constrainingthe content of XMLdocuments.

� XML binary OptimizedPackaging (XOP) is an XMLlanguage for describing andconstraining the content ofXML documents.

WS-Security1.1

OASISOASIS-Standard

WS-Security: Username Token Profile

1.1OASIS

Public Review Draft

� WS-Security is a communications protocol providing ameans for applying security to Web Services.

WS-Security: SOAP Message Security

1.1OASIS

Public Review Draft

� WS-Security: SOAP Message Security describesenhancements to SOAP messaging to provide messageintegrity and confidentiality. Specifically, this specificationprovides support for multiple security token formats, trustdomains, signature formats and encryption technologies.The token formats and semantics for using these aredefined in the associated profile documents.

WS-Security:Kerberos Binding

1.0Microsoft, IBM, OASIS

Working Draft

WS-Security: X.509Certificate Token Profile

1.1OASIS

Public Review Draft

� WS-Security: X.509 Certificate Token Profile describesthe use of the X.509 authentication framework with theWS-Security: SOAP Message Security specification.

� WS-Security: Username Token Profile describes how a Web Service consumer can supply a Username Token as ameans of identifying the requestor by username, andoptionally using a password (or shared secret, etc.) toauthenticate that identity to the Web Service producer.

WS-SecurityPolicy1.1

IBM, Microsoft, RSA Security, VeriSign

Public Draft

� WS-SecurityPolicy defines how to describe policies related to various features defined in the WS-Security specification.

WS-TrustBEA Systems, Computer Associates, IBM, Layer 7

Technologies, Microsoft, Netegrity, Oblix,OpenNetwork, Ping Identity Corporation,

Reactivity, RSA Security, VeriSign and WestbridgeTechnology · Initial Draft

WS-Security: SAML Token Profile

1.1OASIS

Public Review Draft

� WS-Security: SAML Token Profile defines the use ofSecurity Assertion Markup Language (SAML) v1.1 assertionsin the context of WSS: SOAP Message Security includingfor the purpose of securing SOAP messages and SOAPmessage exchanges.

WS-Federation1.0

IBM, Microsoft, BEA Systems, RSA Security, and VeriSign

Initial Draft

� WS-Federation describes how to manage and broker thetrust relationships in a heterogeneous federatedenvironment including support for federated identities.

WS-SecureConversationBEA Systems, Computer Associates, IBM,

Layer 7 Technologies, Microsoft, Netegrity,Oblix, OpenNetwork,

Ping Identity Corporation, Reactivity, RSA Security, VeriSign and Westbridge

Technology ·Public Draft

� WS-SecureConversation specifies how to manage andauthenticate message exchanges between parties includingsecurity context exchange and establishing and deriving session keys.

WS-PolicyAssertions1.1

BEA Systems, IBM, Microsoft, SAP

Public Draft

WS-Policy1.5

W3CWorking Draft

WS-PolicyAttachment1.2

W3CW3C Member Submission

WS-DiscoveryMicrosoft, BEA Systems, Canon,

Intel and webMethodsDraft

WS-MetadataExchange1.1

BEA Systems, Computer Associates, IBM, Microsoft, SAP, Sun Microsystems and

webMethodsPublic Draft

� WS-Policy describes the capabilities and constraints of the policies on intermediaries and endpoints (e.g. businessrules, required security tokens, supported encryptionalgorithms, privacy rules).

� WS-PolicyAssertions provides an initial set of assertionsto address some common needs of Web Servicesapplications.

� WS-PolicyAttachment defines two general-purposemechanisms for associating policies with the subjects towhich they apply; the policies may be defined as part of existing metadata about the subject or the policies may be defined independently and associated through an external binding to the subject.

� WS-Discovery defines a multicast discovery protocol fordynamic discovery of services on ad-hoc and managednetworks.

� WS-MetadataExchange enables a service to providemetadata to others through a Web services interface. Givenonly a reference to a Web service, a user can access a set of WSDL /SOAP operations to retrieve the metadata thatdescribes the service.

