The heat_template_version field indicates the template version. Each HOT template includes the heat_template_version field that specifies the template version. Different HOT template versions support different internal functions. RTS supports the following HOT template versions:

heat_template_version 2013-05-23:
The heat_template_version 2013-05-23 template supports the following internal functions:

get_attr, get_file, get_param, get_resource, list_join, resource_facade, str_replace, Fn::Base64, Fn::GetAZs, Fn::Join, Fn::MemberListToMap, Fn::Replace, Fn::ResourceFacade, Fn::Select, Fn::Split, and Ref

heat_template_version 2014-10-16:
The heat_template_version 2014-10-16 template supports the following internal functions:

get_attr, get_file, get_param, get_resource, list_join, resource_facade, str_replace, and Fn::Select
heat_template_version 2015-04-30:
The heat_template_version 2015-04-30 template supports the following internal functions:

get_attr, get_file, get_param, get_resource, list_join, repeat, digest, resource_facade, str_replace, and Fn::Select
heat_template_version 2015-10-15:
The heat_template_version 2015-10-15 template supports the following internal functions:

get_attr, get_file, get_param, get_resource, list_join, repeat, digest, resource_facade, str_replace, and str_split
heat_template_version 2016-04-08:
The heat_template_version 2016-04-08 template supports the following internal functions:

digest, get_attr, get_file, get_param, get_resource, list_join, map_merge, repeat, resource_facade, str_replace, and str_split

Template Version