diff --git a/Rakefile b/Rakefile
index 4e754773c..a0358f82f 100644
--- a/Rakefile
+++ b/Rakefile
@@ -338,45 +338,57 @@ namespace :test do
   end
 end
 
-namespace :gen do
-  desc <<~DESC
-    Generate all certificates and profile PDFs.
-  DESC
-  task :cert_profile_pdfs do
-    puts "==================================="
-    puts "cert_profile_pdfs: Generating MC100"
-    puts "                   1st target"
-    puts "==================================="
-    Rake::Task["#{$root}/gen/certificate_doc/pdf/MC100.pdf"].invoke
-
-    puts "=================================================="
-    puts "cert_profile_pdfs: Generating MockCertificateModel"
-    puts "                   2nd target"
-    puts "=================================================="
-    Rake::Task["#{$root}/gen/certificate_doc/pdf/MockCertificateModel.pdf"].invoke
-
-    puts "==================================="
-    puts "cert_profile_pdfs: Generating RVA20"
-    puts "                   3rd target"
-    puts "==================================="
-    Rake::Task["#{$root}/gen/profile_doc/pdf/RVA20.pdf"].invoke
-
-    puts "==================================="
-    puts "cert_profile_pdfs: Generating RVA22"
-    puts "                   4th target"
-    puts "==================================="
-    Rake::Task["#{$root}/gen/profile_doc/pdf/RVA22.pdf"].invoke
-
-    puts "==================================="
-    puts "cert_profile_pdfs: Generating RVI20"
-    puts "                   5th target"
-    puts "==================================="
-    Rake::Task["#{$root}/gen/profile_doc/pdf/RVI20.pdf"].invoke
-
-    puts "==================================="
-    puts "cert_profile_pdfs: Generating MockProfileRelease"
-    puts "                   6th target"
-    puts "==================================="
-    Rake::Task["#{$root}/gen/profile_doc/pdf/MockProfileRelease.pdf"].invoke
-  end
+desc <<~DESC
+  Generate all portfolio-based PDFs (certificates and profiles).
+DESC
+task :portfolio_pdfs do
+  puts ""
+  puts "==================================="
+  puts "Generating MC100"
+  puts "==================================="
+  puts ""
+  Rake::Task["#{$root}/gen/certificate_doc/pdf/MC100.pdf"].invoke
+
+  puts ""
+  puts "=================================================="
+  puts "Generating MockCertificateModel"
+  puts "=================================================="
+  puts ""
+  Rake::Task["#{$root}/gen/certificate_doc/pdf/MockCertificateModel.pdf"].invoke
+
+  puts ""
+  puts "==================================="
+  puts "Generating RVA20"
+  puts "==================================="
+  puts ""
+  Rake::Task["#{$root}/gen/profile_doc/pdf/RVA20.pdf"].invoke
+
+  puts ""
+  puts "==================================="
+  puts "Generating RVA22"
+  puts "==================================="
+  puts ""
+  Rake::Task["#{$root}/gen/profile_doc/pdf/RVA22.pdf"].invoke
+
+  puts ""
+  puts "==================================="
+  puts "Generating RVI20"
+  puts "==================================="
+  puts ""
+  Rake::Task["#{$root}/gen/profile_doc/pdf/RVI20.pdf"].invoke
+
+  puts ""
+  puts "==================================="
+  puts "Generating MockProfileRelease"
+  puts "==================================="
+  puts ""
+  Rake::Task["#{$root}/gen/profile_doc/pdf/MockProfileRelease.pdf"].invoke
 end
+
+# Shortcut targets for building profiles and certificates.
+task MC100: "#{$root}/gen/certificate_doc/pdf/MC100.pdf"
+task MockCertificateModel: "#{$root}/gen/certificate_doc/pdf/MockCertificateModel.pdf"
+task RVI20: "#{$root}/gen/profile_doc/pdf/RVI20.pdf"
+task RVA20: "#{$root}/gen/profile_doc/pdf/RVA20.pdf"
+task RVA22: "#{$root}/gen/profile_doc/pdf/RVA22.pdf"
+task MockProfileRelease: "#{$root}/gen/profile_doc/pdf/MockProfileRelease.pdf"
diff --git a/arch/csr/menvcfg.yaml b/arch/csr/menvcfg.yaml
index 49d263d8b..8feafff95 100644
--- a/arch/csr/menvcfg.yaml
+++ b/arch/csr/menvcfg.yaml
@@ -6,7 +6,8 @@ name: menvcfg
 address: 0x30A
 long_name: Machine Environment Configuration
 description: |
-  Contains bits to enable/disable extensions
+  Contains fields that control certain characteristics of the execution environment
+  for modes less privileged than M-mode.
 