Universal Description,Discovery and Integration (UDDI)

3.0.2OASIS

OASIS-Standard

� Universal Description, Discovery and Integration (UDDI)defines a set of services supporting the description and discovery of businesses, organizations, and other Webservices providers, the Web services they make available,and the technical interfaces which may be used to accessthose services.

Management Of Web Services (WSDM-MOWS)

1.0OASIS

OASIS-Standard

WS-ManagementAMD, Dell, Intel, Microsoft and Sun

MicrosystemsPublished Specification

Management Using WebServices (WSDM-MUWS)

1.0OASIS

OASIS-StandardWeb Services for Remote

Portlets (WSRP)2.0

OASISCommittee Draft

� Web Service Distributed Management: Management OfWeb Services (WSDM-MOWS) addresses management ofthe components that form the network, the Web servicesendpoints, using Web services protocols.

� WS-Management describes a general SOAP-basedprotocol for managing systems such as PCs, servers,devices, Web services and other applications, and othermanageable entities.

Service Modeling LanguageIBM, BEA, BMC, Cisco, Dell, HP, Intel,

Microsoft, SunDraft Specification

� Servcie Modeling Language (SML) is used to modelcomplex IT services and systems, including their structure,constraints, policies, and best practices.

� Web Service Distributed Management: Management UsingWeb Services (WSDM-MUWS) defines how an IT resourceconnected to a network provides manageability interfacessuch that the IT resource can be managed locally and fromremote locations using Web services technologies.

� Web Services for Remote Portlets (WSRP) defines a set of interfaces and related semantics which standardizeinteractions with components providing user-facingmarkup, including the processing of user interactions withthat markup.

Web Service DescriptionLanguage 2.0 Core

2.0W3C

Candidate Recommendation

Web Service DescriptionLanguage 1.1

1.1W3CNote

Web Service DescriptionLanguage 2.0 SOAP Binding

2.0W3C · Working Draft

� WS-Business Activity provides the definition of the business activitycoordination type that is to be used with the extensible coordinationframework described in the WS-Coordination specification.

WS-Coordination1.1

OASISWorking Draft

� WS-Atomic Transaction defines protocols that enable existingtransaction processing systems to wrap their proprietary protocolsand interoperate across different hardware and software vendors.

� WS-Coordination describes an extensible framework for providingprotocols that coordinate the actions of distributed applications.

WS-Composite ApplicationFramework (WS-CAF)

1.0 · Arjuna Technologies, Fujitsu, IONA,Oracle and Sun Microsystems

Committee Specification� WS-Composite Application Framework (WS-CAF) is a

collection of three specifications aimed at solving problemsthat arise when multiple Web Services are used in combina-tion. It proposes standard, interoperable mechanisms formanaging shared context and ensuring business processesachieve predictable results and recovery from failure.

WS-Context (WS-CTX)1.0

Arjuna Technologies, Fujitsu, IONA, Oracleand Sun Microsystems

Committee Draft

� WS-Context (WS-CTX) is intended as a lightweight mechanismfor allowing multiple Web Services to share a common context.

WS-Coordination Framework (WS-CF)


Committee Draft� WS-Coordination Framework (WS-CF) allows the

management and coordination in a Web Services interactionof a number of activities related to an overall application.

WS-Transaction Management (WS-TXM)


Committee Draft� WS-Transaction Management (WS-TXM) defines a core infrastructure

service consisting of a Transaction Service for Web Services.

WS-Business Activity1.1

OASISWorking Draft

WS-Atomic Transaction1.1


ResourceSpecifications

SOAP Message Transmission Optimization

Mechanism (MTOM)1.0 · W3C

Recommendation

SOAP1.2

W3CRecommendation

SOAP1.1

W3CNote

XML 1.11.1

W3CRecommendation

XML 1.01.0

W3CRecommendation

Namespaces in XML1.1

W3CRecommendation

XML Information Set1.0

W3CRecommendation

XML Schema1.1

W3CWorking Draft

XML binary OptimizedPackaging (XOP)

1.0W3C

Recommendation

� Describing Media Contentof Binary Data in XML(DMCBDX) specifies how toindicate the content-typeassociated with binaryelement content in an XMLdocument and to specify, inXML Schema, the expectedcontent-type(s) associatedwith binary elementcontent.

