diff -r 0cfbaf5c57a6 -r 576d4965434f src/CLIParser.h
--- a/src/CLIParser.h	Sat May 15 18:18:10 2021 +0200
+++ b/src/CLIParser.h	Sun May 16 17:33:35 2021 +0200
@@ -52,8 +52,19 @@
 		else throw relpipe::cli::RelpipeCLIException(L"Unable to parse entity value: " + value + L" (expecting „relation“, „attribute“ or „value“)", relpipe::cli::CLI::EXIT_CODE_BAD_CLI_ARGUMENTS);
 	}
 
+	ENTITY parseModifyTarget(const relpipe::common::type::StringX& value) {
+		if (value == L"relation-name") return ENTITY::RELATION;
+		else if (value == L"attribute-name") return ENTITY::ATTRIBUTE;
+		else if (value == L"value") return ENTITY::VALUE;
+		else throw relpipe::cli::RelpipeCLIException(L"Unable to parse entity value: " + value + L" (expecting „relation-name“, „attribute-name“ or „value“)", relpipe::cli::CLI::EXIT_CODE_BAD_CLI_ARGUMENTS);
+	}
+
 	void addRule(RelationConfiguration& currentRelation, RewriteRule& currentRule) {
-		if (currentRule.attribute.size()) {
+		if (currentRule.modify != ENTITY::DEFAULT) {
+			// the --value is optional → set defaults if missing:
+			if (currentRule.modify == ENTITY::RELATION && currentRule.value.size() == 0) currentRule.value = currentRelation.relation;
+			if (currentRule.modify == ENTITY::ATTRIBUTE && currentRule.value.size() == 0) currentRule.value = currentRule.attribute;
+
 			currentRule.attributePattern = currentRule.caseSensitive[ENTITY::ATTRIBUTE] ? std::wregex(currentRule.attribute) : std::wregex(currentRule.attribute, std::regex_constants::icase);
 			currentRule.valuePattern = currentRule.caseSensitive[ENTITY::VALUE] ? std::wregex(currentRule.value) : std::wregex(currentRule.value, std::regex_constants::icase);
 			currentRelation.rules.push_back(currentRule);
@@ -73,6 +84,7 @@
 public:
 
 	static const relpipe::common::type::StringX OPTION_RELATION;
+	static const relpipe::common::type::StringX OPTION_MODIFY;
 	static const relpipe::common::type::StringX OPTION_ATTRIBUTE;
 	static const relpipe::common::type::StringX OPTION_VALUE;
 	static const relpipe::common::type::StringX OPTION_REPLACEMENT;
@@ -90,8 +102,17 @@
 			if (option == OPTION_RELATION) {
 				addRelation(c, currentRelation, currentRule); // previous relation
 				currentRelation.relation = readNext(arguments, i);
+			} else if (option == OPTION_MODIFY) {
+				addRule(currentRelation, currentRule); // previous rule
+				currentRule.modify = parseModifyTarget(readNext(arguments, i));
+				if (currentRule.modify == ENTITY::VALUE) currentRule.modify = ENTITY::DEFAULT;
 			} else if (option == OPTION_ATTRIBUTE) {
-				addRule(currentRelation, currentRule); // previous rule
+				if (currentRule.modify == ENTITY::DEFAULT) {
+					currentRule.modify = ENTITY::VALUE;
+				} else if (currentRule.modify == ENTITY::VALUE) {
+					addRule(currentRelation, currentRule); // previous rule
+					currentRule.modify = ENTITY::VALUE;
+				}
 				currentRule.attribute = readNext(arguments, i);
 			} else if (option == OPTION_VALUE) {
 				currentRule.value = readNext(arguments, i);
@@ -100,13 +121,13 @@
 			} else if (option == OPTION_CASE_SENSITIVE) {
 				ENTITY entity = parseEntity(readNext(arguments, i));
 				bool value = parseBoolean(readNext(arguments, i));
-				if (currentRule.attribute.size()) currentRule.caseSensitive[entity] = value;
-				else currentRelation.caseSensitive[entity] = value;
+				if (currentRule.modify == ENTITY::DEFAULT) currentRelation.caseSensitive[entity] = value;
+				currentRule.caseSensitive[entity] = value;
 			} else if (option == OPTION_INVERT_MATCH) {
 				ENTITY entity = parseEntity(readNext(arguments, i));
 				bool value = parseBoolean(readNext(arguments, i));
-				if (currentRule.attribute.size()) currentRule.invertMatch[entity] = value;
-				else currentRelation.invertMatch[entity] = value;
+				if (currentRule.modify == ENTITY::DEFAULT) currentRelation.invertMatch[entity] = value;
+				currentRule.invertMatch[entity] = value;
 			} else throw relpipe::cli::RelpipeCLIException(L"Unsupported CLI option: " + option, relpipe::cli::CLI::EXIT_CODE_BAD_CLI_ARGUMENTS);
 		}
 		addRelation(c, currentRelation, currentRule); // last relation
@@ -119,6 +140,7 @@
 };
 
 const relpipe::common::type::StringX CLIParser::OPTION_RELATION = L"--relation";
+const relpipe::common::type::StringX CLIParser::OPTION_MODIFY = L"--modify";
 const relpipe::common::type::StringX CLIParser::OPTION_ATTRIBUTE = L"--attribute";
 const relpipe::common::type::StringX CLIParser::OPTION_VALUE = L"--value";
 const relpipe::common::type::StringX CLIParser::OPTION_REPLACEMENT = L"--replacement";