   The `menvcfg` CSR controls
   certain characteristics of the execution environment for modes less
diff --git a/arch/csr/senvcfg.yaml b/arch/csr/senvcfg.yaml
index 1c6aea47d..6feb15134 100644
--- a/arch/csr/senvcfg.yaml
+++ b/arch/csr/senvcfg.yaml
@@ -5,14 +5,15 @@ kind: csr
 name: senvcfg
 address: 0x10A
 long_name: Supervisor Environment Configuration
-description: Contains bits to enable/disable extensions
+description: |
+  Contains fields that control certain characteristics of the U-mode execution environment.
 priv_mode: S
 length: 64
 definedBy:
   allOf:
-    - name: Sm
-      version: ">=1.12"
     - name: S
+      version: ">=1.12"
+    - name: U
 fields:
   CBZE:
     location: 7
diff --git a/arch/ext/S.yaml b/arch/ext/S.yaml
index d7fecf677..6d350dcd8 100644
--- a/arch/ext/S.yaml
+++ b/arch/ext/S.yaml
@@ -6,12 +6,18 @@ name: S
 type: privileged
 long_name: Supervisor mode
 versions:
-  - version: "1.12.0"
-    state: ratified
-    ratification_date: 2021-12
-    requires:
-      name: U
-      version: "= 1.12.0"
+- version: "1.11.0"
+  state: ratified
+  ratification_date: 2019-06
+  requires:
+    name: U
+    version: "= 1.0.0"
+- version: "1.12.0"
+  state: ratified
+  ratification_date: 2021-12
+  requires:
+    name: U
+    version: "= 1.0.0"
 description: |
   This chapter describes the RISC-V supervisor-level architecture, which
   contains a common core that is used with various supervisor-level
diff --git a/arch/ext/Sm.yaml b/arch/ext/Sm.yaml
index db631b92f..53c1a78a8 100644
--- a/arch/ext/Sm.yaml
+++ b/arch/ext/Sm.yaml
@@ -460,6 +460,7 @@ params:
     schema:
       type: string
       enum: [little, big, dynamic]
+      # TODO: Only little available in Sm 1.11
   MISA_CSR_IMPLEMENTED:
     description: |
       Whether or not the `misa` CSR returns zero or a non-zero value.
diff --git a/arch/ext/Sstc.yaml b/arch/ext/Sstc.yaml
index 03f2b76e7..a662943a5 100644
--- a/arch/ext/Sstc.yaml
+++ b/arch/ext/Sstc.yaml
@@ -3,8 +3,8 @@
 $schema: "ext_schema.json#"
 kind: extension
 name: Sstc
-long_name: Superivisor mode timer interrupts
-description: Superivisor mode timer interrupts
+long_name: Supervisor-mode timer interrupts
+description: Supervisor-mode timer interrupts
 type: privileged
 versions:
   - version: "0.9.0"
diff --git a/arch/ext/Sv32.yaml b/arch/ext/Sv32.yaml
index e638dc938..6ac42cabe 100644
--- a/arch/ext/Sv32.yaml
+++ b/arch/ext/Sv32.yaml
@@ -9,5 +9,5 @@ type: privileged
 versions:
   - version: "1.12.0"
     state: ratified
-    ratification_date: unknown
+    ratification_date: null
     url: https://github.com/riscv/riscv-isa-manual/releases/download/Priv-v1.12/riscv-privileged-20211203.pdf
diff --git a/arch/ext/Sv39.yaml b/arch/ext/Sv39.yaml
index bd54871df..646c0380e 100644
--- a/arch/ext/Sv39.yaml
+++ b/arch/ext/Sv39.yaml
@@ -9,5 +9,5 @@ type: privileged
 versions:
   - version: "1.12.0"
     state: ratified
-    ratification_date: unknown
+    ratification_date: null
     url: https://github.com/riscv/riscv-isa-manual/releases/download/Priv-v1.12/riscv-privileged-20211203.pdf
diff --git a/arch/ext/Sv48.yaml b/arch/ext/Sv48.yaml
index 40b6416f6..ef7f970e5 100644
--- a/arch/ext/Sv48.yaml
+++ b/arch/ext/Sv48.yaml
@@ -9,7 +9,7 @@ type: privileged
 versions:
   - version: "1.12.0"
     state: ratified
-    ratification_date: unknown
+    ratification_date: null
     url: https://github.com/riscv/riscv-isa-manual/releases/download/Priv-v1.12/riscv-privileged-20211203.pdf
     requires:
       name: Sv39
diff --git a/arch/ext/Sv57.yaml b/arch/ext/Sv57.yaml
index 62f1d82a1..18bdd3d15 100644
--- a/arch/ext/Sv57.yaml
+++ b/arch/ext/Sv57.yaml
@@ -9,7 +9,7 @@ type: privileged
 versions:
   - version: "1.12.0"
     state: ratified
-    ratification_date: unknown
+    ratification_date: null
     url: https://github.com/riscv/riscv-isa-manual/releases/download/Priv-v1.12/riscv-privileged-20211203.pdf
     requires:
       name: Sv48
diff --git a/arch/ext/U.yaml b/arch/ext/U.yaml
index 40a7a0657..cacb07c3f 100644
--- a/arch/ext/U.yaml
+++ b/arch/ext/U.yaml
@@ -3,13 +3,15 @@
 $schema: "ext_schema.json#"
 kind: extension
 name: U
-long_name: User-level privilege mode
-description: User-level privilege mode
+long_name: User-mode privilege level
+description: |
+  User-mode privilege level is supported by an implementation if the U extension is present.
+  Note that the RISC-V ISA doens't formally define a U extension and it is only discussed in the Privileged ISA manual.
 type: privileged
 versions:
-  - version: "1.12.0"
-    state: ratified
-    ratification_date: 2019-12
+- version: "1.0.0"
+  state: ratified
+  ratification_date: 2019-12
 params:
   MUTABLE_MISA_U:
     description: |
diff --git a/arch/ext/Zihpm.yaml b/arch/ext/Zihpm.yaml
index c5922e781..f5f798b9d 100644
--- a/arch/ext/Zihpm.yaml
+++ b/arch/ext/Zihpm.yaml
@@ -9,6 +9,6 @@ type: unprivileged
 versions:
   - version: "2.0.0"
     state: ratified
-    ratification_date: unknown
+    ratification_date: null
     requires:
       name: Smhpm
diff --git a/arch/profile/MP-S-64.yaml b/arch/profile/MP-S-64.yaml
index cd34a233c..de2718e08 100644
--- a/arch/profile/MP-S-64.yaml
+++ b/arch/profile/MP-S-64.yaml
@@ -36,6 +36,9 @@ extensions:
       optional: transitory
     version: "= 1.11"
     note: Made this a transitory option
+  Xmock:
+    presence: mandatory
+    version: "~> 0.9.9"
 extra_notes:
   - presence: mandatory
     text: |
diff --git a/arch/profile/RVA20S64.yaml b/arch/profile/RVA20S64.yaml
index 7af25aa36..939b820f0 100644
--- a/arch/profile/RVA20S64.yaml
+++ b/arch/profile/RVA20S64.yaml
@@ -11,6 +11,13 @@ introduction: |
   processors.  RVA20S64 is based on privileged architecture version 1.11.
 extensions:
   $inherits: "profile/RVI20U64.yaml#/extensions"
+  U:
+    presence: mandatory
+    version: "~> 1.0"
+    param_constraints:
+      U_MODE_ENDIANESS:
+        schema:
+          const: little``
   S:
     presence: mandatory
     version: "= 1.11"
diff --git a/backends/certificate_doc/tasks.rake b/backends/certificate_doc/tasks.rake
index 3972b31f3..df4c6562c 100644
--- a/backends/certificate_doc/tasks.rake
+++ b/backends/certificate_doc/tasks.rake
@@ -25,15 +25,18 @@ Dir.glob("#{$root}/arch/certificate_model/*.yaml") do |f|
     __FILE__
   ] do |t|
     # TODO: schema validation
-    cfg_arch = cfg_arch_for("rv#{base}")
-    cert_model = cfg_arch.cert_model(cert_model_name)
-    raise "No certificate model defined for #{cert_model_name}" if cert_model.nil?
+    base_cert_model = cfg_arch_for("rv#{base}").cert_model(cert_model_name)
+    raise "No certificate model named '#{cert_model_name}'" if base_cert_model.nil?
 
