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Chapter 2, image, image - Coggle Diagram

- - - - Concrete Software Architecture
      - Requirement specification
- - - - Signature: the method name plus the list of parameter types
      - Method parameter indicates operation type
      - Usually method invocation
    - - A protocol-based connector can implement multiple operation types with a single binding signature
  - - - If the two elements are mapped to a single process, the connector could be mapped to a local method invocation
      - If the two elements are mapped to two different processes on the same computer, then the connector could be mapped to a local message queue or a pipe
      - If the two elements are mapped to two different computers, then remote method invocation or Web service invocation could be used for the architectural refinement for the corresponding connector between them
    - - Based on Synchronization
        
        Blocking
        
        A blocking connector allows one of its incident elements to send a request to another and wait for a response.
        
        The element will be blocked from further execution until it receives a response.
        
        Non-blocking
        
        A non-blocking connector allows one of its incident elements to send a request to another and continues its execution without waiting for a response.
      - initiator
        
        One Initiator
        
        It only allows one of the two connected elements initiates the request, but not another way around
        
        E.g., web-browser and web server
        
        Two Initiator
        
        either of the two elements can make the request
        
        E.g., call-back between two subsystems, the two subsystems must be connected by a two-initiator connector
      - Information Carrier
        
        Method
        
        Local invocation
        
        Remote invocation
        
        Message (Most Reliable)
        
        A message format must be defined so both the message sender and the message receiver can understand the messages
        
        a protocol must be adopted to decide the proper handshaking and synchronization between the two parties
        
        An example message system, consisting of a message sender module and a message receiver module connected by a network, is used to implement a one-initiator connector for sub-system 1 to send messages/requests to sub-system 2
        
        Global variable
        (Most Efficient)
        
        for elements in the same process
        
        Environment resource
        
        for elements in different processes of the same system
  - - - All element that need be notified of the event will register as listeners of the event source
      - When the event happens, all the registered listener elements will be notified for potential reaction
      - One element will function as an event source
    - - A method call will be made at a time specified at programming time
  - - - Local
      - Network
    - - Distributed Remote Method Invocation (RMI)
      - Remote Procedure Call (RPC)
      - Local method invoacation, function call (local)
    - - Reliability (hard)
      - Security (Problematic, e.g. RPC)
      - Invocation semantics (tricky)
      - However, desperately needed by distributed computing environments.
  - - - 1-1
      - 1-*
    - - Client-server
  - - - both elements must be on the same platform
    - - both elements can be on different platforms
- - - - Public and fixed interface
      - Implementation can change with the time
  - - - Rule 1: Reentrent
        
        describes a computer program or routine that is written so that the same copy in memory can be shared by multiple users
        
        A computer program or subroutine is called reentrant if it can be interrupted in the middle of its execution and then safely called again ("re-entered") before its previous invocations complete executing
        
        A programmer writes a reentrant program by making sure that no instruction modify the contents of variable values in other instructions within the program
        
        Commonly required in operating systems and in applications intended to be shared in multi-use systems
      - Rule 2: Handle Bottle-Neck First
        
        Treat bottle-neck functionality using the following approaches
        
        Wrap it as a separate and highly independent module
        
        Improving its efficiency by replication
        
        Depending on computing needs, allocate cluster or multi-CPU computers for bottle-neck modules in deployment
      - Rule 3: Make Things Simple
        
        If a module is too large
        
        Split it into smaller ones
- - - - These elements may run on the same computer or on multiple computers across a network
      - Software runtime structures serve as the technical backbone of architecture designs and provide the basis from which other structures are derived
      - A runtime project consists of elements:
        
        Processes
        
        Threads
        
        Web services
        
        Distributed objects
      - In this course, we focus on software runtime structures and their efficient mapping to the best implementation technologies.
      - Software Runtime Element
        
        Several code structure elements may implement or support a single runtime element
        
        The same element in a code structure can implement or support multiple runtime elements
      - Run-time Connector Properties
        
        Runtime connectors inherit attributes from their source-code structure counterparts, with a few extra attributes
        
        Distance and connection media
        
        Two connected element may communicate in the same thread, in the same process , on the same computers, or on different computers across a network
        
        Universal invocable
        
        A connector with this attribute set to true allows any external software system to invoke the methods at the connector’s target, irrespective of hardware/software platform, and programming languages
        
        Multiplicity
        
        One element can be connected to multiple elements if it needs to invoke methods of multiple elements at runtime
        
        Self-descriptive
        
        A connector with this attribute set to true allows any external software system to invoke its target method without pre-installation of any software specific to the method.
    - - At software development time
        
        Each modules has assigned functional
        and nonfunctional attributes
        
        API defined for modules separates
        module’s interface and implementation
        
        The main software elements are source code files
        
        The connectors at this level are in
        the form of module dependency
      - Static connectors may exhibit some attributes
        
        Synchronization
        
        Sequence
        
        Direction
      - A software project is typically implemented in multiple files
        
        Binary software component modules
        
        Deployment descriptors
        
        Library files
        
        Others resources files
        
        Executable files
      - Managing Static Structural Representations
        
        It plays a crucial role in the management of large software systems because it deals with the packaging of software modules in order to facilitate system construction and maintenance through a clear portrayal of intermodule relations
        
        Managing static structures involves layers of:
        
        Abstraction for encapsulation
        
        Refinement showing visibility
        
        Static structure affects the architecture's clarity, construction strategy, maintenance, reengineering, reusability…