P67 [def] design activity:
1. Activity that acts as a bridge between requirements and the implementation of the software 
2. Activity that gives a structure to the artifact 
   e.g., a requirements specification 

P68 Two important goals:
1. Design for change (Parnas)
2. Product families (Parnas)

P68 Main Criteria for decomposing a system into modules: Information hiding
    Basis for design (i.e. module decomposition)
    Implementation secrets are hidden to clients
    They can be changed freely if the change does not affect the interface
    Golden design principle

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P70 [def] software design
          software architecture (See P146)
          粗略的结构，如pipeline，blackboard等。而不是在design后对系统的细分
          - Shows gross structure and organization of the system to be defined
          - Often a software architecture is produced prior to a software design

P71 [def] implement

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P78 [def] architectural design, detailed design

P79 [def] Module
   A well-defined component of a software system
   A part of a system that provides a set of services to other modules

P79 hierachy - DAG

P80 USES relation:
A uses B
- A requires the correct operation of B
- A can access the services exported by B through its interface
- it is “statically” defined
- A depends on B to provide its services
  example: A calls a routine exported by B
- A is a client of B; B is a server
- should be a hierarchy

P81 [def] level

P82 keep fan-out low, keep fan-in high

P83 IS_COMPONENT_OF <-> COMPRISES
    IMPLMENTS <-> IS_COMPOSED_OF

P86 interface, implementation

P87 information hiding
    Bad Example: 4.1

P92 Mechanism, Policy

Design Notations:
P94:  Textual Design Notation
P98:  Graphical Design Notation
P143: Unified Modeling Language (for OO)

Categories of Modules:
  P101:
    procedural abstractions
    libraries
    common pools of data
More Abstract:
  P102 Abstract Object (has state)
  P104 Abstract Data Type (exports a type)
  P106 Generic Module (parameterized abstract object or data type)

P111 stepwise refinement:
  A systematic, iterative program design technique that unfortunately may lead to software that is hard to evolve 
  How to transform it into IS_COMPOSED_OF relation (add control flow glue)
  useful in a single module, but not decomposing the large system

P117 Top-down vs. bottom-up
  Information hiding proceeds bottom-up
  Iterated application of IS_COMPOSED_OF proceeds top-down
  in practice, people proceed in both directions (yo-yo design)
  organizing documentation as a top-down flow may be useful for reading purposes

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P119 exception handling

Concurrent Software
P117 monitor based (concurrent accessed objects as passive entities)
P129 rendezvous based (active objects)
*nondeterministic*

P133 real-time software

P139 Middleware
   Layer residing between the network operating system and the application
   Helps building network applications
   Provides useful services
      Name services, to find processes or resources on the network
      Communication services, such as message passing or RPC (or RMI) 
   Corba, a typical standard middleware spec

P140 A further relation - inheritance

P143 - 146 UML notation
  USES relationship is replaced by a variety of relations: inheritance, association, and aggregation.