Twigs (not STIX)

http://twigs-cti.herokuapp.com

Design Goals

1. Simplicity

• Target the 80%
• Easy to implement
• Easy to understand
• One way of doing things

1. Reduce Optionality

• Support customization in a standardized way
• Don’t allow customization everywhere, only where likely to be used

1. Standardization

• Do things the same way across STIX and CybOX
• Reuse similar structures across similar yet distinct parts of the model

1. Modularity

• Provide building blocks that can be reused
• Ensuring tight cohesion and low coupling

1. Flexibility

• Use modularity to provide flexibility
• Flexibility is not as important as simplicity or reducing optionality

1. Improve Analysis

• Explicitly modeled as a graph
• Ensure data structures are separate from metadata

1. STIX 1.x compatibility (i.e., content conversion ala STIX Ramrod)

• Upconverting is a higher priority than downconverting

High-level decisions

1. Implemented in JSON and JSON Schema per the CTI TC ballot and CTI TC JSON style guide.

2. Add a CTI Common specification for high-level constructs used across all languages.

3. The Observable and Event layers are removed from CybOX, which becomes a library of CybOX objects. In STIX, the "Observation" object covers observable instances, and indicator patterning covers observable patterns. Sightings are accomplished using a relationship between an Observation and an Indicator.

4. Controlled vocabularies are limited, and where used they allow both a hardcoded enum in the STIX default vocabulary as well as an extension value in an external vocabulary.