Describing Media Contentof Binary Data in XML

(DMCBDX)W3CNote

XML Specifications

� WS-Trust describes a framework for trust models that enablesWeb Services to securely interoperate. It uses WS-Security basemechanisms and defines additional primitives and extensionsfor security token exchange to enable the issuance anddissemination of credentials within different trust domains.

� WS-Security: Kerberos Binding defines how to encodeKerberos tickets and attach them to SOAP messages. Aswell, it specifies how to add signatures and encryption to theSOAP message, in accordance with WS-Security, which uses and references the Kerberos tokens.

WS-Addressing – Core1.0

W3CRecommendation

WS-EventingW3C

Public Draft

� WS-Addressing – Coreprovides transport-neutralmechanisms to addressWeb services and messages.This specification definesXML elements to identifyWeb service endpoints andto secure end-to-endendpoint identification inmessages.

WS-Addressing – WSDLBinding

1.0W3C

Candidate Recommendation

� WS-Addressing – WSDLBinding defines how theabstract properties definedin Web Services Addressing– Core are described usingWSDL.

WS-Addressing – SOAP Binding

1.0W3C

Recommendation

� WS-Addressing – SOAPBinding provides transport-neutral mechanisms toaddress Web services andmessages.

� WS-BaseNotificationstandardizes the terminology,concepts, operations, WSDLand XML needed to expressthe basic roles involved inWeb services publish andsubscribe for notificationmessage exchange.

WS-EnumerationSystinet, Microsoft, Sonic Software, BEA

Systems and Computer Associates

Public Draft

� WS-Enumeration describes a general SOAP-basedprotocol for enumerating a sequence of XMLelements that is suitablefor traversing logs, messagequeues, or other linearinformation models.

WS-Notification1.3

OASISOASIS-Standard

� WS-Notification is afamily of related whitepapers and specificationsthat define a standard Web services approach tonotification using a topic-based publish/subscribepattern.

WS-BaseNotification1.3

OASISOASIS-Standard

� WS-Eventing defines abaseline set of operationsthat allow Web services toprovide asynchronousnotifications to interestedparties.

WS-Topics1.3

OASISOASIS-Standard

� WS-Topics defines threetopic expression dialectsthat can be used as sub-scription expressions insubscribe request messagesand other parts of the WS-Notification system.

WS-BrokeredNotification1.3

OASISOASIS-Standard

� WS-BrokeredNotificationdefines the interface forthe NotificationBroker. A NotificationBroker is anintermediary, which, amongother things, allowspublication of messagesfrom entities that are notthemselves service providers.

� SOAP MessageTransmissionOptimizationMechanismdescribes anabstract feature foroptimizing thetransmission and/orwire format of aSOAP message.

� SOAP is a lightweight,XML-based protocol forexchange of informationin a decentralized,distributed environment.

WS-PolicyAssertions

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Reliability SpecificationsWS-ReliableMessaging

WS-Reliability

WS-Reliable Messaging Policy Assertion

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Resource SpecificationsWeb Service Resource Framework

WS-BaseFaults

WS-ResourceLifetime

WS-Transfer

Resource Representation SOAP Header Block (RRSHB)

WS-ServiceGroup

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WS-ResourceProperties

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Presentation SpecificationsWeb Services for Remote Portlets

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Management Specifications

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WS-Management

Management Of Web Services

Management Using Web Services

Service Modeling Language

Business Process Specifications

WS-Choreography Model Overview

Web Service Choreography Description Language

Web Service Choreography Interface

Business Process Management Language

Business Process Execution Language for Web Serv. 2.0

XML Process Definition Language

Business Process Execution Language for Web Services

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Transaction Specifications

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WS-Composite Application Framework

WS-Transaction Management

WS-Context

WS-Coordination Framework

WS-Business Activity

WS-Atomic Transaction

WS-Coordination

Standards BodiesThe Organization for the Advancement of Structured Information Standards (OASIS) is a not-for-profit, international consortium

that drives the development, convergence, and adoption of e-business standards. Theconsortium produces more Web services standards than any other organization along with stan-dards for security, e-business, and standardization efforts in the public sector and for applica-tion-specific markets. Founded in 1993, OASIS has more than 4,000 participants representingover 600 organizations and individual members in 100 countries.

