Transaction Integrity in Componentbased Systems

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Transaction Integrity in Component-based Systems

• Kees M. van Hee
• Dept. of Mathematics and Computer Science

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Agenda

• Information systems versus embedded systems
• Component-based world
• Software architecture
• Transaction integrity

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Info systems vs embedded systems

• What do information systems do?
• monitoring of (business) processes
• planning of (business) processes
• execution of (business) processes
• How?
• registration of states of objects and events
• generation of management information
• generating or evaluating decisions
• facilitating the cooperation between people
• processing of transactions

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Info systems vs embedded systems

• information systems support business processes
  inside an organisation, or
• between two or more organizations (so called
  inter-organizational i.s.)
• embedded systems (e.s.) support physical devices
  
• e.s. have more simple data structures
• e.s. have stronger time and resource constraints
• despite the differences, most methods apply to
  both types of systems

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Component-based world (1)

• System network of components
• both hardware and software
• components may reside anywhere
• components are specified and recognized by their
  function and their interface interface
  protocol data types

user interface
component
monitor interface
configuration interface
software interface
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Component-based world (2)

• e.g. a Telco operator is built of ca 20 COTS
  components

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Component-based world (3)

• Different types of components
• application components contain business logic
• generic components support application components
  and have no business logic

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Component-based world (4)

• Parameters of predefined components
• parameters are options, selected from a list or
  input as simple data (often a tree of option
  lists)
• limited flexibility, but easy to use
• little ICT knowledge but much application
  knowledge required

• Parameters of programmable components
• parameters are models, like data models and
  process models
• the model defines the function of the component
• special languages to make models (often diagrams)
• very flexible, but advanced ICT knowledge
  required

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Component-based world (5)

• Component based development is different
• requirements are determined
• an architecture is designed
• components are specified
• components are selected form vendors or
  constructed from scratch
• configuring components parameter setting
• integration is connecting components interfaces,
  often via middleware
• Programming configuring integration
• the architecture is essential

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Component-based world (6)

• component-based systems will behave in an
  organic way
• periodically components will be replaced by
  better ones
• new functionality will be realised by new
  components
• vendors will compete with the best functionality
  of their individual components
• prepacked solutions will be offered by third
  parties
• combinations of components with parameters that
  can be used as a new predefined component
• prepacked solutions can be made by third
  parties
• prepackers will compete with vendors of
  packages
• components may be outsourced to an ASP

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Features of IS to be componentized
Component-based world (7)

• Data management
• User interaction
• Business process
• Business logic
• Component coordination
• Security control

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Generic components and some vendors
Component-based world (8)

• Oracle, Sybase
• OpenIMS, Worldox
• Business objects, Cognos
• Tridion, Tekfuse CMS
• Apache, IIS
• WebLogic (BeaSys), Borland Enterprise Server
• FairIsaac, ILOG
• Staffware, Cosa
• BizTalk, Tibco

• Database man. system
• Document man. system
• Datawarehouse / Dataminer
• Content man. system
• Webserver
• Application server
• Rule engine
• Workflow man. system
• Coordination engine

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Component-based world (9)
Web Server
ApplicationServer
Rule Engine
Workflow Engine
Coordination Engine
Application
Application
Database Manager
Data Warehouse
ContentManager
Document Manager
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Software architecture (1)

• System development requires orchestration
• the architecture is the musical composition.
• Architecture is used
• to divide and conquer
• to define and select components
• to test and integrate components
• to manage a system when it is operational

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Software architecture (2)

• Definitions
• Architecture of a system a consistent set of
  views and rules of the system
• A view is a model of a system (often a graph)
• Views are related to each other
• Rule is a constraint on a view or on a
  combination of views
• Architecture language a language to define views
• Architecture pattern standard solution for
  generic problem

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Software architecture (3)
Example

• business architecture
• process model
• information model
• software architecture
• logical model.....
• physical model................
• infrastructure

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Software architecture (4)

• Component-based architecture
• Components have 4 layers
• Ports to communicate
• Processes with tasks (actions, events)
• Objects to store data, accessible by methods
• Subcomponents
• Processes determine the behavior
• Tasks exchange messages through ports with other
  components
• Tasks execute operations on objects by method
  calls
• (Yaffa Yet another framework for architecture)

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Software architecture (5)

• Processes are the heart of a component
• Can be modeled in different ways e.g.
• Transition system
• Process algebra
• Petri net
• Uml Activity Diagram
• BPMN
• BPEL
• Components execute transactions, tiggered
  externally

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Transaction integrity (1)

• Transactions may start up sub transactions in
  other components
• Transactions should have a clearly defined start
  and end event
• Two correctness criteria
• Proper completion transactions should always be
  able to terminate with an end event, and they
  should not leave any unfinished work
• Invariants constraints on the objects of a
  component should hold as soon as a component has
  finished its transactions

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Transaction integrity (2)

• If we use Petri nets as modeling vehicle
• Processes that are model transactions have the
  structure of workflow nets
• Proper completion is called soundness
• Soundness is decidable and there are software
  tools to check it

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Transaction integrity (3)

• Example with Yasper
• A two component system
• Webservice for query processing
• Processing is outsourced to a second component
• Clients pay in advance
• If the second component has not answered all
  questions before the client stops the payment is
  refunded
• Are transactions handeled correctly?

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Challenges for software architects
Challenges

• The correct orchestration of components
• To isolate functionality in a generic component
• Clear, generic functionality required
• Business plan needed market analysis, who is the
  vendor, do the benefits cover the costs?
• To deal with overlapping functionality
• Which one to use?
• If both have to be used, how do we synchronize
  them?
• Reshuffling of functionality