TDDD05
Component-Based Software
Web Services
Many slides by courtesy of Welf Löwe, Stig Berild, Uwe Aßmann, C. Kessler
Content:
* SOAP
* WSDL
* UDDI
* BPEL, BPMN
* Web services and Java
* Evaluation and Wrap-up
Ola Leifler, IDA, Linköpings
universitet
Recommended Reading
 Szyperski, Chapter 12.4 + 10.5.3
 W.M.P. Van der Aalst.
Don't go with the flow: Web services composition standards exposed.
IEEE Intelligent Systems, Jan/Feb 2003.
http://tmitwww.tm.tue.nl/research/patterns/download/ieeewebflow.pdf
O. Leifler, IDA, Linköpings universitet.
2
TDDD05 Component-Based Software
Service =
deployed components +
provider with infrastructure
Keyword: Service
Accounts Coop.
Amazon.com
Billing
Servicearchitecture
Citybank
UPS
Delivery
O. Leifler, IDA, Linköpings universitet.
Order processing
Creditability check
3
Payment
TDDD05 Component-Based Software
Reuse of (some) Services
Account
s
Web
Aggregate
Order acceptance
Amazon.com
Billing
Storage
Billing
Order processing
Packing
Parcel service
Checking
Delivery
O. Leifler, IDA, Linköpings universitet.
4
Bank
Payment
Creditability check TDDD05 Component-Based Software
Web Services: basic concept
Data
Operation/Process
Standards required!
O. Leifler, IDA, Linköpings universitet.
5
TDDD05 Component-Based Software
Service-Oriented Architectures (SOA)
 All software components are modeled as services
to be consumed over the network
 The focus of design is on the service’s interface
Applications are integrated at the interface (contract) level,
not at the implementation level
 Services will be published (or withdrawn) dynamically
Registry
 Services will be searched and discovered
Discovery
facility
 SOA are based on traders
CORBA with
O. Leifler, IDA, Linköpings universitet.
trader service is a SOA, albeit platform-specific
6
TDDD05 Component-Based Software
Description Framework
Revolution
Vision
Judgments
Evolution
Exists
Judgment
O. Leifler, IDA, Linköpings universitet.
Approaches
7
Components of
Web Services
TDDD05 Component-Based Software
XML
Data Exchange
+ W3C Recommendation
(standard)
+ Easy syntax for hierarchical,
structured documents
+ Widely spread, accepted
Data: XML-document
- No semantics
- Not compact / low performance
- Ongoing standardizations
Approach
Exists
O. Leifler, IDA, Linköpings universitet.
XML
8
Components of
Web Services
Message Description
TDDD05 Component-Based Software
XML Example
<treatment>
<patient insurer=“1577500” nr=‘7503100815’/>
<doctor city=“SB” nr=‘4321’/>
<service>
<mkey>1234-A</mkey>
<date>2001-01-30</date>
<diagnosis>No complications.
</diagnosis>
</service>
</treatment>
O. Leifler, IDA, Linköpings universitet.
9
TDDD05 Component-Based Software
Example:
Simple XML Schema types
<simpletype name=‘mkey’ base=‘string’>
<pattern value=‘[0-9]+(-[A-Z]+)?’/>
</simpletype>
<simpletype name=‘insurer’ base=‘integer’>
<precision value=‘7’/>
</simpletype>
<simpletype name=‘myDate’ base=‘date’>
<minInclusive value=‘2007-01-01’/>
<maxExclusive value=‘2007-04-01’/>
</simpletype>
O. Leifler, IDA, Linköpings universitet.
10
TDDD05 Component-Based Software
Example:
Complex XML Schema types
<complextype name=‘treatment’>
<element name=‘patient’ type=‘patient’/>
<choice>
<element ref=‘doctor’/>
<element ref=‘hospital’/>
</choice>
<element ref=‘service’
maxOccurs=‘unbounded’/>
</complextype>
O. Leifler, IDA, Linköpings universitet.
11
TDDD05 Component-Based Software
Example:
XML Schema Attributes
<complextype name=‘patient’ content=‘empty’>
<attribute ref =‘insurer’ use=‘required’/>
<attribute name=‘nr’ use=‘required’>
<simpletype base=‘integer’>
<precision value=‘10’/>
</simpletype>
</attribute>
<attribute name=‘since’ type=‘myDate’/>
</complextype>
O. Leifler, IDA, Linköpings universitet.
12
TDDD05 Component-Based Software
Question
 Why do people like XML?
