diff --git a/libropkg/include/ropkg/pkg-expr.h b/libropkg/include/ropkg/pkg-expr.h
new file mode 100644
index 0000000..5c3d391
--- /dev/null
+++ b/libropkg/include/ropkg/pkg-expr.h
@@ -0,0 +1,51 @@
+#ifndef ROPKG_PKG_EXPR_H_
+#define ROPKG_PKG_EXPR_H_
+
+#include <ropkg/misc.h>
+#include <ropkg/status.h>
+
+enum ropkg_pkg_expr_type {
+	ROPKG_PKG_EXPR_NODE_PKG,
+	ROPKG_PKG_EXPR_NODE_AND,
+	ROPKG_PKG_EXPR_NODE_OR,
+	ROPKG_PKG_EXPR_NODE_GROUP,
+};
+
+enum ropkg_comparison_op;
+
+struct ropkg_version;
+
+struct ropkg_pkg_expr;
+struct ropkg_pkg_expr_pkg;
+struct ropkg_pkg_expr_and;
+struct ropkg_pkg_expr_or;
+
+ROPKG_API void ropkg_pkg_expr_destroy(struct ropkg_pkg_expr *expr);
+
+ROPKG_API b_result
+ropkg_pkg_expr_parse(const char *s, struct ropkg_pkg_expr **out);
+
+ROPKG_API enum ropkg_pkg_expr_type ropkg_pkg_expr_get_type(
+	const struct ropkg_pkg_expr *expr);
+
+ROPKG_API struct ropkg_pkg_expr_pkg *ropkg_pkg_expr_pkg_create(void);
+ROPKG_API const char *ropkg_pkg_expr_pkg_get_name(
+	const struct ropkg_pkg_expr_pkg *expr);
+ROPKG_API enum ropkg_comparison_op ropkg_pkg_expr_pkg_get_version_predicate(
+	const struct ropkg_pkg_expr_pkg *expr);
+ROPKG_API const struct ropkg_version *ropkg_pkg_expr_pkg_get_version(
+	const struct ropkg_pkg_expr_pkg *expr);
+
+ROPKG_API struct ropkg_pkg_expr_and *ropkg_pkg_expr_and_create(void);
+ROPKG_API const struct ropkg_pkg_expr *ropkg_pkg_expr_and_get_left_node(
+	const struct ropkg_pkg_expr_and *expr);
+ROPKG_API const struct ropkg_pkg_expr *ropkg_pkg_expr_and_get_right_node(
+	const struct ropkg_pkg_expr_and *expr);
+
+ROPKG_API struct ropkg_pkg_expr_or *ropkg_pkg_expr_or_create(void);
+ROPKG_API const struct ropkg_pkg_expr *ropkg_pkg_expr_or_get_left_node(
+	const struct ropkg_pkg_expr_or *expr);
+ROPKG_API const struct ropkg_pkg_expr *ropkg_pkg_expr_or_get_right_node(
+	const struct ropkg_pkg_expr_or *expr);
+
+#endif
diff --git a/libropkg/pkg-expr.c b/libropkg/pkg-expr.c
new file mode 100644
index 0000000..ec1cd95
--- /dev/null
+++ b/libropkg/pkg-expr.c
@@ -0,0 +1,639 @@
+#include "pkg-expr.h"
+
+#include <blue/core/error.h>
+#include <blue/object/string.h>
+#include <ctype.h>
+#include <stdlib.h>
+#include <string.h>
+
+enum parse_state {
+	PARSE_NONE = 0,
+	PARSE_PKG_NAME,
+	PARSE_PKG_MID,
+	PARSE_PKG_VERSION,
+	PARSE_PKG_VERSION_PREDICATE,
+	PARSE_PKG_VERSION_MID,
+	PARSE_PKG_VERSION_ID,
+	PARSE_PKG_END,
+
+	PARSE_AND_SEP,
+	PARSE_OR_SEP,
+};
+
+struct parse_ctx {
+	const char *ctx_str;
+	b_string *ctx_temp;
+	enum parse_state ctx_state;
+	size_t ctx_i;
+	b_queue ctx_stack, ctx_queue;
+};
+
+static struct ropkg_pkg_expr *parse_ctx_peek_stack(struct parse_ctx *ctx)
+{
+	b_queue_entry *entry = b_queue_last(&ctx->ctx_stack);