-    # Switch to the generated certificate arch def
+    # Ask base certification model to create an in-memory config arch for this model.
     # XXX - Add this to profile releases
-    cfg_arch = cert_model.to_cfg_arch
+    cfg_arch = base_cert_model.to_cfg_arch
+
+    # Set globals for ERB template.
     cert_model = cfg_arch.cert_model(cert_model_name)
     cert_class = cert_model.cert_class
+    portfolio = cert_model
+    portfolio_class = cert_class
 
     version = File.basename(t.name, '.adoc').split('-')[1..].join('-')
 
diff --git a/backends/certificate_doc/templates/certificate.adoc.erb b/backends/certificate_doc/templates/certificate.adoc.erb
index 41e9fb32f..b37cf7f18 100644
--- a/backends/certificate_doc/templates/certificate.adoc.erb
+++ b/backends/certificate_doc/templates/certificate.adoc.erb
@@ -201,16 +201,11 @@ None
 
 == Instruction Summary
 
-<%
-  insts = cert_model.in_scope_extensions.map { |ext_cert_model| ext_cert_model.instructions }.flatten.uniq
-  insts.sort_by!(&:name)
--%>
-
 [%autowidth]
 |===
 | Name | Long Name
 
-<% insts.each do |inst| -%>
+<% portfolio.in_scope_instructions.each do |inst| -%>
 | <%= link_to_inst(inst.name) %>
 | <%= inst.long_name %>
 <% end # do -%>
@@ -387,12 +382,7 @@ The following instructions are added by this extension:
 [appendix]
 == Instruction Details
 
