diff --git a/api/src/main/groovy/com/jessebrault/ssg/property/CollectionProperty.groovy b/api/src/main/groovy/com/jessebrault/ssg/property/CollectionProperty.groovy
new file mode 100644
index 0000000..aefbe29
--- /dev/null
+++ b/api/src/main/groovy/com/jessebrault/ssg/property/CollectionProperty.groovy
@@ -0,0 +1,5 @@
+package com.jessebrault.ssg.property
+
+interface CollectionProperty<T> extends Property<T> {
+    // TODO
+}
\ No newline at end of file
diff --git a/api/src/main/groovy/com/jessebrault/ssg/property/MapProperty.groovy b/api/src/main/groovy/com/jessebrault/ssg/property/MapProperty.groovy
new file mode 100644
index 0000000..4a0763e
--- /dev/null
+++ b/api/src/main/groovy/com/jessebrault/ssg/property/MapProperty.groovy
@@ -0,0 +1,7 @@
+package com.jessebrault.ssg.property
+
+interface MapProperty<K, V> extends Property<Map<K, V>> {
+    V get(K key)
+    void put(K key, V value)
+    void putAll(Map<? extends K, ? extends V> map)
+}
diff --git a/api/src/main/groovy/com/jessebrault/ssg/property/Properties.groovy b/api/src/main/groovy/com/jessebrault/ssg/property/Properties.groovy
index 9048902..f4f8811 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/property/Properties.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/property/Properties.groovy
@@ -14,6 +14,21 @@ final class Properties {
         new SimpleProperty<>(convention, t)
     }
 
+    static <K, V> MapProperty<K, V> getMap() {
+        new SimpleMapProperty<K, V>()
+    }
+
+    static <K, V> MapProperty<K, V> getMap(Map<? extends K, ? extends V> convention) {
+        new SimpleMapProperty<K, V>(convention)
+    }
+
+    static <K, V> MapProperty<K, V> getMap(
+            Map<? extends K, ? extends V> convention,
+            Map<? extends K, ? extends V> value
+    ) {
+        new SimpleMapProperty<K, V>(convention, value)
+    }
+
     private Properties() {}
 
 }
diff --git a/api/src/main/groovy/com/jessebrault/ssg/property/SimpleMapProperty.groovy b/api/src/main/groovy/com/jessebrault/ssg/property/SimpleMapProperty.groovy
new file mode 100644
index 0000000..7f348b3
--- /dev/null
+++ b/api/src/main/groovy/com/jessebrault/ssg/property/SimpleMapProperty.groovy
@@ -0,0 +1,122 @@
+package com.jessebrault.ssg.property
+
+import com.jessebrault.ssg.provider.CollectionProvider
+import com.jessebrault.ssg.provider.Provider
+import groovy.transform.EqualsAndHashCode
+import groovy.transform.NullCheck
+import groovy.transform.PackageScope
+
+import java.util.function.Function
+import java.util.function.UnaryOperator
+
+@PackageScope
+@NullCheck
+@EqualsAndHashCode(includeFields = true)
+final class SimpleMapProperty<K, V> implements MapProperty<K, V> {
+
+    private final Map<K, V> convention = [:]
+    private final Map<K, V> m = [:]
+
+    SimpleMapProperty(
+            Map<? extends K, ? extends V> convention,
+            Map<? extends K, ? extends V> m
+    ) {
+        this.convention.putAll(convention)
+        this.m.putAll(m)
+    }
+
+    SimpleMapProperty(Map<? extends K, ? extends V> convention) {
+        this(convention, [:] as Map<K, V>)
+    }
+
+    SimpleMapProperty() {}
+
+    @Override
+    V get(K key) {
+        if (m[key] != null) {
+            m[key]
+        } else if (convention[key] != null) {
+            convention[key]
+        } else {
+            throw new NullPointerException("no such key: ${ key }")
+        }
+    }
+
+    @Override
+    void put(K key, V value) {
+        this.m.put(key, value)
+    }
+
+    @Override
+    void putAll(Map<? extends K, ? extends V> map) {
+        this.m.putAll(map)
+    }
+
+    @Override
+    void set(Map<K, V> kvMap) {
+        this.m.clear()
+        this.m.putAll(kvMap)
+    }
+
+    @Override
+    void set(Provider<Map<K, V>> provider) {
+        // TODO
+    }
+
+    @Override
+    void unset() {
+        this.m.clear()
+    }
+
+    @Override
+    Map<K, V> getConvention() {
+        this.convention
+    }
+
+    @Override
+    void setConvention(Map<K, V> kvMap) {
+        this.convention.clear()
+        this.convention.putAll(kvMap)
+    }
+
+    @Override
+    void setConvention(Provider<Map<K, V>> provider) {
+        // TODO
+    }
+
+    @Override
+    void unsetConvention() {
+        this.convention.clear()
+    }
+
+    @Override
+    void map(UnaryOperator<Map<K, V>> operator) {
+        this.m.putAll(operator.apply(this.convention + this.m))
+    }
+
+    @Override
+    void flatMap(Function<Map<K, V>, Provider<Map<K, V>>> function) {
+        // TODO
+    }
+
+    @Override
+    Map<K, V> provide() {
+        this.convention + this.m
+    }
+
+    @Override
+    CollectionProvider<Map<K, V>> plus(Provider<Map<K, V>> other) {
+        // TODO
+    }
+
+    @Override
+    CollectionProvider<Map<K, V>> asType(Class<CollectionProvider> collectionProviderClass) {
+        // TODO
+    }
+
+    @Override
+    boolean isEmpty() {
+        return false
+    }
+
+}
diff --git a/api/src/main/groovy/com/jessebrault/ssg/provider/Provider.groovy b/api/src/main/groovy/com/jessebrault/ssg/provider/Provider.groovy
index 2473250..75212e9 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/provider/Provider.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/provider/Provider.groovy
@@ -7,6 +7,7 @@ interface Provider<T> {
     @Deprecated
     CollectionProvider<T> plus(Provider<T> other)
 
+    @Deprecated
     CollectionProvider<T> asType(Class<CollectionProvider> collectionProviderClass)
 
     boolean isEmpty()
diff --git a/sketchingBaseBuild.groovy b/sketchingBaseBuild.groovy
new file mode 100644
index 0000000..ec0ea15
--- /dev/null
+++ b/sketchingBaseBuild.groovy
@@ -0,0 +1,36 @@
+abstractBuild(name: 'redDogAll', extends: 'default') {
+    siteSpec.merge {
+        name = 'Red Dog Ensemble'
+        baseUrl = 'https://reddogensemble.com'
+    }
+
+    globals.merge {
+        greeting = 'Say hello to good music!'
+    }
+
+    sources { types ->
+        models.map { acc ->
+            old + someMethodThatGetsEventModels()
+        }
+    }
+
+    taskFactories { sources ->
+        register(name: 'eventToHtml', supplier: ModelToHtmlFactory::new) {
+            modelsProvider.map { acc ->
+                acc + CollectionProviders.fromSupplier {
+                    sources.models.provide().findAll { it.name.startsWith('event/') }
+                }
+            }
+        }
+    }
+}
+
+build(name: 'preview', extends: 'redDogAll') {
+    siteSpec.merge {
+        baseUrl += '/preview' // if possible
+    }
+
+    globals.merge {
+        greeting = 'Hello from preview!'
+    }
+}
\ No newline at end of file