+	if (!entry) {
+		return NULL;
+	}
+
+	return b_unbox(struct ropkg_pkg_expr, entry, expr_entry);
+}
+
+static struct ropkg_pkg_expr *parse_ctx_pop(struct parse_ctx *ctx)
+{
+	b_queue_entry *entry = b_queue_pop_back(&ctx->ctx_stack);
+	if (!entry) {
+		return NULL;
+	}
+
+	return b_unbox(struct ropkg_pkg_expr, entry, expr_entry);
+}
+
+static void parse_ctx_push(struct parse_ctx *ctx, struct ropkg_pkg_expr *expr)
+{
+	b_queue_push_back(&ctx->ctx_stack, &expr->expr_entry);
+}
+
+static struct ropkg_pkg_expr *parse_ctx_dequeue(struct parse_ctx *ctx)
+{
+	b_queue_entry *entry = b_queue_pop_front(&ctx->ctx_queue);
+	if (!entry) {
+		return NULL;
+	}
+
+	return b_unbox(struct ropkg_pkg_expr, entry, expr_entry);
+}
+
+static void parse_ctx_enqueue(
+	struct parse_ctx *ctx,
+	struct ropkg_pkg_expr *expr)
+{
+	b_queue_push_back(&ctx->ctx_queue, &expr->expr_entry);
+}
+
+static char parse_ctx_peek(struct parse_ctx *ctx)
+{
+	return ctx->ctx_str[ctx->ctx_i];
+}
+
+static char parse_ctx_advance(struct parse_ctx *ctx)
+{
+	if (!ctx->ctx_str[ctx->ctx_i]) {
+		return 0;
+	}
+
+	ctx->ctx_i++;
+
+	while (1) {
+		char c = parse_ctx_peek(ctx);
+		if (isspace(c)) {
+			ctx->ctx_i++;
+			continue;
+		}
+
+		break;
+	}
+
+	return ctx->ctx_str[ctx->ctx_i];
+}
+
+static void parse_ctx_cleanup(struct parse_ctx *ctx)
+{
+	if (ctx->ctx_temp) {
+		b_string_release(ctx->ctx_temp);
+	}
+
+	struct ropkg_pkg_expr *expr = parse_ctx_dequeue(ctx);
+	while (expr) {
+		ropkg_pkg_expr_destroy(expr);
+		expr = parse_ctx_dequeue(ctx);
+	}
+
+	expr = parse_ctx_pop(ctx);
+	while (expr) {
+		ropkg_pkg_expr_destroy(expr);
+		expr = parse_ctx_pop(ctx);
+	}
+}
+
+enum ropkg_status ropkg_pkg_expr_create(struct ropkg_pkg_expr **out)
+{
+	return ROPKG_SUCCESS;
+}
+
+void ropkg_pkg_expr_destroy(struct ropkg_pkg_expr *expr)
+{
+	b_queue q = B_QUEUE_INIT;
+	b_queue_push_back(&q, &expr->expr_entry);
+
+	while (1) {
+		b_queue_entry *entry = b_queue_pop_front(&q);
+		if (!entry) {
+			break;
+		}
+
+		expr = b_unbox(struct ropkg_pkg_expr, entry, expr_entry);
+
+		switch (expr->expr_type) {
+		case ROPKG_PKG_EXPR_NODE_PKG: {
+			struct ropkg_pkg_expr_pkg *pkg_node
+				= (struct ropkg_pkg_expr_pkg *)expr;
+			if (pkg_node->pkg_name) {
+				free(pkg_node->pkg_name);
+			}
+
+			if (pkg_node->pkg_version) {
+				ropkg_version_destroy(pkg_node->pkg_version);
+			}
+
+			break;
+		case ROPKG_PKG_EXPR_NODE_AND: {
+			struct ropkg_pkg_expr_and *and_node
+				= (struct ropkg_pkg_expr_and *)expr;
+			if (and_node->and_left) {
+				b_queue_push_back(
+					&q,
+					&and_node->and_left->expr_entry);
+			}
+
+			if (and_node->and_right) {
+				b_queue_push_back(
+					&q,
+					&and_node->and_right->expr_entry);
+			}