-<%=
-  insts = cert_model.in_scope_extensions.map { |ext_cert_model| ext_cert_model.instructions }.flatten.uniq
-  insts.sort_by!(&:name)
--%>
-
-<% insts.each do |inst| -%>
+<% portfolio.in_scope_instructions.each do |inst| -%>
 <<<
 <%= anchor_for_inst(inst.name) %>
 === <%= inst.name %>
diff --git a/backends/profile_doc/tasks.rake b/backends/profile_doc/tasks.rake
index 8b68ba048..26f1fb869 100644
--- a/backends/profile_doc/tasks.rake
+++ b/backends/profile_doc/tasks.rake
@@ -7,11 +7,13 @@ rule %r{#{$root}/gen/profile_doc/adoc/.*\.adoc} => [
   Dir.glob("#{$root}/arch/profile_release/**/*.yaml")
 ].flatten do |t|
   profile_release_name = Pathname.new(t.name).basename(".adoc").to_s
-
   profile_release = cfg_arch_for("_").profile_release(profile_release_name)
   raise ArgumentError, "No profile release named '#{profile_release_name}'" if profile_release.nil?
 
+  # Set globals for ERB template.
   profile_class = profile_release.profile_class
+  portfolio_class = profile_class
+  portfolio = profile_release
 
   template_path = Pathname.new "#{$root}/backends/profile_doc/templates/profile.adoc.erb"
   erb = ERB.new(template_path.read, trim_mode: "-")
diff --git a/backends/profile_doc/templates/profile.adoc.erb b/backends/profile_doc/templates/profile.adoc.erb
index 9eeef40c5..1d24b8a1c 100644
--- a/backends/profile_doc/templates/profile.adoc.erb
+++ b/backends/profile_doc/templates/profile.adoc.erb
@@ -2,7 +2,7 @@
 :description: <%= profile_release.marketing_name %> Profile
 :revdate: <%= profile_release.ratification_date.nil? ? Date.today : profile_release.ratification_date %>
 
-// XXX - Figure out what we really want here - Change percent hash to percent equals.
+// TODO - Figure out what we really want here - Change percent hash to percent equals.
 // :revnumber: <%# profile_release.map(&:version).sort.last %>
 
 :revmark: "TODO: revmark"
@@ -311,6 +311,7 @@ optional profile extensions for a new profile might be prototyped as
 non-profile extensions on an earlier profile.
 
 // XXX - Need to create render() Ruby function.
+// See https://github.com/riscv-software-src/riscv-unified-db/issues/59
 // <%# render("#{$root}/backends/portfolio_doc/templates/family_intro.erb", portfolio_class: profile_class) %>
 
 == <%= profile_class.name %> Profile Class
@@ -344,21 +345,6 @@ Ratification date:: <%= profile_release.ratification_date %>
 --
 <% end # each profile_release -%>
 
-=== Extension Presence
-
-The <%= profile_class.marketing_name %> Profile Class references
-<%= profile_class.referenced_extensions.size %> extensions.
-
-.Status
-|===
-| Extension | <%= profile_class.profiles.map(&:marketing_name).join(" | ") -%>
-
-<% profile_class.referenced_extensions.sort_by(&:name).each do |ext| -%>
-| <%= ext.name %> | <%= profile_class.profiles.map { |profile| profile.extension_presence(ext.name) }.join(" | ") -%>
-<% end -%>
-
-|===
-
 == <%= profile_release.name %> Profile Release
 
 <%= profile_release.introduction %>
@@ -370,8 +356,8 @@ associated implementation-defined parameters across all its defined profiles.
 === <%= profile_release.name %> Description
 
 <%= profile_release.description %>
-
 <% end # unless -%>
+
 <% profile_release.profiles.each do |profile| -%>
 === <%= profile.marketing_name %> Profile
 
@@ -411,6 +397,41 @@ associated implementation-defined parameters.
 
 <% end # each profile -%>
 
+<<<
+[appendix]
+== Profile Comparisons
+
+=== Release Comparison
+
+The <%= profile_class.marketing_name %> Profile Class has <%= profile_class.profile_releases.size %> releases that
+reference a total of <%= profile_class.referenced_extensions.size %> extensions.
+
+.Extension Presence
+|===
+| Extension | <%= profile_class.profile_releases.map(&:marketing_name).join(" | ") %>
+
+<% profile_class.referenced_extensions.sort_by(&:name).each do |ext| -%>
+| <%= ext.name %> | <%= profile_class.profile_releases.map { |profile_release| profile_release.extension_presence(ext.name) }.join(" | ") %>
+<% end -%>
+|===
+
+=== Profile Comparison
+
+The <%= profile_release.marketing_name %> Profile Release has <%= profile_release.profiles.size %> profiles that
+reference a total of <%= profile_release.referenced_extensions.size %> extensions.
+
+[NOTE]
+Extensions present in a profile are also present in higher-privileged profiles in the same profile release.
+
+.Extension Presence
+|===
+| Extension | <%= profile_release.profiles.map(&:marketing_name).join(" | ") %>
+
+<% profile_release.referenced_extensions.sort_by(&:name).each do |ext| -%>
+| <%= ext.name %> | <%= profile_release.profiles.map { |profile| profile.extension_presence(ext.name) }.join(" | ") %>
+<% end -%>
+|===
+
 <<<
 [appendix]
 == Extension Details
@@ -420,20 +441,24 @@ associated implementation-defined parameters.
 === <%= ext.name %> Extension
 <%= ext.long_name %>
 
