diff --git a/business_logic.py b/business_logic.py
new file mode 100644
index 0000000..ccc64e6
--- /dev/null
+++ b/business_logic.py
@@ -0,0 +1,240 @@
+from datetime import date, datetime
+from typing import Dict, Any, List, Optional, Tuple
+from data_access import StudentDataAccess
+
+
+class IDCardValidator:
+    """身份证验证工具类"""
+
+    @staticmethod
+    def validate_id_card(id_card: str) -> Tuple[bool, str]:
+        """验证身份证号有效性"""
+        # 基本格式验证
+        if len(id_card) != 18:
+            return False, "身份证号必须为18位"
+
+        # 前17位必须是数字，最后一位可以是数字或X
+        if not (id_card[:-1].isdigit() and (id_card[-1].isdigit() or id_card[-1].upper() == 'X')):
+            return False, "身份证号格式不正确，前17位必须是数字，最后一位可以是数字或X"
+
+        # 验证出生日期
+        birth_date = id_card[6:14]
+        if not IDCardValidator.validate_birth_date(birth_date):
+            return False, "身份证号中的出生日期无效"
+
+        # 验证校验码
+        if not IDCardValidator.validate_check_code(id_card):
+            return False, "身份证号校验码不正确"
+
+        return True, "身份证号有效"
+
+    @staticmethod
+    def validate_birth_date(birth_date: str) -> bool:
+        """验证出生日期是否有效"""
+        try:
+            # 尝试解析日期
+            year = int(birth_date[0:4])
+            month = int(birth_date[4:6])
+            day = int(birth_date[6:8])
+
+            # 检查日期范围
+            if not (1900 <= year <= date.today().year):
+                return False
+            if not (1 <= month <= 12):
+                return False
+
+            # 检查每月天数
+            max_day = IDCardValidator.get_days_in_month(year, month)
+            if not (1 <= day <= max_day):
+                return False
+
+            return True
+        except:
+            return False
+
+    @staticmethod
+    def get_days_in_month(year: int, month: int) -> int:
+        """获取某年某月的天数"""
+        if month == 2:
+            return 29 if IDCardValidator.is_leap_year(year) else 28
+        elif month in [4, 6, 9, 11]:
+            return 30
+        else:
+            return 31
+
+    @staticmethod
+    def is_leap_year(year: int) -> bool:
+        """判断是否为闰年"""
+        return (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)
+
+    @staticmethod
+    def validate_check_code(id_card: str) -> bool:
+        """验证身份证校验码"""
+        # 权重因子
+        weight = [7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2]
+        # 校验码对应表
+        check_code_map = ['1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2']
+
+        # 计算加权和
+        total = sum(int(id_card[i]) * weight[i] for i in range(17))
+        # 计算校验码
+        calculated_code = check_code_map[total % 11]
+
+        # 比较校验码
+        return id_card[-1].upper() == calculated_code
+
+    @staticmethod
+    def get_gender(id_card: str) -> str:
+        """根据身份证号获取性别"""
+        if len(id_card) < 17:
+            return "未知"
+        gender_num = int(id_card[16])
+        return "男" if gender_num % 2 == 1 else "女"
+
+    @staticmethod
+    def get_birth_date(id_card: str) -> Optional[date]:
+        """从身份证号获取出生日期"""
+        if len(id_card) < 14:
+            return None
+        try:
+            birth_str = id_card[6:14]
+            return datetime.strptime(birth_str, "%Y%m%d").date()
+        except:
+            return None
+
+    @staticmethod
+    def calculate_age(id_card: str) -> Optional[int]:
+        """根据身份证号计算年龄"""
+        birth_date = IDCardValidator.get_birth_date(id_card)
+        if not birth_date:
+            return None
+
+        today = date.today()
+        age = today.year - birth_date.year
+        # 如果生日还没到，年龄减1
+        if (today.month, today.day) < (birth_date.month, birth_date.day):
+            age -= 1
+        return age
+
+
+class StudentService:
+    def __init__(self, data_access: StudentDataAccess):
+        self.data_access = data_access
+        self.subject_name = {
+            'math': '数学',
+            'python': 'Python程序设计',
+            'english': '英语',
+            'physics': '物理',
+            'sum': '总分'
+        }
+
+    def validate_id_card(self, id_card: str) -> Tuple[bool, str]:
+        """验证身份证号格式"""
+        return IDCardValidator.validate_id_card(id_card)
+
+    def is_id_card_exists(self, id_card: str, exclude_id: str = None) -> bool:
+        """检查身份证号是否已存在"""