+			break;
+		}
+		case ROPKG_PKG_EXPR_NODE_OR: {
+			struct ropkg_pkg_expr_or *or_node
+				= (struct ropkg_pkg_expr_or *)expr;
+			if (or_node->or_left) {
+				b_queue_push_back(
+					&q,
+					&or_node->or_left->expr_entry);
+			}
+
+			if (or_node->or_right) {
+				b_queue_push_back(
+					&q,
+					&or_node->or_right->expr_entry);
+			}
+			break;
+		}
+		default:
+			break;
+		}
+		}
+
+		free(expr);
+	}
+}
+
+static b_result parse_pkg_name(
+	struct parse_ctx *ctx,
+	struct ropkg_pkg_expr_pkg *pkg)
+{
+	b_string_clear(ctx->ctx_temp);
+
+	while (1) {
+		char c = parse_ctx_peek(ctx);
+		if (!isalnum(c) && c != '+' && c != '-' && c != '_') {
+			break;
+		}
+
+		char s[] = {c, 0};
+		b_string_append_cstr(ctx->ctx_temp, s);
+		parse_ctx_advance(ctx);
+	}
+
+	pkg->pkg_name = b_string_steal(ctx->ctx_temp);
+	return B_RESULT_SUCCESS;
+}
+
+static b_result parse_pkg_version_predicate(
+	struct parse_ctx *ctx,
+	struct ropkg_pkg_expr_pkg *pkg)
+{
+	b_string_clear(ctx->ctx_temp);
+
+	while (1) {
+		char c = parse_ctx_peek(ctx);
+		if (!ispunct(c)) {
+			break;
+		}
+
+		char s[] = {c, 0};
+		b_string_append_cstr(ctx->ctx_temp, s);
+		parse_ctx_advance(ctx);
+	}
+
+	const char *pred = b_string_ptr(ctx->ctx_temp);
+	if (!strcmp(pred, ">=")) {
+		pkg->pkg_version_predicate = ROPKG_OP_GREATER_EQUAL;
+	} else if (!strcmp(pred, ">")) {
+		pkg->pkg_version_predicate = ROPKG_OP_GREATER_THAN;
+	} else if (!strcmp(pred, "<=")) {
+		pkg->pkg_version_predicate = ROPKG_OP_LESS_EQUAL;
+	} else if (!strcmp(pred, "<")) {
+		pkg->pkg_version_predicate = ROPKG_OP_LESS_THAN;
+	} else if (!strcmp(pred, "==") || !strcmp(pred, "=")) {
+		pkg->pkg_version_predicate = ROPKG_OP_EQUAL;
+	} else {
+		return b_error_with_code(
+			ROPKG_ERROR_VENDOR,
+			ROPKG_ERR_INVALID_PKG_EXPR);
+	}
+
+	return B_RESULT_SUCCESS;
+}
+
+static b_result parse_pkg_version_id(
+	struct parse_ctx *ctx,
+	struct ropkg_pkg_expr_pkg *pkg)
+{
+	b_string_clear(ctx->ctx_temp);
+	while (1) {
+		char c = parse_ctx_peek(ctx);
+		if (!isalnum(c) && c != '.' && c != '-' && c != '~') {
+			break;
+		}
+
+		char s[] = {c, 0};
+		b_string_append_cstr(ctx->ctx_temp, s);
+		parse_ctx_advance(ctx);
+	}
+
+	struct ropkg_version *version = NULL;
+	enum ropkg_status status = ropkg_version_create(&version);
+	if (status != ROPKG_SUCCESS) {
+		return b_error_with_code(ROPKG_ERROR_VENDOR, status);
+	}
+
+	b_result result
+		= ropkg_version_parse(version, b_string_ptr(ctx->ctx_temp));
+	if (b_result_is_error(result)) {
+		ropkg_version_destroy(version);
+		version = NULL;
+	}
+
+	pkg->pkg_version = version;
+	return b_result_propagate(result);
+}
+
+static b_result parse_pkg_version(
+	struct parse_ctx *ctx,
+	struct ropkg_pkg_expr_pkg *pkg)
