## What is the primary role of a **Boundary Object**? --- 🌐 It defines **interfaces** to and communicates with the **external environment**. %%% What does a **Boundary Class** typically represent in a UML class diagram? --- đŸ–Ĩī¸ It represents the **User Interface (UI)** or **external systems' interfaces**, depicting interactions between the system and its actors. %%% In terms of **External Interaction**, how does a Boundary Class function? --- 🔄 It acts as a **Proxy**: handling input/output operations and facilitating communication between the internal system and external entities. %%% What is the specific responsibility of a Boundary Object regarding **Hardware**? --- 🔌 **Device I/O**: It receives input from and/or sends output to a hardware device. %%% ## What are the **three key characteristics** of a Boundary Class? --- 1. **Interface Representation** (UI/External interfaces). 2. **External Interaction (Proxy)** (Mediating communication). 3. **Device I/O** (Hardware communication). %%% What is the primary function of an **Entity Object**? --- đŸ“Ļ It **encapsulates information** and represents data that needs to be stored and managed within the system. %%% What are the two types of **Entity Objects** based on data lifespan? --- âŗ 1. **Data abstraction objects**: Used for **transient** data (temporary). 2. **Database objects**: Used for **persistent** data (long-term). %%% In a UML class diagram, what do the **attributes** of an Entity Class represent? --- 📋 They represent the **properties or characteristics** of the entity, corresponding to specific data fields. %%% ## How do **Entity Classes** typically interact with one another? --- 🔗 Through **associations** (relationships) that indicate how different entities are connected. %%% If persistent data is stored in a database, what is the role of the **Entity Object**? --- 🎁 It acts as a **wrapper**: mapping database columns to the object's attributes. %%% Why is a **mutex** usually required when using Entity Objects in a multi-threaded environment? --- 🔒 Because Entity Objects are almost always **passive**, meaning they do not manage their own concurrency/execution flow. %%% What is the primary purpose of a **Control Object**? --- 🕹ī¸ It provides **overall coordination** for a collection of objects within the system. %%% How do Control Objects facilitate the fulfillment of a **Use Case**? --- đŸŽŧ They contain methods that **orchestrate the sequence of actions** needed to execute the use case logic. %%% ## How does a Control Object interact with **Boundary** and **Entity** classes? --- 🔄 It **receives input** from Boundary classes, processes it, and interacts with Entity classes to **retrieve or update** data. %%% What defines a **State-dependent** control object? --- đŸšĻ Its behavior depends on its **current state**, and it changes states based on **inputs (events)** from other objects. %%% What is a **Coordinator** control object? --- 🤝 An overall decision-making object that controls others but is **not state-dependent** (e.g., a system scheduler). %%% What is the function of a **Timer** control object? --- ⏱ī¸ It controls other objects on a **periodic basis**, triggered by an external clock. %%% What are the **three types** of Control Objects? --- 1. **State-dependent** (Behavior depends on state). 2. **Coordinator** (Decision making, non-state-based). 3. **Timer** (Periodic triggers). %%% ## What is the primary role of **Application Logic** classes? --- 🧠 They encapsulate the **core functionality, algorithms, and logic** of an application, playing a central role in executing its operations. %%% How do Application Logic classes interact with **Entities** and **Controls**? --- 🔗 They interact with **Entity classes** to retrieve/update data and with **Control classes** to coordinate the flow of system activities. %%% ## What does it mean for Application Logic to be **independent of presentation details**? --- 🏗ī¸ It ensures **separation of concerns**; changes to the User Interface (UI) should not directly impact the core application logic. %%% Why are Application Logic classes used to **partition logic away from data**? --- 🔄 Because **logic is expected to change** more frequently than the underlying data structures. %%% What is the difference between how **Simple** and **Complex Algorithms** are encapsulated? --- 🧮 - **Simple**: Often encapsulated directly within **Entity objects**. - **Complex**: Placed in a **separate class** that interacts with multiple objects (similar to a coordinator). %%% What is the purpose of a **Service** type Application Logic class? --- 🛠ī¸ It provides a **specific service** to other objects, such as reading/writing data or forwarding messages across a network. %%% Which specific object type is the **only** one allowed to communicate with an **Actor**? --- 🎭 **Boundary Objects**. Actors cannot interact with Controllers or Entities directly. %%% What are the communication limits for a **Boundary Object**? --- 🔌 it can only talk to **Actors** and **Controllers**. (It cannot talk directly to Entities). %%% Who are **Entity Objects** permitted to communicate with? --- đŸ“Ļ Only **Controllers** and **other Entity Objects**. %%% Which class acts as the "middleman" that can talk to **Boundary**, **Entity**, and other **Control** objects? --- 🕹ī¸ The **Control** class. (Note: It still cannot talk directly to Actors). %%% Can an **Entity Object** initiate communication with a **Boundary Object**? --- ❌ **No.** Communication between data (Entity) and the interface (Boundary) must be mediated by a **Controller**. %%% Which object types are allowed to communicate with **others of their own type**? --- đŸ‘Ĩ **Entity** objects and **Control** objects. %%% Why is a **Controller** forbidden from talking to an **Actor**? --- 🧱 To ensure **independence from presentation details**; the logic (Controller) should only interact with the interface representation (Boundary). %%% Which types of objects are assumed to be **active (concurrent)** by default? --- 🏃 **All non-entity objects**. Each has its own thread of control and can operate in parallel. %%% What does it mean for an **Entity Object** to be **passive**? --- 🧘 It does not have its own thread; instead, it is **called by active objects** to perform tasks. %%% How does communication differ between **Active** and **Passive** objects? --- đŸ’Ŧ - **Active to Active**: Asynchronous communication. - **Active to Passive**: Synchronous communication (e.g., a standard method call). %%% What is the primary purpose of a **Boundary Object** in the context of the Hardware/Software boundary? --- 🔌 To **abstract away the details** of communicating with the "hardware" side of the interface. %%% Why are **Entity Objects** usually the only passive objects in this architecture? --- 💾 Because their primary role is to **store and manage data** for other active components rather than orchestrating system behavior or timing.