SOFTWARE REUSE28 March 2013 William W. McMillan

What is the most common form of software reuse in Java programming?

Benefits of Reuse

Save resources. Standardize a solution that can be

trusted. Support levels-of-abstraction approach

to creating systems. Encapsulated “black-box” components.

Reduce tedium, allow developers to work on new things.

Risks of Reuse

Propagate inefficient solution. e.g., O(N2) sorting routine

Propagate incorrect solution. Stats formula could be wrong or

inappropriate. Shield developers from fundamental

knowledge of how something works. May not know inefficiencies of solution in

particular context. May miss interactions and dependencies.

Risks of Reuse

Hard to change or update reused component.

Long-term cost if there’s a license fee. Loss of support if provider goes belly-up.

Suppose a method to compute a standard error of the mean is incorrect. What are some potential costs if the routine is used repeatedly?

History of Reuse

Copy someone’s source code to do a task. Subroutines:

Well-defined modules, with name, … but might use common data structures.

Call subroutines with parameters. “Include” files. External libraries of useful routines.

E.g., LINPACK for linear algebra and related. Database tools like Ingres

History of Reuse

Computer simulation led to object-oriented design. Simula 67

Packages and “Units” appeared. UCSD Pascal, Ada.

Abstract data types influential in computer science.

Object-oriented goes mainstream: C++, O-O capabilities bolted onto C. Smalltalk from a more AI perspective.

History of Reuse

Java cleans up a lot of O-O trash: Multiple inheritance gone. No “friend” access. Better dynamic memory management.

C# is Microsoft’s version of Java. Packages, APIs, components now

common. A lot of development is done on top of:

Statistics packages SQL engines Enterprise mega-packages like SAP

How have people employed books and tutorials on programming and scripting in software reuse?

Reuse of Software Ideas

Algorithms and data structures. Useful architectures and design patterns

(discussed earlier in course). E.g., model-view-controller

Programming styles. Elements of Programming Style by

Kernighan and Plauger Relational databases.

What benefits do you gain in being familiar with the idea of a sparse matrix?

Software Frameworks

Integrated sets of tools and utilities. E.g., .NET, Enterprise Java Beans, Allegro

Common Lisp. User interface objects and methods. Communication facilities. Security tools. Data structures. Database management. Web applications. Session and transaction management.

What facilities do you rely on most in a software framework you use?

Families of Software Products E.g., Microsoft Office, Adobe Creative

Suite. Might have unique scripting language. UI has similar feel and style across

members. Compatible parts. Common architecture. Common data formats. Incentives to use all or none. Reasons to keep all parts up to date.

Do Oracle software products constitute a family?

Buy Commercial Software?

E.g., SAP, E-Commerce tools. Why reinvent the wheel? Why not get expert advice and help? Reduce costs, especially maintenance. Reduce liability. Get things you might not have thought

of: Encryption, back-up facilities, slick

algorithms,…

Use Open-Source Software?

Talk about saving costs…. But do you always save? Where does support come from?

“Read the source code” isn’t always the help you need.

Need to consider long-term costs and risks.

When would you advise a client to consider including open-source software in a system?

Use Cloud-Based Services?

E.g., Amazon, AT&T. Third-party provider. Data and functions on servers managed

by provider. Includes many tools. Access via the Internet.

A client says, “I want this to be a cloud-based system.” What questions would you ask in order to respond intelligently?