Dear TOSCA Experts, the following question is related to a problem under discussion in the ETSI NFV SOL001 group. In the below second service template (example-top.tosca.yaml), can the value of property_2 come from a substitution template? In other words, is the second service template valid? example-type.tosca.yaml: tosca_definitions_version: tosca_simple_yaml_1_2 node_types: node_type_1: derived_from: tosca.nodes.Root properties: property_1: type: string constraints: - valid_values: [ value_1, value_2 ] property_2: type: string example-top.tosca.yaml: tosca_definitions_version: tosca_simple_yaml_1_2 imports: - example-type.tosca.yaml topology_template: node_templates: node_template_1: type: node_type_1 properties: property_1: value_1 # property value constraint for matching outputs: output_1: value: { get_property: [ node_template_1, property_2 ] } # value_3 from the sole matching substitution example-subst-1.tosca.yaml: tosca_definitions_version: tosca_simple_yaml_1_2 imports: - example-type.tosca.yaml topology_template: substitution_mappings: node_type: node_type_1 properties: property_1: value_1 property_2: value_3 example-subst-2.tosca.yaml: tosca_definitions_version: tosca_simple_yaml_1_2 imports: - example-type.tosca.yaml topology_template: substitution_mappings: node_type: node_type_1 properties: property_1: value_2 property_2: value_4 In case the second service template is invalid, we need to use a work-around which is not perfect, e.g.: example-type.tosca.yaml (modified): tosca_definitions_version: tosca_simple_yaml_1_2 node_types: node_type_1: derived_from: tosca.nodes.Root properties: property_1: type: string constraints: - valid_values: [ value_1, value_2 ] property_2: type: string default: '' Looking forward to receiving your response, kind regards, Gábor