It
is wordy
Slow
Ugly
....
 Remark: Binary XML variants are under development...
See
e.g. IEEE Computer 38(4): 16-18, April 2005
+
compression
-
portability
-
many competing standards (although W3C has adopted
EXI)
O. Leifler, IDA, Linköpings universitet.
13
TDDD05 Component-Based Software
SOAP,
An XML-based Interaction Protocol
Body
Header
Envelope
Simple Object Access Protocol
(SOAP)
defines the message format
O. Leifler, IDA, Linköpings universitet.
14
TDDD05 Component-Based Software
SOAP – An XML-Based RPC
 Message contains target address and an envelope
 with
name space, encoding attributes and
 Header
(fixed format), contains
 Authentication
(Sender, Receiver),
 Transactions,
 Error
handling information,
 Routing
 Body
information …
contains user data (free format)
 Transport is transparent, uses predefined channels:
 HTTP
(with back channel, de facto standard)
 SMTP
(Simple Mail Transport Protocol)
 TCP
(with back channel)
O. Leifler, IDA, Linköpings universitet.
15
TDDD05 Component-Based Software
Example: SOAP Header
Message Header
HTTP
POST /TreatmentAdmin HTTP/1.1
HOST: www.hospital-admin.com
Content-Type: text/xml
Charset=“utf-8”
Content-Length: nnnn
SOAPaction: http://localhost/TreatmentAdmin
Each SOAP message
is an XML document
with Envelope as root
element
<SOAP-ENV:Envelope
xmlns:SOAP-ENV=”http://schemas.xmlsoap.org/soap/envelope/">
<SOAP-ENV:Header>
<a:Authentication
xmlns:a=”http://localhost/TreatmentAdmin … “>
…
</a:Authentication>
SOAP Envelope body
</SOAP-ENV:Header>
<SOAP-ENV:Body> … </SOAP-ENV:Body>
</SOAP-ENV:Envelope>
O. Leifler, IDA, Linköpings universitet.
16
TDDD05 Component-Based Software
Example: SOAP Body
<SOAP-ENV:Body>
<m:AddTreatment xmlns:a=http://localhost/TreatmentAdmin>
<treatment>
<patient insurer=“1577500” nr=‘7503100815’/>
<doctor city=“SB” nr=‘4321’/>
<service>
<mkey>1234-A</mkey>
<date>2001-01-30</date>
<diagnosis>No complications.
</diagnosis>
</service>
XML Data
</treatment>
</SOAP-ENV:Body>
O. Leifler, IDA, Linköpings universitet.
17
TDDD05 Component-Based Software
SOAP Interaction Protocol
+ W3C Recommendation (standard)
+ Implements RPC
- Untyped user data, types to encode in the message
- Interpretation of SOAP messages required
- High overhead / low performance
- Ongoing standardizations
Approach
Components of
Web Services
Exists
SOAP
Messaging
Exists
XML
Message Description
Exists
HTTP, FTP, IIOP, MQ...
Network
O. Leifler, IDA, Linköpings universitet.
18
TDDD05 Component-Based Software
TDDD05
Component-Based Software
The Interface Concept
of Web Services
Ola Leifler, IDA, Linköpings
universitet
Service Interface
XML
input / output
Operation
Web Service
Interface
Web Services Description Language (WSDL)
defines a web service's interface
* to describe a service for its clients
* to describe a standard service for WS implementors
O. Leifler, IDA, Linköpings universitet.
20
TDDD05 Component-Based Software
WSDL Interfaces
Interface
 WSDL Ports
 describe
Port
input and output messages
out-port
in-port
 A WSDL Interface is a set of ports
 Functions
with types of parameter and results in XML Schema
 Event ports
 Port types and their operations:
 Event
or message based:
 Notification:
 One-way:
data-out port.
data-in port.