-.Status
+.<%= ext.name %> Extension Presence
 |===
 | Profile | v<%= ext.versions.map { |ext_ver| ext_ver.canonical_version.to_s }.join(" | v") %>
 
 <% profile_release.profiles.each do |profile| -%>
-| <%= profile.marketing_name %> | <%= profile.version_strongest_presence(ext.name, ext.versions).join(" | ") -%>
+| <%= profile.marketing_name %> | <%= profile.version_greatest_presence(ext.name, ext.versions).join(" | ") -%>
 <% end -%>
 
 |===
 
 <% ext.versions.each do |v| -%>
 <%= v.canonical_version %>::
+  State:::
+    <%= v.state %>
+  <% if v.state == "ratified" -%>
   Ratification date:::
     <%= v.ratification_date %>
+  <% end # if %>
   <% unless v.changes.empty? -%>
   Changes:::
 
@@ -441,18 +466,18 @@ associated implementation-defined parameters.
     * <%= c %>
     <% end -%>
 
-  <%- end -%>
-  <%- unless v.url.nil? -%>
+  <% end -%>
+  <% unless v.url.nil? -%>
   Ratification document:::
     <%= v.url %>
-  <%- end -%>
-  <%- unless v.implications -%>
+  <% end -%>
+  <% unless v.implications -%>
   Implies:::
-    <%- v.implications.each do |i| -%>
+    <% v.implications.each do |i| -%>
     * `<%= i.name %>` version <%= i.version %>
-    <%- end -%>
-  <%- end -%>
-<%- end -%>
+    <% end -%>
+  <% end -%>
+<% end -%>
 
 ==== Synopsis
 
diff --git a/cfgs/generic_rv64/cfg.yaml b/cfgs/generic_rv64/cfg.yaml
index c15ff4800..7577c8bd3 100644
--- a/cfgs/generic_rv64/cfg.yaml
+++ b/cfgs/generic_rv64/cfg.yaml
@@ -16,7 +16,7 @@ implemented_extensions:
   - [Sm, "1.12.0"]
   - [Smhpm, "1.12.0"]
   - [Smpmp, "1.12.0"]
-  - [U, "1.12.0"]
+  - [U, "1.0.0"]
   - [V, "1.0.0"]
   - [Zicntr, "2.0.0"]
   - [Zicsr, "2.0.0"]
diff --git a/do b/do
index 8d18a10eb..92ed0e671 100755
--- a/do
+++ b/do
@@ -9,6 +9,5 @@ fi
 
 source $ROOT/bin/setup
 
-
 # really long way of invoking rake, but renamed to 'do'
 $BUNDLE exec --gemfile $ROOT/Gemfile ruby -r rake -e "Rake.application.init('do');Rake.application.load_rakefile;Rake.application.top_level" -- $@
diff --git a/lib/arch_obj_models/certificate.rb b/lib/arch_obj_models/certificate.rb
index d422ea6c5..80856b6f3 100644
--- a/lib/arch_obj_models/certificate.rb
+++ b/lib/arch_obj_models/certificate.rb
@@ -69,7 +69,7 @@ def when_pretty
             "Parameter #{param_name} == #{param_value}"
           end
         else
-          raise "TODO: when type #{key} not implemented"
+          raise "Type #{key} not implemented"
         end
       end.flatten.join(" and ")
     end
@@ -103,7 +103,7 @@ def when_pretty
             "Parameter #{param_name} == #{param_value}"
           end
         else
-          raise "TODO: when type #{key} not implemented"
+          raise "Type #{key} not implemented"
         end
       end.flatten.join(" and ")
     end
diff --git a/lib/arch_obj_models/extension.rb b/lib/arch_obj_models/extension.rb
index 54d4d23fa..d1f97c6b8 100644
--- a/lib/arch_obj_models/extension.rb
+++ b/lib/arch_obj_models/extension.rb
@@ -6,7 +6,7 @@
 
 # A parameter (AKA option, AKA implementation-defined value) supported by an extension
 class ExtensionParameter
-  # @return [ConfiguredArchitecture] The defining Arch def
+  # @return [ConfiguredArchitecture] The defining configured architecture
   attr_reader :cfg_arch
 
   # @return [String] Parameter name
@@ -293,14 +293,14 @@ def initialize(name, version_str, cfg_arch, fail_if_version_does_not_exist: fals
     @cfg_arch = cfg_arch
 
     @ext = @cfg_arch.extension(@name)
-    raise "Extension #{name} not found in arch def" if @ext.nil?
+    raise "Extension #{name} not found in configured architecture #{cfg_arch.name}" if @ext.nil?
 
