UniFrame: An Exercise in Developing Distributed Software Systems

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• UniFrame An Exercise in Developing Distributed
  Software Systems
• Rajeev R. Raje
• IUPUI

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Why Distributed Computing Systems (DCS)?

• Need to build reliable systems which can take
  advantage of geographically dispersed computer
  and data resources
• Demanding applications -- to run on a single host
• Limitations of pure client-server model are
  reached -- need for newer and effective paradigms

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Enablers for Proliferation of DCS

• Advances in hardware and networking technologies
• The world is getting inter-connected
• An inherent distributedness and complexity in
  applications

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Applications

• Telecommunication
• Multi-media Information Access
• Health-care
• Financial -- Trading, Insurance
• Human-Computer Collaborations
• Distributed AI
• High-performance Meta-computing

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What is a DCS?

• A DCS consists of multiple autonomous processors
  that do not share primary memory but cooperate by
  sending messages over a communication network
• A DCS consists of a collection of autonomous
  computers linked by a network and equipped with
  distributed system software

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Software is Complex!

• It Challenge of Programming has already taught
  us a few lessons, and the one I have chosen to
  stress in this talk is the following. We shall do
  much better programming job, provided that we
  approach the task with a full appreciation of its
  tremendous difficulty, provided that we stick to
  modest and elegant programming languages,
  provided that we respect the intrinsic limitation
  of the human mind and approach the task as very
  humble programmers.
• -- E. W. Dijkstra
• (1972 ACM Turing Award Lecture)

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Key Challenges in Developing Software for DCS

• Openness
• Heterogeneity
• Concurrency
• Scalability
• Fault Tolerance
• Transparency
• Developing High-confidence Software for DCS is a
  Complex Task!

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UniFrame Overview
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Vision of UniFrame
Automate the process of integrating
heterogeneous components to create distributed
systems that conform to quality requirements
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Current Objective

• Create a Framework that will enable a seamless
  interoperation of heterogeneous distributed
  components
• Directions
• Process for Distributed System Generation
• Representation and Interoperation of Components
• Techniques for Reasoning about Quality
• Validation through Experimentation

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Key Research Issues

• Architecture-based Interoperability (UAB IUPUI)
• Automation, standardization, mappings and tools
• Distributed Resource Discovery (IUPUI)
• Specification, publication, distribution,
  selection
• Validation of Quality Requirements (NPS IUPUI)
• Vocabulary and associated metrics, composition,
  monitoring

Main Challenge Heterogeneity
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Assumptions

• Distributed system construction by integrating
  independently deployed heterogeneous components
• Accepted knowledgebase with explicit quality
  requirements
• Presence of distributed component repositories
• Known certification mechanisms for quality
  attributes
• Advantages of automation
• Increased reliability
• Shorter delivery time

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UniFrame Solution
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UniFrame Process An Overview
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UniFrame Process

• Knowledgebase
• Distributed System Constructor

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UniFrame Knowledgebase

• Created by experts
• Hierarchical business line architecture
• Standards-based
• Categorized by features
• Mapping to design models (component-based)
• Service-oriented hierarchy
• Realizes MDA mapping of Platform Independent
  Models to Platform Specific Models
• Facilitates interoperability

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Overview of System Constructor

• Given requirements for a DCS,
• finds a design specification in the
  knowledgebase,
• collects the specified component implementations,
• integrates them into the designed DCS,
• tests against the requirements (white black
  box).
• Supports iterative, incremental development

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Salient Features

• Increases product quality through
• use of well-tested designs and components
• automation in construction and testing
• Decreases development time through
• use of predefined domain and design models
• automation

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UniFrame Resource Discovery Mechanism
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UniFrame Resource Discovery Mechanism

• Unified Meta-component Model (UMM)
• Component
• Specification
• Service
• Quality attributes, selection
• Infrastructure
• Registration, publication, discovery

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Components

• Heterogeneous and distributed
• Adhere to the standardized knowledgebase
• Code UMM specification
• Quality assurance through the design by
  multi-level contract
• Beugnard, et al IEEE/Computer 1999
• UMM specification includes
• Inherent attributes, functional attributes,
  non-functional attributes, cooperative
  attributes, auxiliary attributes, deployment
  attributes, creation attributes

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Example of UMM Specification

• Component Name Validation Server
• Domain Name Document Management
• System Name Document Manager
• Informal Description Provides validation
  service.
• Computational Attributes
• a) Inherent Attributes
• ID, Version, Author, Date, Validity,
• Atomicity, Registration, Model
• b) Functional Attributes
• Purpose, Algorithm, Complexity, Syntactic
  Contract, Behavioral Contract, Synchronization
  Contract, Technology, Expected Resources,
  Design Patterns, Known Usages, Aliases