 Call-based
 Request-Response:
 Solicit-Response:
O. Leifler, IDA, Linköpings universitet.
receive, then reply (callee port)
send, then receive (caller port)
21
TDDD05 Component-Based Software
WDSL Specification Structure
 Types
 In
XML schema or another typing language
<wsdl:definitions
 Messages
xmlns:wsdl = “http://w3.org/...”>
<wsdl:documentation ... />
 The data that is communicated
<wsdl:types> Schema imports
</wsdl:types>
 Port types and Operations
<wsdl:message> Messages
 An interface of the service,
</wsdl:message>
grouping sets of messages into operations, <wsdl:portType> Operations
</wsdl:portType>
with input, output, fault parameters
<wsdl:binding> ProtocolsFormats
</wsdl:binding>
 Binding
<wsdl:service> Service definition
</wsdl:service>
 A mapping of the port to underlying
</wsdl:definitions>
messaging layer, e.g., HTTP, SOAP, or MIME
 Service
 A set
of related ports, with service name and location
O. Leifler, IDA, Linköpings universitet.
22
TDDD05 Component-Based Software
WSDL Interface, Message Types
(XSD Types)
<wsdl:types>
<XMLSchema:schema … [target name space definitions]>
<XMLSchema:element name=“addTreatment”>
<XMLSchema:complextype>
<XMLSchema:sequence>
<s:element minOccurs="1"
maxOccurs="1" name="parameter"
nillable="true"
type="a:treatment"/>
</XMLSchema:sequence>
</XMLSchema:complextype>
</XMLSchema:element>
<XMLSchema:element name=“addTreatmentResponse”>
<XMLSchema:complextype>
<XMLSchema:sequence>
<s:element minOccurs="1"
maxOccurs="1" name=“result"
nillable="true"
type="XMLSchema:bool"/>
</XMLSchema:sequence>
</XMLSchema:complextype>
</XMLSchema:element>
<XMLSchema:complextype name=‘treatment’> …
TDDD05 Component-Based Software
</XMLSchema:complextype>
O. Leifler, IDA, Linköpings universitet.
23
Example (cont.):
WSDL Interface Definition
<wsdl:definitions [name space definitions]>
<wsdl:types> … </wsdl:types>
<wsdl:message name=“addTreatmentSOAPIn”>
<part name=“parameters” element=“addTreatment”/>
</wsdl:message>
<wsdl:message name=“addTreatmentSOAPOut”>
<part name=“parameters” element=“addTreatmentResponse”/>
</wsdl:message>
<wsdl:porttype name=“TreatmentAdminSOAP“>
Actual interface
<wsdl:operation name=“addTreatment“>
<wsdl:input message=“addTreatmentSoapIn“/>
<wsdl:output message=“addTreatmentSoapOut“/>
</wsdl:operation>
</wsdl:porttype>
<binding [binding to SOAP / HTTP Protocols] …>
<wsdl:service name=”TreatmentAdminSOAP”>
...
<wsdl:port binding=”...” name=”...”>
<soap:address location=”http://localhost:8080/soap/servlet/rpcrouter”/>
</wsdl:port>
</wsdl:definitions>
O. Leifler, IDA, Linköpings universitet.
24
TDDD05 Component-Based Software
Binding
Binding maps WSDL messages (as defined in portType)
to a messaging layer:
• encoding (e.g. SOAP, RPC) and
• protocol (e.g. HTTP, SMTP, FTP)
<wsdl:binding name=”livetoken” type=”Token”>
<soap:binding style=”document”
SOAP messages
will be bound to
HTTP
transport=”http://schemas.xmlsoap.org/soap/http”/>
<operation name=”GetLastPrice”>
<soap:operation
soapAction=”http://www.stocktrade.com/GetPrice”/>
<input> <soap:body use=”literal”>
</input>
<output> <soap:body use=”literal”> </output>
</operation>
<wsdl:binding>
O. Leifler, IDA, Linköpings universitet.
25
TDDD05 Component-Based Software
WSDL Advantages
 WSDL abstracts from underlying
Protocol
Binding
to HTTP, SOAP, MIME, IIOP, etc.
