Gateway Compression in Early Modules: Cross-Stage Downstream Blockage in the 2005 Civil Engineering Curriculum at FACET-UNT

This paper extends a prior structural audit of early-stage curricular constraint in the 2005 Civil Engineering curriculum at FACET-UNT to the full eleven-module programme. Using the official curriculum at full subject granularity and an approval-only progression rule, the study characterises how the gateway function is distributed across the curriculum and how structurally central nodes overlap in their downstream control. Nine metrics are employed: downstream node reach (DNR), downstream curricular-load reach (DLR), critical path overlap (CPO), mean distance to blocked nodes (MDB), blockage severity score (BSS), gateway depth index (GDI), stacking coefficient (SC), cumulative blockage trajectory (CBT), gateway chain length (GCL), and gateway density per module (GDM). Metrics are organised into three functional layers: primary evidence metrics (DNR, DLR), concentration and structure metrics (SC, CBT), and auxiliary descriptive metrics (GDI, GCL, GDM, MDB). This hierarchy makes explicit which measurements anchor the central claim and which contextualise it. The analysis identifies eleven gateways using a compound criterion (BSS ≥ 75th percentile and CPO > 0). All eleven are concentrated in Modules 1 to 4, with gateway density of 100% in Module 1, 80% in Module 2, 50% in Module 3, 25% in Module 4, and zero from Module 5 onward. The gateway set controls a structurally overlapping territory: the mean pairwise stacking coefficient is 0.77, 100% of pairs exceed SC = 0.5, and 74.5% exceed SC = 0.7. The cumulative blockage trajectory reaches 81.8% of downstream nodes and 84.0% of downstream curricular load after the first gateway alone, and asymptotes near 88.6% by the fourth gateway. The longest directed gateway chain is monodisciplinary: Cálculo I → Cálculo II → Cálculo III → Cálculo IV. From Module 5 onward, nodes occupy positions of maximum gateway depth (GDI ≈ 11) without themselves acting as gateways, indicating that the entire downstream curriculum operates under a stacked foundation without exercising further gateway control.