+{
+	parse_ctx_advance(ctx);
+
+	b_result result = B_RESULT_SUCCESS;
+	char c = parse_ctx_peek(ctx);
+	if (c == '>' || c == '<' || c == '=') {
+		result = parse_pkg_version_predicate(ctx, pkg);
+	}
+
+	if (b_result_is_error(result)) {
+		return result;
+	}
+
+	c = parse_ctx_peek(ctx);
+
+	if (isalnum(c)) {
+		result = parse_pkg_version_id(ctx, pkg);
+	} else {
+		result = b_error_with_code(
+			ROPKG_ERROR_VENDOR,
+			ROPKG_ERR_INVALID_PKG_EXPR);
+	}
+
+	c = parse_ctx_peek(ctx);
+	if (c == ')') {
+		parse_ctx_advance(ctx);
+	} else {
+		result = b_error_with_code(
+			ROPKG_ERROR_VENDOR,
+			ROPKG_ERR_INVALID_PKG_EXPR);
+	}
+
+	return result;
+}
+
+static b_result parse_pkg(struct parse_ctx *ctx)
+{
+	struct ropkg_pkg_expr_pkg *pkg = ropkg_pkg_expr_pkg_create();
+
+	b_result result = B_RESULT_SUCCESS;
+	char c = parse_ctx_peek(ctx);
+	if (isalpha(c)) {
+		result = parse_pkg_name(ctx, pkg);
+	}
+
+	if (b_result_is_error(result)) {
+		ropkg_pkg_expr_destroy((struct ropkg_pkg_expr *)pkg);
+		return b_result_propagate(result);
+	}
+
+	c = parse_ctx_peek(ctx);
+	if (c == '(') {
+		result = parse_pkg_version(ctx, pkg);
+	}
+
+	if (b_result_is_error(result)) {
+		ropkg_pkg_expr_destroy((struct ropkg_pkg_expr *)pkg);
+		return b_result_propagate(result);
+	}
+
+	parse_ctx_enqueue(ctx, &pkg->pkg_base);
+
+	return result;
+}
+
+static b_result parse_and(struct parse_ctx *ctx)
+{
+	parse_ctx_advance(ctx);
+
+	struct ropkg_pkg_expr_and *and_node = ropkg_pkg_expr_and_create();
+
+	while (1) {
+		struct ropkg_pkg_expr *top = parse_ctx_peek_stack(ctx);
+		if (!top) {
+			break;
+		}
+
+		if (top->expr_type == ROPKG_PKG_EXPR_NODE_GROUP) {
+			break;
+		}
+
+		if (top->expr_type < and_node->and_base.expr_type) {
+			break;
+		}
+
+		top = parse_ctx_pop(ctx);
+		parse_ctx_enqueue(ctx, top);
+	}
+
+	parse_ctx_push(ctx, &and_node->and_base);
+	return B_RESULT_SUCCESS;
+}
+
+static b_result parse_or(struct parse_ctx *ctx)
+{
+	parse_ctx_advance(ctx);
+
+	struct ropkg_pkg_expr_or *or_node = ropkg_pkg_expr_or_create();
+
+	while (1) {
+		struct ropkg_pkg_expr *top = parse_ctx_peek_stack(ctx);
+		if (!top) {
+			break;
+		}
+
+		if (top->expr_type < or_node->or_base.expr_type) {
+			break;
+		}
+
+		top = parse_ctx_pop(ctx);
+		parse_ctx_enqueue(ctx, top);
+	}
+
+	parse_ctx_push(ctx, &or_node->or_base);
+	return B_RESULT_SUCCESS;
+}
+
+static b_result parse_group_start(struct parse_ctx *ctx)
+{
+	parse_ctx_advance(ctx);
+
+	struct ropkg_pkg_expr *group_node = malloc(sizeof *group_node);
+	if (!group_node) {
+		return b_error_with_code(
+			ROPKG_ERROR_VENDOR,
+			ROPKG_ERR_NO_MEMORY);
+	}
+
+	memset(group_node, 0x0, sizeof *group_node);
+
+	group_node->expr_type = ROPKG_PKG_EXPR_NODE_GROUP;