Component
model
Mappings to CORBA, EJB, DCOM, .NET
are available
 Advantages:
Contrary
to all component models seen so far,
WSDL unifies call and event ports
And
abstracts from the underlying component model,
introducing the component model as a secret
O. Leifler, IDA, Linköpings universitet.
26
TDDD05 Component-Based Software
WSDL Service Interface
+ W3C Standard (WSDL 2.0 May 2007, www.w3.org/TR/2007)
+ Imitates Interface Definition Languages e.g. CORBA IDL
+ Part of BPEL (see later)
- No inheritance on WSDL
- Not recursively composable
Approach
Components of
Web Services
Exists
WSDL
Service Description
Exists
SOAP
Messaging
Exists
XML
Message Description
Exists
HTTP, FTP, IIOP,...
Network
O. Leifler, IDA, Linköpings universitet.
27
TDDD05 Component-Based Software
Web service catalogization
and discovery
UDDI Server
“Where is a
webservice for XY?”
“register my
web service for XY”
Web Service
Provider
O. Leifler, IDA, Linköpings universitet.
Client
28
TDDD05 Component-Based Software
Offer and Find Web Services
 Standardized registry, publishing, advertisement …
 Extended name server, describing interface and properties
 XML Descriptor
 White
Page:
 Yellow Page:
 Green Page:
Address
Semantics (based on standard taxonomy)
Technical specification of service
 Logically central, physically distributed data base
 A web service itself
Universal Description, Discovery and Integration
(UDDI)
O. Leifler, IDA, Linköpings universitet.
29
TDDD05 Component-Based Software
UDDI
White
Page
Registered (and other) names
Service Description
Contact person (name, e-mails, …)
Telephone/fax number
Web site
…
Yellow
Pages
Service category
Type of industry
Type av products/services
Geographic localization
…
Green
Pages
O. Leifler, IDA, Linköpings universitet.
Offered service (WSDL interfaces)
Documentation, description
Principles cooperation realization
…
30
WSDL
WSDL
TDDD05 Component-Based Software
UDDI, WSDL, and SOAP
in a Web Service Interaction
UDDI
Registry
WSDL
Document
2
2
4
Web Service
4. WSDL document
provides metadata to
interact with Web
service
5. Client sends SOAP
message request
5
Client
6
O. Leifler, IDA, Linköpings universitet.
2. Registry refers client to
WSDL document
3. Client accesses WSDL
document
3
1
1. Client queries registry
to locate service
31
6. Web service returns
SOAP message
TDDD05
Component-Based Software
response
UDDI, coming features
 Current OASIS standard is UDDI v3.02 (2005, working group
closed 2010)
www.uddi.org
O. Leifler, IDA, Linköpings universitet.
32
TDDD05 Component-Based Software
Offer and Find Services
- Required and approached.
UDDI v.3 (2003) by OASIS UDDI TC
- made part of the Web Services Interoperability consortium (WS-I)
- Public registries for test existed until 2006.
- Microsoft has abandoned UDDI in favor of BizTalk.
Approach
Components of
Web Services
??
UDDI
Service Discovery
??
UDDI
Service Publication
Exists
WSDL
Service Description
Exists
SOAP
Messaging
Exists
XML
Message Description
Exists
HTTP, FTP, IIOP,...
Network
O. Leifler, IDA, Linköpings universitet.
33
TDDD05 Component-Based Software
TDDD05
Component-Based Software
Business Processes on the Web
with BPEL
BPEL = WS-BPEL = BPEL4WS =
Business Process Execution Language
for Web Services
Ola Leifler, IDA, Linköpings
universitet
Business Process
 How to define a business process on the web?