+        students = self.data_access.get_all_students()
+        for sid, student in students.items():
+            if exclude_id and sid == exclude_id:
+                continue
+            if student['basic_info'].get('id_card', '').upper() == id_card.upper():
+                return True
+        return False
+
+    def add_student(self, student_info: Dict[str, Any]) -> bool:
+        """添加新学生"""
+        student_id = student_info['basic_info']['id']
+
+        # 验证学号
+        if not student_id.isdigit() or len(student_id) != 8:
+            raise ValueError("学号必须为8位数字！")
+
+        # 验证身份证号
+        id_card = student_info['basic_info'].get('id_card', '')
+        if not id_card:
+            raise ValueError("身份证号不能为空！")
+
+        is_valid, msg = self.validate_id_card(id_card)
+        if not is_valid:
+            raise ValueError(f"身份证号无效: {msg}")
+
+        if self.is_id_card_exists(id_card):
+            raise ValueError("该身份证号已存在！")
+
+        # 自动填充性别和出生日期
+        student_info['basic_info']['gender'] = IDCardValidator.get_gender(id_card)
+        birth_date = IDCardValidator.get_birth_date(id_card)
+        if birth_date:
+            student_info['basic_info']['birth_date'] = birth_date.strftime("%Y-%m-%d")
+            student_info['basic_info']['age'] = IDCardValidator.calculate_age(id_card)
+
+        # 计算总分
+        scores = student_info['score']
+        scores['sum'] = sum([scores['math'], scores['python'], scores['english'], scores['physics']])
+
+        return self.data_access.add_student(student_id, student_info)
+
+    def update_student(self, student_id: str, student_info: Dict[str, Any]) -> bool:
+        """更新学生信息"""
+        # 验证身份证号
+        id_card = student_info['basic_info'].get('id_card', '')
+        if id_card:  # 如果提供了身份证号才验证
+            is_valid, msg = self.validate_id_card(id_card)
+            if not is_valid:
+                raise ValueError(f"身份证号无效: {msg}")
+            if self.is_id_card_exists(id_card, exclude_id=student_id):
+                raise ValueError("该身份证号已被其他学生使用！")
+
+            # 自动更新性别和出生日期
+            student_info['basic_info']['gender'] = IDCardValidator.get_gender(id_card)
+            birth_date = IDCardValidator.get_birth_date(id_card)
+            if birth_date:
+                student_info['basic_info']['birth_date'] = birth_date.strftime("%Y-%m-%d")
+                student_info['basic_info']['age'] = IDCardValidator.calculate_age(id_card)
+
+        # 计算总分
+        scores = student_info['score']
+        scores['sum'] = sum([scores['math'], scores['python'], scores['english'], scores['physics']])
+
+        return self.data_access.update_student(student_id, student_info)
+
+    def delete_student(self, student_id: str) -> bool:
+        """删除学生"""
+        return self.data_access.delete_student(student_id)
+
+    def get_student(self, student_id: str) -> Dict[str, Any]:
+        """获取单个学生信息"""
+        return self.data_access.get_student(student_id)
+
+    def get_all_students(self) -> Dict[str, Any]:
+        """获取所有学生信息"""
+        return self.data_access.get_all_students()
+
+    def search_student_by_id(self, student_id: str) -> Dict[str, Any]:
+        """按学号查询学生信息"""
+        return self.data_access.get_student(student_id)
+
+    def get_statistics(self) -> Dict[str, float]:
+        """获取统计信息"""
+        students = self.data_access.get_all_students().values()
+        if not students:
+            return {}
+
+        total = len(students)
+        return {
+            'total': total,
+            'math_avg': sum(s['score']['math'] for s in students) / total,
+            'python_avg': sum(s['score']['python'] for s in students) / total,
+            'english_avg': sum(s['score']['english'] for s in students) / total,
+            'physics_avg': sum(s['score']['physics'] for s in students) / total,
+            'total_avg': sum(s['score']['sum'] for s in students) / total
+        }
+
+    def get_sorted_students(self) -> List[Dict[str, Any]]:
+        """按总分排序获取学生"""
+        students = list(self.data_access.get_all_students().values())
+        return sorted(students, key=lambda x: x['score']['sum'], reverse=True)
+
+    def load_data(self):
+        pass
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