A boundary in Alexander's sense is where two light cones meet, defining separation and presence between spaces.

Entities in the same semantic neighborhood but without a typed relation to this one — candidates for new edges or unrecognized duplicates.

• "The boundary is the medium through which all evidence flows, but it is not itself evidenceable."quote0.790
  Pithy statement of the core impossibility result in its first-person experiential implication
• Life (Alexander's sense)concept0.778
  A broad notion of life that includes non-biological systems like waves and fire, central to Alexander's later philosophy.
• Alexander's experiments showed different people can agree on which actions are more structure-preserving or life-bearingfinding0.777
  Repeated experiments demonstrating that people of good will can reach substantial agreement about the life of a design decision.
• The build-to-delegable-boundary pattern is itself an Alexander Boundaries claim—boundaries protect centers.claim0.773
• Boundaries and hairlines, by both separating and uniting adjacent colors, intensify the light and form larger wholes.claim0.769
• Sycophancy is negative space — filler text that fails Alexander's principle of all space being shaped.claim0.764
• The boundary between agent and environment is not a physical object discovered in the world but a modelling choiceclaim0.763
  Established via Zanardi (2002) and the Hamiltonian decomposition argument in §2.1; foundational for the emptiness formalisation
• Alexander’s semi-lattice diagram adequately represents the relationships of complex organisms, like the urban space of the pre-industrial city with its overlapping uses.claim0.761
  Claim that the semi-lattice overcomes the reductionism of tree diagrams, capturing real urban complexity.