 There are many languages proposed today:
WSFL, WSCL, WSCI, XLANG, WSEL, UML2, WSUI,
WSXL, BPML, BPMN, …
 IBM & Microsoft: BPEL, BPEL4WS, WS-BPEL
 OASIS: WS BPEL www.oasis-open.org
WS-BPEL 2.0 Jan. 2007
Business
Process
(common task)
O. Leifler, IDA, Linköpings universitet.
35
TDDD05 Component-Based Software
Ingredients...
 BPEL is an architectural language for web services
 Based
on workflow languages
 Orchestration
of business processes
 Invoke
web services
 Mixing
control and data flow operators
 BPEL is a composition language
 Composing
 Relying
new web services from existing ones, using their ports
on messages (events) and calls
 BPEL builds on WSDL
 For
service interface descriptions
 BPEL adds connections (partner link types)
O. Leifler, IDA, Linköpings universitet.
36
TDDD05 Component-Based Software
Side Stepping:
Which Operational Specifications Exist?
 Data flow graphs
 Data
flows through operations
 Activity
diagrams: data flows through actions
 Control-flow graphs
 Nodes
are control-flow operations that start other operations on a state
 Mixed approaches
 Program
dependence graph; Static-single-assignment graphs, SSA
 Cycles
are marked by phi-nodes that contain control-flow guards
 Statecharts:
 Petri
Events trigger state transitions
nets, UML2 activity diagrams: tokens mark control and data-flow
 Workflow
languages: mix control and data-flow, similar to activity diagr.
O. Leifler, IDA, Linköpings universitet.
37
TDDD05 Component-Based Software
Background: UML Activity Diagrams
 Based on Petri Nets
 Dual to State Machines
 In UML 2.0
O. Leifler, IDA, Linköpings universitet.
38
TDDD05 Component-Based Software
Workflow Languages
 A workflow language specifies control and data flow
over a set of operations
 The
operations need not be executed automatically,
but can be performed by humans
 The
workflow allows concurrency,
because it must model the business process of a company
 Workflows
are closely related to Colored Petri Nets
and dual to statecharts
 Examples:
 ARIS
system for SAP [IDS Scheer, Saarbrücken]
 FlowMark
 Lotus
 YAWL
[IBM]
Domino [IBM]
[van der Aalst, Eindhoven]: based on Colored Petri Nets
 UML2 Activity
O. Leifler, IDA, Linköpings universitet.
Diagrams
39
TDDD05 Component-Based Software
Typical Operations
in Workflow Languages
 AND-split: all
Activity
Token
Example:
AND-split
 XOR-split: 1 of n
 OR-split: m of n
 AND-join: all of n
 XOR-join: 1 of n
Example:
 OR-join: m of n
AND-join
O. Leifler, IDA, Linköpings universitet.
40
TDDD05 Component-Based Software
Workflow Engines
 Workflow engines are interpreters of workflows
They
manage the concurrency in a workflow
and synchronize all processes
 Usually, they also support interactive applications
Undo
Transactions
with rollback and commit
Compensation
(in case of error)
 They are, for web services and component systems,
composition engines that execute a composition program
O. Leifler, IDA, Linköpings universitet.
41
TDDD05 Component-Based Software
BPEL Made Simple
 BPEL is an activity-diagram like language,
with
concurrency and transactions
with
different kind of join and split operators
with
ports and connections
BPEL can
be edited graphically,
and has an XML abstract syntax
 Creating a web service becomes a similar activity
to editing an UML activity diagram
O. Leifler, IDA, Linköpings universitet.
42
TDDD05 Component-Based Software
BPEL Specification Structure
 Process definition
 Header
with namespace declarations
 Variables: global variables of the process
 PartnerLink declarations: interface declaration
 with
whom is the process connected?
 Partners: actual partners of the communication
 Correlation sets:
 Which
instance of a process is talking to which other instance?
 Fault handler: What happens in the case of an exception?
 Compensation handler: compensation actions
 Event handler: what happens in case of a certain event?
