Software Product Lines

Intro

• SW architecture is a big investment of time and effort usually by senior talent.
• Maximize this return by reusing an architecture across multiple systems.
• SW product line is a set of sw intensive systems sharing a common, managed set of features that satisfy the specific needs of a particular market segment or mission. And are developed from a common set of core assets in a prescribed way.
• Many products similar - planned rather than by accident.
• Select components from a set of core assets.
• Tailor assets - the mechanism is pre-planned. (e.g. parameterise)
• Assemble rather than generate.
• SW product lines simplify the creation of systems built specifically for customers or customer groups.

Core Assets

• The essence of a sw product line is the disciplined, strategic reuse of assets.
• Any artefact can be reused as an asset:
  • Requirements - Most of req's are common with earlier systems.
  • Arch. Design - Most imp design step already done.
  • Software components - Not just code reuse. Design processes, design successes reused.
  • Performance and modeling analysis - Perf models, schedulability analysis, distributed system issues.
  • Testing - Test plans, processes, cases, test data, harnesses etc.
  • Project planning - Budgeting, scheduling from pervious experience. Team size, composition.
  • Processes, methods and tools - Config control procedures and facilities, tools, coding standards.
  • People - transferred within projects.
  • Exemplar systems - Deployed products serve as high quality demo prototypes.
  • Defect elimination - Each new system takes adv of defect elimination of its forebears.

• Reuse nomrally difficult. SW product lines make reuse work by establishing a very strict context for it.
• Nothing is placed in the core asset library which was not built to be reused.

SW product lines are not

• Fortuitous small scale reuse. For e.g. algorithms, libraries, objects.
• Component or service based redevelopment - selecting components with no architecture focus.
• Just versions of a single product.
• Just a configurable architecture - much more than that.
• Just a set of technical standards - constraining choices without an arch. based strategy.

Benefits and risks of product line

Benefits

• Decreased cost
• Decreased labour needs
• Decreased time to market
• Increased productivity
• Improved quality
• Ability to move into new markets

Risks

• Is SPL appropriate ? Does it match the market ? Do products have sufficient commonality ?
• Substantial up front cost in establishing core assets.
• Does SPL match organisation structure ?

Core Product Line Activities

1. Core Asset Development.
2. Product Development.
3. Technical and Organisational Management.

• The order in which the above can be applied varies.
• Build products from assets - Proactive approach.
• Extract assets from products - Reactive approach.
• Product development might create new, or refine core assets.

Core Asset Development

• Inputs:
  • Product Constraints.
  • Styles, patterns and frameworks.
  • Production constraints.
  • Production strategy.

• Outputs:
  • Product line scope
  • Core assets
  • Production plan

Product Development

• Inputs:
  • Product requirements
  • Product line scope - Does the product fit within the scope ?
  • Core assets
  • Production plan - How the core assets are to be used to build the product.

• Outputs:
  • Products.
  • New assets.
  • Product constraints.