diff --git a/.gitmodules b/.gitmodules
index 938e1f3..e1b8fe4 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -14,6 +14,10 @@
 	path = dependencies/CASE-unstable-2.0.0
 	url = https://github.com/casework/CASE-Archive.git
 	branch = unstable-2.0.0
+[submodule "dependencies/CDO-Shapes-BFO"]
+	path = dependencies/CDO-Shapes-BFO
+	url = https://github.com/Cyber-Domain-Ontology/CDO-Shapes-BFO.git
+	branch = main
 [submodule "dependencies/CDO-Shapes-Time"]
 	path = dependencies/CDO-Shapes-Time
 	url = https://github.com/Cyber-Domain-Ontology/CDO-Shapes-Time.git
diff --git a/Makefile b/Makefile
index 8469686..e8d9d61 100644
--- a/Makefile
+++ b/Makefile
@@ -61,6 +61,11 @@ all: \
 	$(MAKE) \
 	  --directory dependencies/CASE-unstable-2.0.0 \
 	  .git_submodule_init.done.log
+	# CDO-Shapes-BFO
+	test -r dependencies/CDO-Shapes-BFO/README.md \
+	  || git submodule update --init dependencies/CDO-Shapes-BFO
+	test -r dependencies/CDO-Shapes-BFO/README.md \
+	  || (echo "ERROR:Makefile:CDO-Shapes-BFO submodule README.md file not found, even though CDO-Shapes-BFO submodule initialized." >&2 ; exit 2)
 	# CDO-Shapes-Time
 	test -r dependencies/CDO-Shapes-Time/README.md \
 	  || git submodule update --init dependencies/CDO-Shapes-Time
diff --git a/dependencies/CDO-Shapes-BFO b/dependencies/CDO-Shapes-BFO
new file mode 160000
index 0000000..1ce7386
--- /dev/null
+++ b/dependencies/CDO-Shapes-BFO
@@ -0,0 +1 @@
+Subproject commit 1ce73867dfcc132a1465a578d2a5d591c76f8462
diff --git a/examples/illustrations/existence_intervals/postvisit.mk b/examples/illustrations/existence_intervals/postvisit.mk
index 4e3bcb6..0145b87 100644
--- a/examples/illustrations/existence_intervals/postvisit.mk
+++ b/examples/illustrations/existence_intervals/postvisit.mk
@@ -18,6 +18,9 @@ SHELL := /bin/bash
 
 top_srcdir := $(shell cd ../../.. ; pwd)
 
+bfo_ttl := $(top_srcdir)/dependencies/CDO-Shapes-BFO/dependencies/BFO.ttl
+sh_bfo_ttl := $(top_srcdir)/dependencies/CDO-Shapes-BFO/shapes/sh-bfo.ttl
+
 gufo_ttl := $(top_srcdir)/dependencies/CDO-Shapes-gufo/dependencies/gufo.ttl
 sh_gufo_ttl := $(top_srcdir)/dependencies/CDO-Shapes-gufo/shapes/sh-gufo.ttl
 
@@ -27,7 +30,9 @@ sh_time_ttl := $(top_srcdir)/dependencies/CDO-Shapes-Time/shapes/sh-time.ttl
 all:
 
 .cdo-shapes.done.log: \
+  $(bfo_ttl) \
   $(gufo_ttl) \
+  $(sh_bfo_ttl) \
   $(sh_gufo_ttl) \
   $(sh_time_ttl) \
   $(time_ttl) \
@@ -35,7 +40,9 @@ all:
   existence_intervals.json
 	source $(top_srcdir)/venv/bin/activate \
 	  && case_validate \
+	    --ontology-graph $(bfo_ttl) \
 	    --ontology-graph $(gufo_ttl) \
+	    --ontology-graph $(sh_bfo_ttl) \
 	    --ontology-graph $(sh_gufo_ttl) \
 	    --ontology-graph $(sh_time_ttl) \
 	    --ontology-graph $(time_ttl) \