The World Wide Web Consortium (W3C) was created in October 1994 to lead the World Wide Web to its full potential by developing common protocols that promoteits evolution and ensure its interoperability. W3C has over 350 Member organiza-

tions from all over the world and has earned international recognition for its contributions to thegrowth of the Web. W3C is designing the infrastructure, and defining the architecture and the coretechnologies for Web services. In September 2000, W3C started the XML Protocol Activity to addressthe need for an XML-based protocol for application-to-application messaging. In January 2002, theWeb Services Activity was launched, subsuming the XML Protocol Activity and extending its scope.

The Web Services Interoperability Organization (WS-I) is an open industry organization chartered to promote Web services interoperability across platforms,

operating systems and programming languages. The organization’s diverse community of Webservices leaders helps customers to develop interoperable Web services by providing guidance,recommended practices and supporting resources. Specifically, WS-I creates, promotes andsupports generic protocols for the interoperable exchange of messages between Web services.

The Internet Engineering Task Force (IETF) is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet.

Attachments Profile1.0

WS-IFinal Specification

� Attachments Profile – The Attachment Profile 1.0complements the Basic Profile 1.1 to add support for interoperable SOAP Messages with attachments-basedWeb Services.

Simple SOAP Binding Profile

1.0WS-I

Final Specification

� Simple SOAP Binding Profile – The Simple SOAP BindingProfile consists of those Basic Profile 1.0 requirementsrelated to the serialization of the envelope and itsrepresentation in the message.

Business Process ExecutionLanguage for Web Services 1.1

(BPEL4WS) · 1.1 · BEA Systems, IBM,Microsoft, SAP,

Siebel Systems · OASIS-Standard

� WS-Choreography Model Overview defines the formatand structure of the (SOAP) messages that are exchanged,and the sequence and conditions in which the messagesare exchanged.

� Business Process Execution Language for Web Services1.1(BPEL4WS) provides a language for the formalspecification of business processes and business interactionprotocols using Web Services.

� Web Service Choreography Interface (WSCI) describeshow Web Service operations can be choreographed in thecontext of a message exchange in which the Web Serviceparticipates.

WS-Choreography ModelOverview

1.0 · W3CWorking Draft

Web Service ChoreographyInterface

(WSCI) · 1.0 · W3CSun Microsystems, SAP, BEA Systems

and Intalio · Note

Business Process Specifications

Business Process ExecutionLanguage for Web Services 2.0

(BPEL4WS) · 2.0OASIS, BEA Systems, IBM, Microsoft, SAP,

Siebel Systems · Committee Draft

� Business Process Execution Language for Web Services2.0 (BPEL4WS) provides a language for the formalspecification of business processes and business interactionprotocols using Web Services.

� Business Process Management Language (BPML)provides a meta-language for expressing businessprocesses and supporting entities.

Business Process ManagementLanguage (BPML)

1.1BPMI.org

Final Draft

� Web Service Choreography Description Language(CDL4WS) is to specify a declarative, XML based languagethat defines from a global viewpoint the common andcomplementary observable behaviour, where messageexchanges occur, and when the jointly agreed orderingrules are satisfied.

Web Service ChoreographyDescription Language

(CDL4WS) · 1.0 · W3CCandidate Recommendation

� XML Process Definition Language (XPDL) provides anXML file format that can be used to interchange processmodels between tools.

XML Process DefinitionLanguage (XPDL)

2.0Final

WS-ReliableMessaging1.1


� WS-ReliableMessaging describes a protocol that allowsWeb services to communicate reliable in the presence ofsoftware component, system, or network failures. It definesa SOAP binding that is required for interoperability.

