Zero Defect Software Development

By John Greenland, LDRA Technology

Overview
Zero Defect Software Development (ZDSD) is a results-oriented process that emphasizes the analysis, testing, and reporting of the causes of defects. It evolved from the commitment to providing “five-nines” (99.999%) reliability for mission critical applications. It supplants the traditional approach of reacting to undesirable effects and treating symptoms while trying to manage verification using trend analyses or simply tracking the occurrences of defects.

Under ZDSD, the first step is to map system specifications and requirements to design, implementation, and verification artifacts and foster requirements-based development. This process encourages the prevention or early stage detection of defects by facilitating requirements validation and verification, design verification, and source code standardization.

ZDSD offers two major advantages:

• Higher quality software products
• Lower overall costs

ZDSD Context Model
A typical ZDSD context model has five levels: 

• Level 1: High-Level Requirements describes the system to be developed and the criteria it must meet.
• Level 2: Low-Level Requirements represents the design of the system characterized by Level 1. This level must establish links or traceability with Level 1 and constitutes a Requirements Traceability Matrix (RTM).
• Level 3: Implementation includes the production of code in accordance with Level 2.
• Level 4: Host Tier Verification is the first level dedicated to verification. It allows for the testing of embedded software modules as functional and structural entities.
• Level 5: Target Tier Verification verifies embedded software functionality. Such functionality frequently crosses hardware/software boundaries, making defect resolution more challenging.

ZDSD Solution
The ZDSD Solution is an iterative model for software development. A requirements traceability tool provides the Requirements Traceability Matrix (RTM) across all five levels of the context model. This tool supports the importation of requirements from a requirements management tool or facilitates the joining of requirements into a design modeling tool.

The requirements traceability tools must include integration with a static and dynamic analysis tool that facilitates the Code Review and Quality Review in support of Level 3 (Implementation), as well as externally performed system test code coverage analysis. Additionally, the requirements traceability tool should include integration with a unit test tool that supports software testing as described at model Levels 4 and 5. A key point is that ZDSD requires an entire set of fully integrated tools that cover the entire development process.

Conclusion
ZDSD is a largely automated yet agile process that links all stakeholders (customers, development and verification teams, and business operations) in a cohesive entity focused on measurable results. ZDSD maintains that requirements must be thoroughly and consistently verified to minimize, if not eradicate, defects while producing software products that add demonstrable value at the lowest possible cost over their entire lifecycle.

To fail to implement a software quality program leaves you open to major defects appearing during field operations. A well-defined and fully integrated program such as ZDSD is essential to avoiding catastrophic problems.

John Greenland is VP Business Development for LDRA Technology. You can reach him at john.greenland@ldra.com.