Chapter 9: Systems architecting: Principles (pt. 1)

ISE 443 / ETM 543

Fall 2013

Architecting a large-scale complex system is the centerpiece of systems engineering

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Recall, from chapter 2, the essential elements of systems architecture: Requirements Mission engineering Requirements analysis/allocation Functional analysis/allocation Architectural design/synthesis System analysis Life-cycle costing Risk analysis Other system/subsystem considerations Formulation of a preferred system architecture

What is a system architecture? NASA defines an architecture as:

How functions are grouped together and interact with each other. Applies to the mission and to both inter- and intra-system, segment, element, and subsystem.

Mission design is viewed in terms of 3 early phases

1. The conceptual design process: Prephase A

2. The mission analysis process: Phase A“The purpose of the Phase A study is to refine the mission and systems(s) requirements, determine a baseline mission configuration and system architecture, identify risks and risk mitigation strategies, identify the “best” candidates, and select one.”

3. The definition process: Phase B

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The DoD provides 3 different views of system architecture The operational architecture view is a description of the tasks

and activities, operational elements, and information flows The systems architecture view is a description, including

graphics, of systems and interconnections The technical architecture view is the minimal set of rules

governing the arrangement, interaction, and interdependence of system parts or elements, whose purpose is to ensure that a conformant system satisfies a specified set of requirements

And provides 6 steps for building an architecture See page 266

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The IEEE definition is simple ...A structure of components, their relationships, and the principles and guidelines governing their design and evolution over time

We can define the process of system architecture using elements 3-10 of the 30 elements of SE (refer back to 7.3.3 – 7.3.10): Requirements analysis/allocation (element 3) Functional analysis/decomposition (element 4) Architecture design/synthesis (element 5) Alternatives analysis/evaluation (element 6) Technical performance measurement (element 7) Life-cycle costing (element 8) Risk analysis (element 9) Concurrent engineering (element 10)

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Your turn ...

Select one of the systems architectures illustrated in the chapter Identify the functional decomposition; that is, state

“function xxx is decomposed into the following subfunctions ....”

Identify the characteristics of a functional decomposition as illustrated in this example

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Characteristics of functional decomposition

Physical facilities at the top level, decomposed to functions and/or other physical facilities

External systems/functions differentiated from internal systems/functions

Use of subsections to group common elements of the system – layering of the elements to represent multiple elements of the same type

Functions/subfunctions connected by arrows indicating direction of information flow

Coding of different types of connections (data types)

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Your turn (again) ...

Look at problem 9.3 on page 301 As a group, agree on the major functions of a

personal computer system Begin the functional decomposition The complete architecture is due on Tuesday,

October 29. This is to be an INDIVIDUAL assignment. You may (but you are not required to) use the work

you did in the group as a starting point, but the final architecture should be your own work.

The final product must be a graphical representation.

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