 A (structured) main operation: e.g., sequence or flow
O. Leifler, IDA, Linköpings universitet.
43
TDDD05 Component-Based Software
WSDL Definitions as a Basis
 BPEL uses WSDL definitions
to define types, message types, and port types
WSDL definitions
Bindings
deployed
–
can be without binding
can be added when the BPEL process is
Statically / at deployment time / dynamically (lookup) /
dynamically (callback)
That
increases reuse of the process
This
achieves component model transparency
(independence of the underlying component model)
 BPEL adds partner link types (connector types)
which
are typed connections
O. Leifler, IDA, Linköpings universitet.
44
TDDD05 Component-Based Software
A Simple Pizza Order in BPEL
<!-- Process definition -->
<process name=”OrderPizza” suppressJoinFailure=”yes”
xmlns=”http://schema.xmlsoap.org/ws/2003/03/business-process”
pns=”http://www.pizza.org/schema”>
<partnerLinks>
<partnerLink name=”PizzaService” partnerLinkType=”pns:OrderChannel”
myRole=”PizzaOrderer”>
Connector
</partnerLinks>
<!-- Global Variables -->
<variables>
<variable name=”input” messageType=”PizzaOrder”/>
<variable name=”output” messageType=”PizzaDelivery”/>
</variables>
<faultHandlers> ... </faultHandlers>
<sequence name=”body”>
<invoke name=”order” partnerLink=”PizzaService” portType=”PizzaOrderPort“
operation=”body” variable=”output”>
<receive name=”acknowledgement” partnerLink=”PizzaService” portType=”PizzaServicePort“
operation=”body” variable=”input”>
</sequence>
O. Leifler, IDA, Linköpings universitet.
45
TDDD05 Component-Based Software
BPEL composes services in abstract services at
the port type level, not at the port/instance level.
To execute, we must bind each partnerLink along
which a partner is invoked to a concrete endpoint.
Partner links
BPEL
BPEL
Process
”OrderPizza”
PartnerLink
”PizzaOrder”
Process
”DeliverPizza”
partnerLinkType ”OrderChannel”
PartnerLink
”PizzaOrder”
Role
Role
”PizzaOrderer” ”PizzaService”
PLType=”OrderChannel”
myRole=”PizzaOrderer”
PLType=”OrderChannel”
myRole=”PizzaService”
receive
invoke
WSDL
WSDL
sequence
portType
portType
”PizzaServicePort”
”PizzaOrderPort”
Operation
Operation
”order”
”acknowledgement”
receive
invoke
Figure partly adapted from S. Weerawarana et al.: Web Services Platform Architecture, 2005.
O. Leifler, IDA, Linköpings universitet.
46
TDDD05 Component-Based Software
Flow Operations are Workflow Graphs
 The <flow> operation is structured as a workflow graph
 The
names of messages, ports, partner links help to span up the graph
 <flow>
executes its sequences in parallel
 <links>
denote dependences between tasks
<flow>
<links><link name=”A”> </link>
<link name=”B”> </link>
A
</links>
<sequence>..<invoke> <source name=”A”>..</sequence>
B
<sequence>....<target name =”B”>...........</sequence>
</flow>
O. Leifler, IDA, Linköpings universitet.
47
TDDD05 Component-Based Software
Other BPEL Operations
 Primitive activities
 Structured control-flow
invoke
... a WSDL-described operation
sequence – serial
composition
receive
– wait for
message
switch
wait
... for some time
while
flow
assign
– copy data from
one data container to
another
– parallel composition
pick (XOR join) – nondet.
choice
terminate
reply
... to external source
throw
 scope – group activities for
... an exception
O. Leifler, IDA, Linköpings universitet.
(can be nested)
common exception handler
48
TDDD05 Component-Based Software
BPEL Tools
 Oracle BPEL Process Manager (formerly Collaxa designer)
 www.oracle.com
 BPMN
 graphical
frontend modeling language for BPEL
 Looks
similar to UML2 Activity Diagram notation
(more symbols for transactions, specific events, …)
 Tools: Orchestra designer
WebSphere Studio, …
(open source, Eclipse plugin), IBM
 www.omg.org/docs/formal/08-01-17.pdf
 People work on the translation of Colored Petri Nets and UML activity
diagrams from and to BPEL
 Colored
Petri Nets have good formal features
and can be used for deadlock checking, etc.
