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Reference Architecture
and Agile Development
Presentation to NASA Standards Process Group
Reference Architecture workshop at
the ESIP Federation Meeting
George Percivall
OGC Chief Architect
22 July 2010
Copyright © 2010, Open Geospatial Consortium, Inc.
Reference Architecture and Agile Development
• Architecting
• Reference Architectures
• Agile Development
• Some examples
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Copyright © 2010, Open Geospatial Consortium, Inc.
Architecture and Architecting
• Architecture
– Organization of a system embodied in its components, their
relationships to each other and to the environment and principles
guiding its design and evolution (IEEE P1471)
• Architecting Approaches
– Heuristics: Rule of thumb
– Stakeholders:
Process
– Normative: Standards
Systems Architecting, Eberhardt Rechtin, Prentice Hall, 1991
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Copyright © 2010, Open Geospatial Consortium, Inc.
Architecting Heuristics
• The greatest leverage in system architecting is at the
interfaces - Eberhard Rechtin
• Look for misfits with context and design to minimize them Christopher Alexander
• Running code wins - IETF
• Solutions should be as simple as possible, but no simpler –
Albert Einstein
• Simple ain’t easy – Thelonious Monk
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© 2006, Open Geospatial Consortium, Inc.
4
Reference Architecture Standards
• IEEE 1471
– General process. Requires viewpoints but does not define any.
• RM-ODP
– Reference Model for Open Distributed Processing
– Enterprise, Informational, Computational, Engineering, Technology
– Viewpoint languages coordination with UML
• OASIS Reference Model for Service Oriented Architecture
– Focused on Services
• Others: DODAF, TOGAF, Zachman
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Copyright © 2010, Open Geospatial Consortium, Inc.
SUMMARY OF ARCHITECTURE STANDARDS
Source: GST Interoperability Group, 2002
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SUMMARY OF ARCHITECTURE STANDARDS
• Maintenance organization – what organization is responsible for establishing,
updating and distributing the standard.
• Architecting products defined? – Does the standard define what items, e.g.,
views, shall be used to define an architecture?
• Architecting process defined? – Does the standard define the steps that an
organization shall perform in order to develop an architecture?
• Standards Category Model? – Does the standard provide an outline for
organizing standards that shall be used to define architectures. (These
categories are the basis for a Standards Technical Reference Model)
• Required standards listed? – Does the standard provide specific standards that
shall be used to be compliant to the architecture standard?
• Standards Development Process? – Does the standard define a process for
developing or adopting standards?
• The Zachman Framework is not included in the evaluation as it is a proprietary
approach not allowing for comparison.
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Copyright © 2010, Open Geospatial Consortium, Inc.
RM-ODP Viewpoints – Separation of Concerns
“GIGAS Methodology for comparative analysis of information and
data management systems” OGC Best Practice, 10-028r1
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Examples of Reference Architecture for
Evolutionary Development
• OGC Reference Model (ORM)
– Overview of OGC Standards Baseline
– Resource for defining architectures for specific applications
• GEOSS Architecture Implementation Pilot
– System of Systems based on Interoperability Arrangements
– Process of iterative development while refining an architecture
– AIP Architecture using RM-ODP
• http://www.ogcnetwork.net/AIpilot
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Copyright © 2010, Open Geospatial Consortium, Inc.
GEOSS AIP Enterprise Viewpoint
GEOSS AIP Information Viewpoint
Source: GEOSS AIP-3 Architecture – Information Viewpoint
Engineering Viewpoint
GEOSS Common
Infrastructure
Main GEO
Web Site
Registered Community
Resources
Client Tier
GEO
Web Portals
Registries
Components
& Services
CSW
Standards and
Interoperability
Best Practices
Wiki
Community
Portals
WMS
CSW
CSW
Client
Applications
WMS
CSW
Business Process Tier
CSW
Community
Catalogues
GEOSS
Clearinghouses
W*S
Mediation
Servers
Alert
Servers
WPS
User
Requirements
Workflow
Management
WMS
GEONETCast
WFS
WFS
Product Access
Servers
SOS
Processing
Servers
SAS
SPS
Sensor Web
Servers
W*S
Test
Facility
Access Tier
Model Access
Servers
ISO 19101-2 – Geographic Information – Reference Model – Imagery
Engineering viewpoint - Nodes
OGC
13
Prototyping Versus Specifying
• “Prototyping Versus Specifying: A Multiproject Experiment”
1) Prototyping yielded products with roughly equivalent performance,
but with about 40 percent less code and 45 percent less effort.
2) The prototyped products rated some what lower on functionality and
robustness, but higher on ease of use and ease of learning.
3) Specifying produce produced more coherent designs and software
that was easier to integrate.
– BARRY W. BOEHM, TERENCE E. GRAY, AND THOMAS
SEEWALDT, IEEE TRANSACTIONS ON SOFTWARE
ENGINEERING, VOL. SE-10,NO. 3,MAY 1984
• See also Michael Schrage, e.g., Serious Play and “Cultures
of Prototyping” in Bringing Design to Software
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Copyright © 2010, Open Geospatial Consortium, Inc.
Agility and Architecture
• Use agile development to get to a good architecture by
appropriately applying suitable combinations of
– architectural functions
• (such as communication, quality attributes, and design
patterns) and
– architectural skills at four points in the development life
cycle.
• (up-front planning, storyboarding, sprint, and working
software)
• http://www.computer.org/cms/Computer.org/ComputingNo
w/homepage/2010/0410/T_SW_AgileArchitectureInteractio
ns.pdf
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Copyright © 2010, Open Geospatial Consortium, Inc.
IEEE SOFTWARE - March/April 2010
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GEO AIP Evolutionary Development Process
Participation
AR-07-02 Architecture Implementation Pilot
Evolutionary Development Process
Concept
Development
Participation
Call for
Participation
Updates for each step
Continuous interaction
with external activities
Participation
Kick-off
Workshop
Architecture
Documentation
Baseline
Operational Baseline and Lessons Learned for next evolutionary spiral
Participation
Development
Activities
Participation
Persistent
Operations
(AR-07-01)
AIP: Using the Architecture Views in the
Evolutionary Development Process
1.
SBA
Scenarios
2.
Enterprise
Models
Optimize
3.
Engineering
Design
Specify
Information Framework
Use Cases
Component Types
Services
4.
Deployment
Plan
David Byrne:
How Architecture helped music evolve
• http://www.ted.com/talks/david_byrne_how_architecture_helped_music_evolve.html
• He asks: Does the venue make the music?
– From outdoor drumming to Wagnerian operas to arena rock, Byrne
explores how context has pushed musical innovation.
• Model for creation (at 13:45 in talk)
– We make music primarily in a form to fit the context and we make art
to fit museum walls
– We write software to fit existing operating systems. Its evolutionary,
its adaptive.
– This is a reverse view from the traditional romantic view: first comes
the outpouring of emotion and then somehow it gets shaped into
something.
– The passion is still there, but the vessel that it is going to be injected
into and poured in to is instinctively and intuitively created first.
Making Location Count…
Copyright © 2010, Open Geospatial Consortium, Inc.
For Details on OGC Standards…
• OGC Standards
– Freely available
– www.opengeospatial.org/standards
• OGC Reference Model (ORM)
– Overview of OGC Standards Baseline
– Resource for defining architectures for specific
applications
– www.opengeospatial.org/standards/orm
George Percivall, gpercivall at opengeospatial.org
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Copyright © 2010, Open Geospatial Consortium, Inc.