     @data = @ext.data["versions"].find { |v| VersionSpec.new(v["version"]) == @version_spec }
 
     if fail_if_version_does_not_exist && @data.nil?
-      raise ArgumentError, "#{@name}, Version #{version_str} is not defined"
+      raise ArgumentError, "Version #{version_str} of #{@name} extension in #{cfg_arch.name} is not defined"
     elsif @data.nil?
-      warn "#{@name}, Version #{version_str} is not defined"
+      warn "Version #{version_str} of #{@name} extension in #{cfg_arch.name} is not defined"
     end
   end
 
@@ -558,8 +558,8 @@ def initialize(data)
     end
   end
 
-  def mandatory? = (@presence == mandatory)
-  def optional? = (@presence == optional)
+  def mandatory? = (@presence == "mandatory")
+  def optional? = (@presence == "optional")
 
   # Class methods
   def self.mandatory = "mandatory"
@@ -604,6 +604,10 @@ def to_s
     @optional_type.nil? ? "#{presence}" : "#{presence} (#{optional_type})"
   end
 
+  def to_s_concise
+    "#{presence}"
+  end
+
   # @overload ==(other)
   #   @param other [String] A presence string
   #   @return [Boolean] whether or not this ExtensionPresence has the same presence (ignores optional_type)
@@ -621,15 +625,43 @@ def ==(other)
     end
   end
 
-  # Sorts by presence, then by optional_type
-  def <=>(other)
+  ######################################################
+  # Following comparison operators follow these rules:
+  #   - "mandatory" is greater than "optional"
+  #   - optional_types all have same rank
+  #   - equals compares presence and then optional_type
+  ######################################################
+
+  # @overload >(other)
+  #   @param other [ExtensionPresence] An extension presence object
+  #   @return [Boolean] Whether or not this ExtensionPresence is greater-than the other
+  def >(other)
     raise ArgumentError, "ExtensionPresence is only comparable to other ExtensionPresence classes" unless other.is_a?(ExtensionPresence)
+    (self.mandatory? && other.optional?)
+  end
 
-    if @presence != other.presence
-      @presence <=> other.presence
-    else
-      @optional_type <=> other.optional_type
-    end
+  # @overload >=(other)
+  #   @param other [ExtensionPresence] An extension presence object
+  #   @return [Boolean] Whether or not this ExtensionPresence is greater-than or equal to the other
+  def >=(other)
+    raise ArgumentError, "ExtensionPresence is only comparable to other ExtensionPresence classes" unless other.is_a?(ExtensionPresence)
+    (self > other) || (self == other)
+  end
+
+  # @overload <(other)
+  #   @param other [ExtensionPresence] An extension presence object
+  #   @return [Boolean] Whether or not this ExtensionPresence is less-than the other
+  def <(other)
+    raise ArgumentError, "ExtensionPresence is only comparable to other ExtensionPresence classes" unless other.is_a?(ExtensionPresence)
+    (self.optional? && other.mandatory?)
+  end
+
+  # @overload <=(other)
+  #   @param other [ExtensionPresence] An extension presence object
+  #   @return [Boolean] Whether or not this ExtensionPresence is less-than or equal to the other
+  def <=(other)
+    raise ArgumentError, "ExtensionPresence is only comparable to other ExtensionPresence classes" unless other.is_a?(ExtensionPresence)
+    (self < other) || (self == other)
   end
 end
 
@@ -650,8 +682,12 @@ class ExtensionRequirement
   # @return [Array<RequirementSpec>] Set of requirement specifications
   def requirement_specs = @requirements
 
+  def requirement_specs_to_s
+    "#{@requirements.map(&:to_s).join(', ')}"
+  end
+
   def to_s
-    "#{name} #{@requirements.map(&:to_s).join(', ')}"
+    "#{name} " + requirement_specs_to_s
   end
 
   # @return [Extension] The extension that this requirement is for
@@ -673,7 +709,7 @@ def initialize(name, *requirements, cfg_arch: nil, note: nil, req_id: nil, prese
     @cfg_arch = cfg_arch
     @ext = @cfg_arch.extension(@name)
 
-    raise ArgumentError, "Could not find extension named '#{@name}'" if @ext.nil?
+    raise ArgumentError, "Could not find extension named '#{@name}' in #{@cfg_arch.name}" if @ext.nil?
 
     requirements =
       if requirements.empty?
@@ -721,7 +757,7 @@ def satisfied_by?(*args)
           end
         end
       else
-        raise ArgumentError, "Single argument must be an ExtensionVersion or ExtensionRquirement"
+        raise ArgumentError, "Single argument must be an ExtensionVersion or ExtensionRequirement"
       end
     elsif args.size == 2
       raise ArgumentError, "First parameter must be an extension name" unless args[0].respond_to?(:to_s)
diff --git a/lib/arch_obj_models/portfolio.rb b/lib/arch_obj_models/portfolio.rb
index 0afa26720..2ee8f2169 100644
--- a/lib/arch_obj_models/portfolio.rb
+++ b/lib/arch_obj_models/portfolio.rb
@@ -49,36 +49,49 @@ def description = @data["description"]
   # @return [Gem::Version] Semantic version of the PortfolioInstance
   def version = Gem::Version.new(@data["version"])
 