 E.g.,
YAWL [van der Aalst]
O. Leifler, IDA, Linköpings universitet.
49
TDDD05 Component-Based Software
BPMN
Business Process Modeling Notation [OMG 2006] www.bpmn.org
 UML Activity diagram like modeling language for business processes
 Based on Petri Nets
 Nodes 1: Activities, Events, Gateways (branch/fork/join)
 Nodes 2: Data objects (e.g. messages), Start state, End state, …
 Edges: Sequence (control flow), Message flow, Association
 Grouping/Scoping: Swimlanes, Group
 Zoom-in/-out to subprocess view
 Special support for transactions, undo, exception flow, …
 De-facto standard for process modeling
 Good tool support
 Too few ”service interaction patterns” pre-defined  needs extensions
 Not entirely equivalent to BPEL
O. Leifler, IDA, Linköpings universitet.
50
TDDD05 Component-Based Software
Receive Invoice
+
Order
+
Receive Pizza
Send
Invoice
+
+
O. Leifler, IDA, Linköpings universitet.
Send
Pizza
PIZZABAKER
Place
Pizza
Request
Place
Invoice
Request
PAYMENT
ORG.
PIZZA-SERVICE
ORDERPIZZA
BPMN Example
Figure adapted from G. Decker: Choreografiemodellierung – Eine Übersicht, Informatik Spektrum 31(2), April 2008
TDDD05 Component-Based Software
51
Model Verification
 Check for structural incompatibility
e.g., mismatch in message types
 Check for behavioral incompatibility
 Deadlock
Transfer
money
PIZZABAKER
example:
PAYMENT
ORG
e.g., deadlock risk
O. Leifler, IDA, Linköpings universitet.
Send
pizza
52
I do not pay for
the pizza before
it has been sent
to the pizza
orderer
I do not send the
pizza before the
money has
arrived
TDDD05 Component-Based Software
Business Process
Approach
Components of
Web Services
Evolution
BPEL BPMN WSCI
Workflow
??
UDDI
Service Discovery
??
UDDI
Service Publication
Exists
WSDL
Service Description
Exists
SOAP
Messaging
Exists
XML
Message Description
Exists
HTTP, FTP, IIOP,...
Network
O. Leifler, IDA, Linköpings universitet.
53
TDDD05 Component-Based Software
Trust and Security
 Integrity: intact, unchanged
 Confidentiality: encryption policy
 Authentication: proof of identity
 Authorization: access to execute certain services
 Non-Repudiation: warranty on failure
 Legal Rights: copyrights, reselling rights, ...
 Privacy: handling personal data
 ...
O. Leifler, IDA, Linköpings universitet.
54
TDDD05 Component-Based Software
Trust and Security
OASIS standard (2003, 2006) v1.1
Converging
BPEL BPMN
WSCI
Work Flow
UDDI
Service Discovery
??
UDDI
Service Publication
Exists
WSDL
Service Description
Exists
SOAP
Messaging
Exists
XML
Message Description
Exists
HTTP, FTP, IIOP,...
Network
55
Security
??
O. Leifler, IDA, Linköpings universitet.
Exists
WS-Security
Components of
Web Services
TDDD05 Component-Based Software
Technical Conclusion
Defined with XML
Web Services minimum
WS-Security
BPEL BPMN WSCI
UDDI
UDDI
WSDL
SOAP
XML
HTTP, FTP, IIOP,...
O. Leifler, IDA, Linköpings universitet.
56
TDDD05 Component-Based Software
Limitations of
Classical Component Systems
 Different basic communication of the systems,
CORBA components cannot talk directly with COM
components etc.