+
+	parse_ctx_push(ctx, group_node);
+	return B_RESULT_SUCCESS;
+}
+
+static b_result parse_group_end(struct parse_ctx *ctx)
+{
+	parse_ctx_advance(ctx);
+
+	bool done = false;
+
+	while (!done) {
+		struct ropkg_pkg_expr *expr = parse_ctx_pop(ctx);
+
+		if (!expr) {
+			return b_error_with_code(
+				ROPKG_ERROR_VENDOR,
+				ROPKG_ERR_INVALID_PKG_EXPR);
+		}
+
+		switch (expr->expr_type) {
+		case ROPKG_PKG_EXPR_NODE_GROUP:
+			free(expr);
+			done = true;
+			break;
+		default:
+			parse_ctx_enqueue(ctx, expr);
+			break;
+		}
+	}
+
+	return B_RESULT_SUCCESS;
+}
+
+b_result ropkg_pkg_expr_parse(const char *s, struct ropkg_pkg_expr **out)
+{
+	while (isspace(*s)) {
+		s++;
+	}
+
+	struct parse_ctx ctx = {
+		.ctx_str = s,
+		.ctx_temp = b_string_create(),
+	};
+
+	b_result result = B_RESULT_SUCCESS;
+
+	while (!b_result_is_error(result)) {
+		char c = parse_ctx_peek(&ctx);
+		if (c == 0) {
+			break;
+		}
+
+		if (c == '(') {
+			result = parse_group_start(&ctx);
+		} else if (c == ')') {
+			result = parse_group_end(&ctx);
+		} else if (c == ',') {
+			result = parse_and(&ctx);
+		} else if (c == '|') {
+			result = parse_or(&ctx);
+		} else if (isalpha(c)) {
+			result = parse_pkg(&ctx);
+		} else {
+			result = b_error_with_code(
+				ROPKG_ERROR_VENDOR,
+				ROPKG_ERR_INVALID_PKG_EXPR);
+			break;
+		}
+	}
+
+	if (b_result_is_error(result)) {
+		parse_ctx_cleanup(&ctx);
+		return result;
+	}
+
+	struct ropkg_pkg_expr *expr = parse_ctx_pop(&ctx);
+	while (expr) {
+		parse_ctx_enqueue(&ctx, expr);
+		expr = parse_ctx_pop(&ctx);
+	}
+
+	while (1) {
+		expr = parse_ctx_dequeue(&ctx);
+		if (!expr) {
+			break;
+		}
+
+		if (expr->expr_type == ROPKG_PKG_EXPR_NODE_PKG) {
+			parse_ctx_push(&ctx, expr);
+			continue;
+		}
+
+		if (expr->expr_type == ROPKG_PKG_EXPR_NODE_GROUP) {
+			parse_ctx_cleanup(&ctx);
+			return b_error_with_code(
+				ROPKG_ERROR_VENDOR,
+				ROPKG_ERR_INVALID_PKG_EXPR);
+		}
+
+		struct ropkg_pkg_expr *left = NULL, *right = NULL;
+		right = parse_ctx_pop(&ctx);
+		left = parse_ctx_pop(&ctx);
+		if (!left || !right) {
+			parse_ctx_cleanup(&ctx);
+			return b_error_with_code(
+				ROPKG_ERROR_VENDOR,
+				ROPKG_ERR_INVALID_PKG_EXPR);
+		}
+
+		switch (expr->expr_type) {
+		case ROPKG_PKG_EXPR_NODE_AND: {
+			struct ropkg_pkg_expr_and *and_node
+				= (struct ropkg_pkg_expr_and *)expr;
+			and_node->and_left = left;
+			and_node->and_right = right;
+			break;
+		}
+		case ROPKG_PKG_EXPR_NODE_OR: {
+			struct ropkg_pkg_expr_or *or_node
+				= (struct ropkg_pkg_expr_or *)expr;
+			or_node->or_left = left;
+			or_node->or_right = right;
+			break;
+		}
+		default:
+			break;
+		}
+
+		parse_ctx_push(&ctx, expr);
+	}
+