WS-Reliability1.1

OASISOASIS-Standard

� WS-Reliability is a SOAP-based protocol for exchangingSOAP messages with guaranteed delivery, no duplicates,and guaranteed message ordering. WS-Reliability isdefined as SOAP header extensions and is independent ofthe underlying protocol. This specification contains abinding to HTTP.

WS-Reliable Messaging Policy Assertion (WS-RM Policy)

1.1OASIS

Committee Draft

� Web Services ReliableMessaging Policy Assertion(WS-RM Policy) describes a domain-specific policy assertionfor WS-ReliableMessaging that that can be specified withina policy alternative as defined in WS-Policy Framework.

� Web Service Description Language 2.0 Core is an XML-based language for describing Web services and how toaccess them. It specifies the location of the service and theoperations (or methods) the service exposes.

� Web Service Description Language 1.1 is an XML-basedlanguage for describing Web services and how to accessthem. It specifies the location of the service and theoperations (or methods) the service exposes.

� Web Service Description Language SOAP Bindingdescribes the concrete details for using WSDL 2.0 inconjunction with SOAP 1.1 protocol.

WS-BaseFaults (WSRF)1.2

OASISWorking Draft

Web Services Resource Framework (WSRF)

1.2OASIS

OASIS-Standard

WS-ServiceGroup (WSRF)1.2

OASISWorking Draft

� WS-BaseFaults (WSRF) defines a base set of informationthat may appear in fault messages. WS-BaseFaults defines anXML schema type for base faults, along with rules for howthis base fault type is used and extended by Web Services.

� Web Services Resource Framework (WSRF) defines a family ofspecifications for accessing stateful resources using Web Services.

� WS-ServiceGroup (WSRF) defines a means by which WebServices and WS-Resources can be aggregated or groupedtogether for a domain specific purpose.

WS-ResourceProperties1.2

OASISWorking Draft

� WS-ResourceProperties specifies the means by which thedefinition of the properties of a WS-Resource may be declaredas part of the Web Service interface. The declaration of theWS-Resource properties represents a projection of or a viewon the WS-Resource state.

� WS-ResourceLifetime is to standardize the terminology,concepts, message exchanges, WSDL and XML needed tomonitor the lifetime of, and destroy WS-Resources.Additionally, it defines resource properties that may be usedto inspect and monitor the lifetime of a WS-Resource.

� WS-Transfer describes a general SOAP-based protocol foraccessing XML representations of Web service-based resources.

WS-ResourceLifetime1.2

OASISWorking Draft

WS-TransferW3C

W3C Member Submission

Resource RepresentationSOAP Header Block (RRSHB)

W3CRecommendation

� Resource Representation SOAP Header Block (RRSHB)complements MTOM by defining mechanisms fordescribing and conveying non-XML resource representationsin a SOAP 1.2 message.

http://www.innoq.com/resources/ws-standards-poster/


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Example of WSDL & SOAP

Definition of an operation: GetUserDataThe operation has an input and an outputThe input is defined via GetUserDataRequestThe output is defined via GetUserDataResponse


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Example of WSDL

<wsdl><wsdl:operation name="GetUserData">

<wsdl:input message="es:GetUserDataRequest"/><wsdl:output message="es:GetUserDataResponse"/>

</wsdl:operation><xsd:element name="GetUserDataRequest">

<xsd:complexType><xsd:sequence>

<xsd:element name="username" type="string"/><xsd:element name="role" type="string"/>

</xsd:sequence></xsd:complexType>

</xsd:element><xsd:element name="GetUserDataResponse">

<xsd:complexType><xsd:all>

<xsd:element name="email" type="string"/></xsd:all>

</xsd:complexType></xsd:element>

<wsdl>


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Example of SOAP

<soap:Envelope><soap:Body xmlns:m="http://www.example.org/userdata">

<m:GetUserData><m:email>[email protected]</m:email>

</m:GetUserData></soap:Body>

</soap:Envelope>


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Orchestration of Services

How are services interconnected with each other?Applications are realized by a combination of servicesOrchestration takes care which services interact and whenControl flow can be automated via workflow enginesShould help reuse by loose coupling and flexibility


