Flow Composition for the Web Francisco Curbera, Matt Duftler, Rania Khalaf, Douglas Lovell Presentation of the paper: Bite: Workflow composition for the web. F Curbera, M Duftler, R Khalaf, D Lovell, Service oriented computing: fifth international conference, Springer, 2007.
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Bite: Workflow Composition for the Web. Presented at the ICSOC Conference 2007
Presentation with the paper: Bite: Workflow composition for the web. F Curbera, M Duftler, R Khalaf, D Lovell, Service oriented computing: fifth international conference, Springer, 2007.
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Flow Composition for the Web
Francisco Curbera, Matt Duftler, Rania Khalaf, Douglas Lovell
Presentation of the paper: Bite: Workflow composition for the web. F Curbera, M Duftler, R Khalaf, D Lovell, Service oriented computing: fifth international conference, Springer, 2007.
Outline
• Services and resources
• Composition
• Web flows and flow scenarios
• What is next
About SOA and the Web
Services and Resources
• SOA is about composition: process or structural (so far)• SOA assumes:
– A two level development and execution environment (atomic services, composite services)
– Two standard assembly models, BPEL, SCA
• The Web was NOT built on a composition requirement– Assumes HTTP exists, gives clients access to resources– And a few shared data types
• REST resources are not compositional– Resources are information oriented: Data composition?– But many resources have “behavior” - drive processes
• Process composition for the Web?
End-to-end deployment view in SCA
Component/Composite
Component
B
Component
A
Composite
Composite
Entry
Point
implementation
implementation
WireWireWire
Composite
External
Service
End-to-end business logic in WS-BPEL
Partner link
WSDL porttype
Process
The value of the end-to-end view
• Beyond component oriented use/reuse, first class SOA compositions provide an end-to-end view of composite applications
• Supports end-to-end configuration, validation, management, etc.
– Policy driven configuration• Reduce errors in QoS configuration of distributed components,
ensure correctness of complete configuration
– End-to-end static analysis, at many levels• Tools check “compatibility” of a set of composed components:
functional and non-functional
– Runtime monitoring and validation• Uses structural/process topology to interpret monitoring information
Some interesting trends
• Web mashups– Quickly assemble a new end-user applications by
reusing existing ones
• Process centric programming
– Adding the flow perspective to Web apps: Spring Web Flows, continuations
• The Web (REST) interaction model making inroads as an alternative to enterprise models– The SOAP vs POX debate, and other uninteresting
debates
Mashups
• Mash-up is essentially a form of Web application composition– Google maps are consumed and
aggregated with additional information
– Display final result on browser– Aggregate in the client or the
server sides– There are security issues but the
idea is simple
• Data centric• Composition w/o a component
model!
SOA capabilities for the Web?
• How lightweight can we make it? Who is going to use it?
• Common data model?– But we already have one – XML + mime types– XML is already pervasive from the DB to the UI, but it is just one of the relevant data
types
• Component model?– Reuse is nice, when it works. – Do we need machine readable component definitions? Or just good documentation?– Agree on component interaction primitives based on the resource model (ATOM)
• Resource composition– Process oriented – seems unavoidable since processes already run on the Web– Data composition – it is data model dependent, so far– Structural composition (???) – need good use cases probably because so far Web
apps usually don’t expand many Web components
Bite – Process Composition for the Web
Feed Aggregation
receive
fetchYahooFeed fetchBBCFeed
aggregate
sort
reply
Resource aggregationRelies on a well defined data model –ATOM/RSS
Feed Aggregation
receive
fetchYahooFeed fetchBBCFeed
aggregate
sort
reply
HTTP GET
HTTP GET
HTTP GET
Call local code (no overhead):<action name=“aggregate” target=“java:com.ibm.Aggregator”
– Script-like approach to data typing (versus strongly typed interfaces)• Usage implies definition• Errors happen, focus is on short development cycle, typing is optional
– Standard HTTP interfaces (application defined interfaces)• External interactions are resource centric + eMail ☺
– Single protocol – HTTP (extensible protocol set)• All you need – ok, maybe email also.
– HTTP defines all your interactions QoS (extensible, declarative policies)• That gets you a long way
– One tool required: a text editor (many complex tools required to manage all required artifacts)• Fancier tools are available for the typing challenged
What is available now
1. Language specification� Extensive documentation – User Guide, Programming
Guide
2. Full runtime implementation� Currently on ProjectZero.org: tightly architected
according to Zero principles� Positions flow model as an extension of the basic Zero
programming model
3. Tools:� Deployment and management interface� Browser based Delivered with Zero Launch
http://www.ProjectZero.org/
What is next
• Bite profiles through extensibility– Define new activity sets to capture typical steps in
focused use cases:
• Feed manipulation
• Complex user interaction – full browser support
• Core flow QoS: persistence, recovery
– What is the right way to expose these capabilities
• Composite applications beyond flows
Summary
Conclusions
• There is significant value in the PM in the large approach
– Which need not be limited to the enterprise application space
• Web application development is slowly enabling a “service” approach to development
– Reusing large granularity services
– How far will it go?
• A challenge and an opportunity for the SOC community
Thanks!
Questions?
Thanks!
Backup slides
Composition takes place all over – in different models
Browser
Business
Logic Container
Database
Web Container
HTTP/REST Connectors
Local or remote Calls (IIOP,
SOAP?)
Java/.Net c
omposition
Portal composition
Relational data
composition
SOA Composition taking over the middle tiers
Browser
Business
Logic Container
Database
Web Container
HTTP/REST Connectors
Local or remote Calls (IIOP,
SOAP?)
Java/.Net c
omposition
Portal composition
Relational data
composition
Composition coming to the browser
Browser(Javascript/XML)
Business
Logic Container
Database
Web Container
HTTP/REST Connectors
Local or remote Calls (IIOP/SOAP?)
Java/PHP/SOA
composition
Portal composition
Relational data
compositionBrowser mash-ups
Process-centric programming is already here
• Method and page oriented programming has dominated the Web– And most enterprise programming models
• Result is that end-to-end character of a process is lost– Factored out into a set of separate PHP pages, servlets, session beans. Or have to
go through an MVC framework– Business and compositional logic get fragmented– It becomes hard to capture the end-to-end logic of an application, hard to track and
manage
• The focus of successful frameworks and languages has been in easing the DB to HTML access– PHP, Ruby on Rails– Integration is improved across tiers but business logic integration is neglected
• Process centricity is well accepted in the enterprise in the form of WfMSs, modeling tools etc.– But is has barely made an impact on Web programming
Successful Web Frameworks focus on data and presentation
Browser
Database
PHP, Rails
HTTP/REST
Language specific Connectors
Composition is
page aggregatio
Relational data
composition
Continuations in Cocoon -JavaScript
function sellItem() {(...)
var url = "page/getRateAmt";cocoon.sendPageAndWait(url);rate =