+	*out = parse_ctx_pop(&ctx);
+	parse_ctx_cleanup(&ctx);
+	return result;
+}
+
+enum ropkg_pkg_expr_type ropkg_pkg_expr_get_type(
+	const struct ropkg_pkg_expr *expr)
+{
+	return expr->expr_type;
+}
+
+struct ropkg_pkg_expr_pkg *ropkg_pkg_expr_pkg_create(void)
+{
+	struct ropkg_pkg_expr_pkg *out = malloc(sizeof *out);
+	if (!out) {
+		return NULL;
+	}
+
+	memset(out, 0x0, sizeof *out);
+
+	out->pkg_base.expr_type = ROPKG_PKG_EXPR_NODE_PKG;
+
+	return out;
+}
+
+const char *ropkg_pkg_expr_pkg_get_name(const struct ropkg_pkg_expr_pkg *expr)
+{
+	return expr->pkg_name;
+}
+
+enum ropkg_comparison_op ropkg_pkg_expr_pkg_get_version_predicate(
+	const struct ropkg_pkg_expr_pkg *expr)
+{
+	return expr->pkg_version_predicate;
+}
+
+const struct ropkg_version *ropkg_pkg_expr_pkg_get_version(
+	const struct ropkg_pkg_expr_pkg *expr)
+{
+	return expr->pkg_version;
+}
+
+struct ropkg_pkg_expr_and *ropkg_pkg_expr_and_create(void)
+{
+	struct ropkg_pkg_expr_and *out = malloc(sizeof *out);
+	if (!out) {
+		return NULL;
+	}
+
+	memset(out, 0x0, sizeof *out);
+
+	out->and_base.expr_type = ROPKG_PKG_EXPR_NODE_AND;
+
+	return out;
+}
+
+const struct ropkg_pkg_expr *ropkg_pkg_expr_and_get_left_node(
+	const struct ropkg_pkg_expr_and *expr)
+{
+	return expr->and_left;
+}
+
+const struct ropkg_pkg_expr *ropkg_pkg_expr_and_get_right_node(
+	const struct ropkg_pkg_expr_and *expr)
+{
+	return expr->and_right;
+}
+
+struct ropkg_pkg_expr_or *ropkg_pkg_expr_or_create(void)
+{
+	struct ropkg_pkg_expr_or *out = malloc(sizeof *out);
+	if (!out) {
+		return NULL;
+	}
+
+	memset(out, 0x0, sizeof *out);
+
+	out->or_base.expr_type = ROPKG_PKG_EXPR_NODE_OR;
+
+	return out;
+}
+
+const struct ropkg_pkg_expr *ropkg_pkg_expr_or_get_left_node(
+	const struct ropkg_pkg_expr_or *expr)
+{
+	return expr->or_left;
+}
+
+const struct ropkg_pkg_expr *ropkg_pkg_expr_or_get_right_node(
+	const struct ropkg_pkg_expr_or *expr)
+{
+	return expr->or_right;
+}
diff --git a/libropkg/pkg-expr.h b/libropkg/pkg-expr.h
new file mode 100644
index 0000000..dd206b8
--- /dev/null
+++ b/libropkg/pkg-expr.h
@@ -0,0 +1,29 @@
+#ifndef _PKG_EXPR_H_
+#define _PKG_EXPR_H_
+
+#include <ropkg/pkg-expr.h>
+#include <ropkg/version.h>
+
+struct ropkg_pkg_expr {
+	enum ropkg_pkg_expr_type expr_type;
+	b_queue_entry expr_entry;
+};
+
+struct ropkg_pkg_expr_pkg {
+	struct ropkg_pkg_expr pkg_base;
+	char *pkg_name;
+	enum ropkg_comparison_op pkg_version_predicate;
+	struct ropkg_version *pkg_version;
+};
+
+struct ropkg_pkg_expr_and {
+	struct ropkg_pkg_expr and_base;
+	struct ropkg_pkg_expr *and_left, *and_right;
+};
+
+struct ropkg_pkg_expr_or {
+	struct ropkg_pkg_expr or_base;
+	struct ropkg_pkg_expr *or_left, *or_right;
+};
+
+#endif