diff --git a/gdtf-spec.md b/gdtf-spec.md
index 1172413..9c8f799 100644
--- a/gdtf-spec.md
+++ b/gdtf-spec.md
@@ -173,11 +173,18 @@ all firmware revisions of the device.
 
 ```
 
-The ZIP archive name is specified as follows:
+The ZIP archive name is recommended to be specified as follows:
+
 `<ManufacturerName>@<FixtureTypeName>@<OptionalComment>`
 
 Example: `generic@led@comment`
 
+It is recommended to limit the filename to the POSIX "Fully Portable Filenames"
+character set: [A-Z], [a-z], [0-9], the symbols '_' (U+005F), '-' (U+002D) and
+a maximum of one '.' (U+002E), if needed, use '_' (U+005F) or '-' (U+002D) to
+replace unsupported characters.
+
+
 UTF-8 has to be used to encode the XML file. Each XML file internally
 consists of XML nodes. Each XML node could have XML attributes and XML
 children. Each XML attribute has a value. If a XML attribute is not
@@ -256,9 +263,9 @@ attributes of the fixture type are specified in [table 3](#user-content-table-3
 
 | XML Attribute Name | Value Type | Description  |
 |----|----|----|
-| Name               | [Name](#user-content-attrtype-name )         | Name of the fixture type. As it is based on Name, it is safe for parsing. |
-| ShortName          | [String](#user-content-attrtype-string )     | Shortened name of the fixture type. Non detailed version or an abbreviation. Can use any characters or symbols. |
-| LongName           | [String](#user-content-attrtype-string )     | Detailed, complete name of the fixture type, can include any characters or extra symbols. |
+| Name               | [Name](#user-content-attrtype-name )         | Name of the fixture type.|
+| ShortName          | [String](#user-content-attrtype-string )     | Shortened name of the fixture type. Non detailed version or an abbreviation. Can use any characters or symbols. Used in user interfaces in places where there is not enough space.|
+| LongName           | [String](#user-content-attrtype-string )     | Detailed, complete name of the fixture type, can include any characters or extra symbols.|
 | Manufacturer       | [String](#user-content-attrtype-string )     | Manufacturer of the fixture type.|
 | Description        | [String](#user-content-attrtype-string )     | Description of the fixture type. |
 | FixtureTypeID      | [GUID](#user-content-attrtype-guid )         | Unique number of the fixture type. |