• Cooperation Attributes
• Pre-processing and Post-processing Collaborators
  
• Auxiliary Attributes
• Mobility, Security, Fault-tolerance
• Quality of Service Attributes
• Qos Metrics, QoS Level, Cost, Effect of
  Environment, Effect of usage patterns
• Deployment Attributes N/A
• Creational Attributes Atomic

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Service

• Well-defined concept of the application logic
• Basic composable abstraction
• Need for assured levels of service
• Functional and QoS
• Emphasis on QoS and its validation
• Platform independent QoS catalog
• Description, Measurement, Classification,
  Behavior, and Composition of QoS Parameters
• Assist component developer and system integrator

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Infrastructure

• UniFrame Resource Discovery Service (URDS)
• Hierarchical, Proactive, Interoperable,
  Decentralized
• URDS Constituents
• Active Registries
• Headhunters and Meta-repositories
• Internet Component Broker
• Domain Security Manager, Query Manager, Adapter
  Manager and Link Manager

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UniFrame Resource Discovery Service
Internet Component Broker
Domain Security Manager
Link Manager
Query Manager
Adapter Manager
Query
Authentication
Headhunters
Adapter Components
Meta-Repositories
Proactive Discovery
.NET
RMI
CORBA
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Salient Features

• Meta-model based technique
• Quality assurance through multi-level
  specification and QoS validation
• Platform independent QoS catalog
• Distributed, proactive, hierarchical and
  interoperable discovery service

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Architecture-based Interoperability Glue
Wrapper Construction
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Glue Wrapper Construction

• UniFrame Knowledgebase
• Glue and Wrapper Constructor

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Construction Process

• Knowledgebase
• Business and Technology domain model requirements
• Component type hierarchy
• Associated Rules expressed in Two-Level Grammar
• Constructor
• Inputs
• Discovered components
• Knowledgebase
• Outputs
• Glue and Wrapper code

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Two-Level Grammar (TLG)

• Invented by van Wijngaarden for specifying syntax
  and operational semantics
• Consists of two CFGs type and function
  definitions
• Extended for object orientation

• Used here to indicate rules of code generation
  for component integrations
• Integrated with VDM (Vienna Development Method)
  tools for UML modeling, Java and C code
  generation

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Glue Wrapper Construction
Bridge driver

RMI Document Terminal (DT)
CORBA Validation Server (VS)



Proxy server



Proxy client









TLG specification for
TLG specification for CORBA VS

RMI DT









Business Domain Model


Technology Domain Model

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Salient Features

• TLG class hierarchy provides a means for
  expressing multiple levels of component
  abstractions
• TLG rules provide for validation of feature and
  component compositions
• TLG rules provide code generation necessary for
  bridging component models and QoS instrumentation

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UniFrame Quality Framework Event Grammar
Approach
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UniFrame QoS Framework

• Development of a QoS catalog
• Creation and application of unifying system
  monitoring techniques
• To develop unifying principles for program
  monitoring activities.
• To apply these principles for the validation of
  dynamic QoS parameters.
• To develop and experiment with different
  techniques for implementing these principles.

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Program Behavior Models

• Program monitoring activities can be specified in
  a uniform way using program behavior models based
  on the event notion.
• An event corresponds to any detectable action,
  e.g., subroutine call, message passing, etc. An
  event corresponds to a time interval.
• Two partial order binary relations are defined
  for events precedence and inclusion.
• An event has attributes, such as, type, duration,
  program state at beginning or end of the event
  and value.

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Program Behavior Models

• Event grammar specifies the constraints on
  configurations of events generated at run time
  (axioms, or lightweight semantics of the target
  language).
• Some axioms are generic, e.g., transitivity.
• A PRECEDES B and B PRECEDES C ? A PRECEDES C
• A IN B and B IN C ? A IN C

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Example of Event Grammar

• ex_prog ex_stmt
• ex_stmt ex_assignmt ex_read_stmt
• ex_assignmt eval_expr destination

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Salient Features

• Unifying framework for program monitoring based
  on precise behavior models and event trace
  computations
• Computations on the event traces can be
  implemented in a nondestructive way via automatic
  instrumentation of the source code or even of the
  executables (Dyninst approach).
• Can specify generic trace computations, such as,
  bug detection, dynamic QoS metrics, profiles and
  visualization.
• Both functional and non-functional requirements
  can
• be monitored.
• An alternative approach to aspect-oriented
  paradigm
• Validity of the approach has been shown by
  creating prototypes for different languages, such
  as, Pascal, C and Unicon.

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Summary
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Summary and Salient Features

• Results achieved so far have created a foundation
  for realizing the vision of UniFrame
• Automate the process of integrating
  heterogeneous components to create distributed
  systems that conform to quality requirements
• Unified Approach
• Process, Model Driven technique for automation
• UniFrame Resource Discovery Mechanism
• Multi-level specification, Proactive,
  Interoperable
• Quality of Service Framework
• Vocabulary and associated metrics, Unifying
  system monitoring technique

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Thank YouQuestions?http//www.cs.iupui.edu/uni
Frame