Adaptation on technical level necessary
 Not full remote transparency
 Dependence on the component model
O. Leifler, IDA, Linköpings universitet.
57
TDDD05 Component-Based Software
Web Services –
Component Model Transparency
 Language adaptation: XML Schema + WSDL
 Location transparency: SOAP (+ HTTP)
 Component model transparency (EJB, COM+, CCM, ...)
Remote
Client
Java
Local
Client
C
Server
C++
EJB
CCM
COM+
WSDL
WSDL
WSDL
SOAP (HTTP) Local
SOAP (HTTP) Remote
O. Leifler, IDA, Linköpings universitet.
58
TDDD05 Component-Based Software
TDDD05
Component-Based Software
Web Services and Java
Ola Leifler, IDA, Linköpings
universitet
Java and Web Services
Java offers APIs and tools
for manipulating XML files and
for generating SOAP messages to interface with web services
 JAXP,
JAXB, JAXRPC, JAXM, JAXR, ...
Technical requirements:
 Java JDK
 Apache Axis (plug-in for Tomcat application server)
 Framework
for constructing SOAP processors for clients and servers
 Generation
of WSDL via a Java API (or automatic creation from class
file)
 Generation
of Java stubs and skeletons from WSDL (or using POJO)
 Tomcat application server
tomcat.apache.org
 Apache HTTP server
httpd.apache.org
O. Leifler, IDA, Linköpings universitet.
61
TDDD05 Component-Based Software
Java and Web Services
Necessary Java APIs:
 JAXP (XML processing),
 JAXB (XML binding),
 JAX-RPC (XML-based RPC),
 JAXM (XML messaging),
 JAXR (XML registries)
O. Leifler, IDA, Linköpings universitet.
62
TDDD05 Component-Based Software
TDDD05
Component-Based Software
Evaluation of Web Services
as composition system
Ola Leifler, IDA, Linköpings
universitet
Component Model
 Mechanisms for secrets and transparency: very good
Location,
language, component model transparency
Communication
protocol transparency
 Generic BPEL Web Services (without bound WSDL ports)
O. Leifler, IDA, Linköpings universitet.
64
TDDD05 Component-Based Software
Composition Technique
 Mechanisms for connection
 Protocol
 WSDL
transparency allows for flexible connections
binding is flexible
 Mechanisms for aspect separation
 Mechanisms for Meta-modeling
 Used
 Scalability: Better
 Changes
of protocol possible
 Changes
of distribution easy
 Changes
of workflow easy
O. Leifler, IDA, Linköpings universitet.
65
TDDD05 Component-Based Software
Composition Language
 BPEL workflows are a nice composition language
Not
yet full exchangeability of connector types
But
graphic support for workflow specifications
 Metacomposition is possible...
The
generation of a BPEL script is easy,
because it is XML based
BPMN
modeling language as frontend to BPEL
Environments
such as Oracle/Collaxa BPEL server
will generate workflow from other specifications
Generic
workflow architectures will be possible
O. Leifler, IDA, Linköpings universitet.
66
TDDD05 Component-Based Software
Web Services
as Composition Systems
Component Model
Composition Technique
Contents: Completely hidden
Adaptation: well supported
Binding points: WSDL ports
Automatic transactions, recovery
Several types of connectors
Composition Language
BPEL is a workflow language for
orchestrating web services
Implicit connectors for architecture
O. Leifler, IDA, Linköpings universitet.
67
TDDD05 Component-Based Software
Wrap-up
The Ladder of Component and Composition Systems
Aspect Systems
View Systems
Aspect Separation
Composition
Operators
Aspect/J
Architecture Systems
Software
Composition
Systems
Composition
Language
Invasive Composition
Static Metaprogramming
Darwin Skeletons
Architecture as Aspect CoSy
Web Services BPEL
SOP
Web services (excl. BPEL) Global Interoperability
.NET CORBA
Beans EJB COM
Classical
Component Systems
Standard Components
Object-Oriented Systems
Objects as
Run-Time Components
C++
Modular Systems
Modules as CompileTime Components
Modula
O. Leifler, IDA, Linköpings universitet.
68
Java
Ada-85
TDDD05 Component-Based Software