+  # @return [ExtensionPresence] Given an extension +ext_name+, return the presence.
+  #                             If the extension name isn't found in the portfolio, return nil.
+  def extension_presence_obj(ext_name)
+    # Get extension information from YAML for passed in extension name.
+    ext_data = @data["extensions"][ext_name]
+
+    ext_data.nil? ? nil : ExtensionPresence.new(ext_data["presence"])
+  end
+
   # @return [String] Given an extension +ext_name+, return the presence as a string.
   #                  If the extension name isn't found in the portfolio, return "-".
   def extension_presence(ext_name)
-    # Get extension information from YAML for passed in extension name.
-    ext_data = @data["extensions"][ext_name]
+    ext_presence_obj = extension_presence_obj(ext_name)
 
-    ext_data.nil? ? "-" : ExtensionPresence.new(ext_data["presence"]).to_s
+    ext_presence_obj.nil? ? "-" : ext_presence_obj.to_s
   end
 
-  # Returns the strongest presence string for each of the specified versions.
+  # Returns the greatest presence string for each of the specified versions.
   # @param ext_name [String]
   # @param ext_versions [Array<ExtensionVersion>]
   # @return [Array<String>]
-  def version_strongest_presence(ext_name, ext_versions)
+  def version_greatest_presence(ext_name, ext_versions)
     presences = []
 
     # See if any extension requirement in this profile lists this version as either mandatory or optional.
     ext_versions.map do |v|
-      mandatory = mandatory_ext_reqs.any? { |ext_req| ext_req.satisfied_by?(v) }
-      optional = optional_ext_reqs.any? { |ext_req| ext_req.satisfied_by?(v) }
-
-      # Just show strongest presence (mandatory stronger than optional).
-      presences <<
-        if mandatory
-          ExtensionPresence.mandatory
-        elsif optional
-          ExtensionPresence.optional
-        else
-          "-"
+      greatest_presence = nil
+
+      in_scope_ext_reqs.each do |ext_req|
+        if ext_req.satisfied_by?(v)
+          presence = extension_presence_obj(ext_name)
+
+          unless presence.nil?
+            if greatest_presence.nil?
+              greatest_presence = presence
+            elsif presence > greatest_presence
+              greatest_presence = presence
+            end
+          end
         end
+      end
+
+      presences << (greatest_presence.nil? ? "-" : greatest_presence.to_s_concise)
     end
 
     presences
@@ -108,13 +121,23 @@ def in_scope_ext_reqs(desired_presence = nil)
       desired_presence.is_a?(ExtensionPresence) ? desired_presence :
       ExtensionPresence.new(desired_presence)
 
+    missing_ext = false
+
     @data["extensions"]&.each do |ext_name, ext_data|
       next if ext_name[0] == "$"
 
+      # Does extension even exist?
+      # If not, don't raise an error right away so we can find all of the missing extensions and report them all.
+      ext = cfg_arch.extension(ext_name)
+      if ext.nil?
+        puts "Extension #{ext_name} for #{name} not found in database"
+        missing_ext = true
+      end
+
       actual_presence = ext_data["presence"]    # Could be a String or Hash
       raise "Missing extension presence for extension #{ext_name}" if actual_presence.nil?
 
-      # Convert String or Hash to object.
+      # Convert presence String or Hash to object.
       actual_presence_obj = ExtensionPresence.new(actual_presence)
 
       match =
@@ -137,6 +160,11 @@ def in_scope_ext_reqs(desired_presence = nil)
           end
       end
     end
+
+    # TODO: Change to "raise" when missing extensions added to database so we can make progress until then.
+    # See https://github.com/riscv-software-src/riscv-unified-db/issues/320
+    puts "One or more extensions referenced by #{name} missing in database" if missing_ext
+
     in_scope_ext_reqs
   end
 
@@ -148,19 +176,20 @@ def optional_type_ext_reqs = in_scope_ext_reqs(ExtensionPresence.optional)
   def in_scope_extensions
     return @in_scope_extensions unless @in_scope_extensions.nil?
 
-    @in_scope_extensions = in_scope_ext_reqs.map do |er|
-      obj = cfg_arch.extension(er.name)
-
-      # @todo: change this to raise once all the profile extensions
-      #        are defined
-      warn "Extension #{er.name} is not defined" if obj.nil?
-
-      obj
-    end.reject(&:nil?)
+    @in_scope_extensions = in_scope_ext_reqs.map do |ext_req|
+      cfg_arch.extension(ext_req.name)
+    end.reject(&:nil?)  # Filter out extensions that don't exist yet.
 
