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Component Reuse: Benefits and Drawbacks in Software Design

This lecture explores the tradeoffs involved in component reuse in software design, discussing the benefits and drawbacks. It also covers architectural mismatch and the process of identifying and selecting reusable components.

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Component Reuse: Benefits and Drawbacks in Software Design

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  1. Informatics 122Software Design II Lecture 9 André van der Hoek & Alex Baker Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited. February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 1

  2. Today’s Lecture • Component reuse • Assignment 5 February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 2

  3. build(and thus design) buy or get for free(and thus fit into a design) A Critical Design Tradeoff February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 3

  4. build(and thus design) buy or get for free(and thus fit into a design) A Critical Design Tradeoff: Benefits full control full understandingflexibilitycompetitive advantage can be instantaneousexternal support quality February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 4

  5. build(and thus design) buy or get for free(and thus fit into a design) A Critical Design Tradeoff: Drawbacks timecost maintenancestandards licensinglack of customizabilityobsolescenceurgent bugs evaluation cost February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 5

  6. build(and thus design) buy or get for free(and thus fit into a design) A Critical Design Tradeoff can be instantaneousexternal support quality full control full understandingflexibilitycompetitive advantage timecost maintenancestandards licensinglack of customizabilityobsolescenceurgent bugsevaluation cost February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 6

  7. build(and thus design) buy or get for free(and thus fit into a design) Our Focus Today can be instantaneousexternal support quality full control full understandingflexibilitycompetitive advantage timecost maintenancestandards licensinglack of customizabilityobsolescenceurgent bugsevaluation cost February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 7

  8. A New Kind of Design Decision • Less fine control • More learning and using and applying • Similar to recovery February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 8

  9. Architectural Mismatch • Architectural mismatch stems from mismatched assumptions a reusable component makes about the system structure of which it is to be part • Components • functionality • interfaces • behavior • control model • Connectors • protocols • data model • System topology • Construction • dependencies • initialization Difficult to predict a-priori February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 9

  10. Architectural Mismatch • Architectural mismatch stems from mismatched assumptions a reusable component makes about the system structure of which it is to be part • Components • functionality • interfaces • behavior • control model • Connectors • protocols • data model • System topology • Construction • dependencies • initialization How much adaptation is too much adaptation? February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 10

  11. identifypreliminaryarchitecture identifypotentialplaces forreuse establishselectioncriteria (perplace) Component Reuse Process updatearchitecture selectcomponent evaluatecomponents search forapplicablecomponents February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 11

  12. Identify Preliminary Architecture • Largely as usual • Familiarity with certain reusable components may influence the architectural choices being made February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 12

  13. Identify Potential Places for Reuse • There are components for just about anything • graph layout • database access • regular expression handling • numerical computing • protein visualization • speech recognition • e-mail handling • index and search • maps • geocoding • … • Judiciously mark the architecture in terms of where reusable components may fit in February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 13

  14. Establish Selection Criteria (Per Place) • What kind of component does the architecture really need? • functionality • absolutely necessary versus desired functionality • software qualities • How is the component to fit with the rest of the architecture? • some adaptation can be accommodated • Investment • cost • future cost • Reputation • component provider • component itself • … February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 14

  15. Search for Applicable Components • Google is a wonderful thing • www.google.com • code.google.com • Component repositories • rich in available components • many junk • some decent • occasional gems • Research and professional development literature • Too many is no good • Too few is no good either • although one perfect component would solve the problem February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 15

  16. sourceforge.net February 21, 2010 – 18:05:18 (c) 2010 University of California, Irvine – André van der Hoek 16

  17. apache.org February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 17

  18. Evaluate Components • Apply selection criteria to each of the components found • beware of the platform, deployment needs, licensing terms • matrix of criteria versus components • Additional approaches • trial / evaluation licenses • reading component code • examine sample programs using the component • writing code using the component • Examine the component’s documentation • Analyze architectural impact of the component • Perhaps even “mini integrate” the component February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 18

  19. Select Component • Choose the optimum component • understand tradeoffs • be prepared to not choose a component February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 19

  20. Update Architecture • Design any adapters necessary to fit the component • Redesign other components as needed • Restructure architecture as needed • Consider implementers • special role for documentation February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 20

  21. A Quick Sample Among the Graduate Students • Xalan • Xerces • Lucene • Jung • Kaffe • Bcel • Equip • JLoox • Schematron • GraphViz • Jython • Scriptalicious • … • Xacml • SWT • JOAL • Jetty • Batik • JmDNS • Darwin Streaming Server • Spook • Mplayer • MySQL • live.com RTP/RTSP • gaim im client • … February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 21

  22. Assignment 5 • Research available components that provide a particular kind of functionality for Calico, set up selection criteria, make a choice of the component that you believe is best, and detail how you would go about integrating the component • Specifically, research components for the following situations • speech recognition – we want to add the ability to use speech to create text labels, for which we need some sort of speech-to-text conversion component that is as reliable as possible • mouse gestures – we would like to integrate more complex mouse gestures; find an existing component that can recognize mouse gestures reliably, possibly employing a learning algorithm • graphics – we want to replace Piccolo, as it is no longer supported, ideally with a drawing framework that has powerful functionality for future extensions yet has minimal impact on the current architecture • distribution – we would like to replace the current home-grown mechanism with an actual real protocol and middleware that is lightweight, fast, and can handle long distance February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 22

  23. Assignment 5 • Additional constraint • we have $25,000 in funds to spend on this project, but we want to save money for user studies and other assorted expenses, so cost should be (somewhat) minimized • if truly warranted, management can be requested to fund one “big ticket” component, up to possibly $75,000 February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 23

  24. Assignment 5 • Create a 10 minute presentation that describes for one of the four categories (specific assignments of which category by which team on slide 26) • your search process • candidate components you considered • strengths • weaknesses • your selection criteria • the component you deem best (and why) • Create a document that describes, at the design and code level, the impact of incorporating the chosen components (all four) • from this document, someone should be able to make these changes “effortlessly” February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 24

  25. Assignment 5 • Presentation in class Thursday, February 25th • Document due at the beginning of class Thursday, February 25th • Graded on breadth and depth of component evaluation, as well as the thoroughness and insightfulness of the document • Each person also needs to submit a team evaluation (new forms available on class webpage) February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 25

  26. Team Assignments • Team 1 (speech) • ZIMING DAI • RYAN CHRISTOPHER HSU • SEAN LEW TSUSAKI • KYLE STEPHEN LUTZE • JAMES RICHARD BENSON Team 2 (mouse) • TAE SUNG KIM • JORDANIEL CHARLES WOLK • ARREN APPLEBAUM • SOHRAB HEJAZI • GARRETT KIM Team 3 (graphics) • RYAN SCOTT NISSENBAUM • STACEY THUY VI DAO • HUNTER GLENN GILLANE • ALEX RYAN CHUNG • MATTHEW JAMES PALMER • Team 4 (distibution) • SAMUEL JAMES KAUFMAN • KYLE PHILLIP MUSLER • PATRICK CHAO-CHENG LU • JOSHUA ALEXANDER PAPA • JESSE MAYORGA DANIELSON Team 5 (graphics) • LEO ZEN • FRANCISCO MORALES • HIROE ONO • SIMON HUYNH • FRANCESCO MANTOVANI • MICHAEL IDRIS MERCHANT February 21, 2010 – 18:05:19 (c) 2010 University of California, Irvine – André van der Hoek 26

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