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Binding of Services

Development-time binding vs. runtime bindingDevelopment-time binding is far simplerThe services, their API and address are fixed during development timeRuntime binding is more complexThe exact services and addresses are found during runtimeLookup by service name often the best approach


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Discovery of Services

How do I find the service for my needs?UDDI aimed at a lookup service for businesses, organisation andservicesUDDI as yellow pages for web servicesNo widespread useShould help addressability


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Service Types

Typical service (component) types in SOA systems:Application frontend - typically not a service, initiate operation andreceive resultsBasic services - they build the foundationIntermediary services - adapters and facades to add functionality,typically statelessProcess centric services - implement the business logic, typicallymanage the process statePublic services - for integration, higher level functionality


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SOA and Software Architecture

SOA aims to decouple the system from the software architectureNo alignment between the system layers and the service layers

system layers: browser, application server, web server, operation systemservice layers: application, process, intermediary, basic


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Example: Simple SOA Architecture

In the most simple case the SOA architecture consists of two layersThe application layer, which uses the basic servicesThe layer for the basic servicesFor example: A web site of an airline


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Example: Simple SOA Architecture


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Facade Pattern

Intermediary services often serve as facade for basic servicesThey aggregate the functionalityExample for a n-tier architecture


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Example: Facade Pattern


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Process-centric Services

Optional component in SOA systemsProcess-centric services encapsulate process logic and applicationstateAn application frontendmay delegate the process control to such acomponentAdvantage: reuse when the process-centric services is shared bymultiple clientsDisadvantage: more complex system, process control might be splitinto multiple components


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Example: Process-centric Services


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Best practices

Limit access to dataHave a single service to manage the dataFor example, instead of two services with two interfaces provide asingle service with two interfaces


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Example of Cross-Cutting Concerns

Example of how to tackle cross-cutting concerns with SOA:Logging of information, warning, failures, etc.⇒ Log locally, but view globallyEach service uses a local logging functionality, logs are thenaggregated


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Security in SOA

Additional security considerations for servicesHow to protected against attacks?Trusted domain vs. securing every serviceTrust domains usually in use for base servicesUse unified security framework


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Section

SaaSSoftware as a Service


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SaaS

SaaS IdeaAn application is made available via a service interface. The application ishosted by a service provider via the internet (commonly referred to as theCloud).

If the service is hosted within an organisation, it is called “on premises software”.


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SaaS

Properties of SaaSAdvantages: One has not worry about application deployment,maintainance, securityDisadvantages: Loose control over the application, the serviceprovider may conduct unwanted changesThe billing is often done on per request basis and low entry pricesExamples: Salesforce.com, Sensium.io


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Section

MicroservicesArchitecture for Enterprise Applications


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Motivation for Microservices

Traditional service architecturesServices has often been used to decouple the UI from the servercomponentsAnd services have been envisioned to provide high level functionality

MicroservicesExpose finer grained functionalities in form of servicesServices are developed and deployed independently from each other


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Microservices Advantages

Advantages of microservicesSmaller services

Easier to maintain and better learnability

Deployment can be conducted independently for each serviceMore explicit separation of concernsServices can be developed using different technology stacksImproved fault isolationImplementations of services can be swapped


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Microservices Disadvantages

Disadvantages of microservicesComplexity inherited due to distributed system

Transaction support (very complex or not possible)Use-cases spawning multiple service are complexHigher latency due to communication overheadHigher risk or errors due to distributed natureMore computational resources needed (e.g. more memory)

Testing is more demandingDeployment needs to be conducted for each service

Deployment of multiple services need to be necessary at the same time


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Microservices Challenges

Challenges of microservicesWhen does it make sense to switch frommonolithic to microservices

For small systems the overheadmight be too bigIn case the system grows overtime, it need to be already be designed toallow being split into individual parts/services

Level of granularity of services (might not be clear how to partition)


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The EndNext: Architectural styles I


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