     @in_scope_extensions
   end
 
+  # @return [Array<Instruction>] Sorted list of all instructions associated with extensions listed as
+  #                              mandatory or optional in portfolio. Uses minimum version of
+  #                              extension version that meets extension requirement specified in portfolio.
+  def in_scope_instructions
+    in_scope_extensions.map { |ext| ext.instructions }.flatten.uniq.sort
+  end
+
   # @return [Boolean] Does the profile differentiate between different types of optional.
   def uses_optional_types?
     return @uses_optional_types unless @uses_optional_types.nil?
@@ -178,6 +207,9 @@ def uses_optional_types?
     @uses_optional_types
   end
 
+  # Called by rakefile when generating a particular portfolio instance.
+  # Creates an in-memory data structure used by all portfolio routines that access a cfg_arch.
+  #
   # @return [ConfiguredArchitecture] A partially-configured architecture definition corresponding to this portfolio.
   def to_cfg_arch
     return @generated_cfg_arch unless @generated_cfg_arch.nil?
@@ -198,7 +230,7 @@ def to_cfg_arch
       "params" => all_in_scope_ext_params.select(&:single_value?).map { |p| [p.name, p.value] }.to_h
     }
 
-    # XXX Add list of prohibited_extensions
+    # TODO: Add list of prohibited_extensions
 
     @generated_cfg_arch =
       Dir.mktmpdir do |dir|
diff --git a/lib/arch_obj_models/profile.rb b/lib/arch_obj_models/profile.rb
index 1149689c8..4e7e4910e 100644
--- a/lib/arch_obj_models/profile.rb
+++ b/lib/arch_obj_models/profile.rb
@@ -111,6 +111,27 @@ def referenced_extensions
 
     @referenced_extensions
   end
+
+  # @return [String] Given an extension +ext_name+, return the presence as a string.
+  #                  Returns the greatest presence string across all profiles in the release.
+  #                  If the extension name isn't found in the release, return "-".
+  def extension_presence(ext_name)
+    greatest_presence = nil
+
+    profiles.each do |profile|
+      presence = profile.extension_presence_obj(ext_name)
+
+      unless presence.nil?
+        if greatest_presence.nil?
+          greatest_presence = presence
+        elsif presence > greatest_presence
+          greatest_presence = presence
+        end
+      end
+    end
+
+    greatest_presence.nil? ? "-" : greatest_presence.to_s_concise
+  end
 end
 
 # Representation of a specific profile in a profile release.
@@ -204,7 +225,7 @@ def ext_req_to_adoc(ext_req)
     ext = cfg_arch.extension(ext_req.name)
     ret << "* *#{ext_req.name}* " + (ext.nil? ? "" : ext.long_name)
     ret << "+"
-    ret << "Version #{ext_req.requirement_specs}"
+    ret << "Version #{ext_req.requirement_specs_to_s}"
 
     ret
   end
diff --git a/lib/arch_obj_models/schema.rb b/lib/arch_obj_models/schema.rb
index 041e1da7c..ff11d6b94 100644
--- a/lib/arch_obj_models/schema.rb
+++ b/lib/arch_obj_models/schema.rb
@@ -107,7 +107,7 @@ def to_pretty_s(schema_hash = @schema_hash)
           raise "to_pretty_s unknown type #{schema_hash["type"]} in #{schema_hash}"
         end
       else
-        raise "TODO: to_pretty_s schema for #{schema_hash}"
+        raise "Unsupported schema for #{schema_hash}"
       end
     end
 
diff --git a/lib/idl/tests/helpers.rb b/lib/idl/tests/helpers.rb
index 3b3132d5d..2d694e5b3 100644
--- a/lib/idl/tests/helpers.rb
+++ b/lib/idl/tests/helpers.rb
@@ -3,23 +3,23 @@
 require "ostruct"
 
 # Extension mock that returns an extension name
-class MockExtension
+class Xmockension
   attr_reader :name
   def initialize(name)
     @name = name
   end
 end
 
-MockExtensionParameter = Struct.new(:name, :desc, :schema, :extra_validation, :exts, :type)
-MockExtensionParameterWithValue = Struct.new(:name, :desc, :schema, :extra_validation, :exts, :value)
+XmockensionParameter = Struct.new(:name, :desc, :schema, :extra_validation, :exts, :type)
+XmockensionParameterWithValue = Struct.new(:name, :desc, :schema, :extra_validation, :exts, :value)
 
 # ConfiguredArchitecture mock that knows about XLEN and extensions
 class MockConfiguredArchitecture
   def param_values = { "XLEN" => 32 }
-  def params_with_value = [MockExtensionParameterWithValue.new("XLEN", "mxlen", {"type" => "integer", "enum" => [32, 64]}, nil, nil, 32)]
+  def params_with_value = [XmockensionParameterWithValue.new("XLEN", "mxlen", {"type" => "integer", "enum" => [32, 64]}, nil, nil, 32)]
   def params_without_value = []
   def params = []
-  def extensions = [MockExtension.new("I")]
+  def extensions = [Xmockension.new("I")]
   def mxlen = 64
   def exception_codes = [OpenStruct.new(var: "ACode", num: 0), OpenStruct.new(var: "BCode", num: 1)]
   def interrupt_codes = [OpenStruct.new(var: "CoolInterrupt", num: 1)]