SA学习笔记 4 - 2009-11-08 企业架构之应用建模

 Application Model View

 

Application Model

The Application Model describes the application software needed to support the business functions. The three diagrams in the Application Model provide a useful way to capture your system as it is.

It is ideal, particularly for larger projects, to model both the 'as is' and the 'to be' systems. There are some smaller projects, however, which begin with modeling the 'to be' system.

The three diagrams in the Application Model are (from the most general to the most detailed perspective):

• System Context Diagram - a high level Data Flow diagram showing an application with its interfaces to computer systems. It should only show the scope and interfaces of a single release of the application.

• System Area Map - provides a high-level graphical view of your Enterprise's present applications. Compared to other diagrams, the System Area Map has a relatively loose, simple format. Each System Area map should have an Architecture diagram to go with it.

• Rational System Architecture Diagram - gives a high level description of the characteristics of the Applications that satisfy the business requirements. Rational System Architect implements the System Architecture diagram using a Data Flow Diagram format, similar to the System Context diagram.

System Context Diagram

The System Context Diagram is used to set the context of a system in your enterprise that you are modeling. You place one System symbol on the diagram, model the externals and data that the system interfaces with, and generally create one or more child diagrams to show more detail about the system.

You may use the diagram to model existing or future systems and their interfaces -- the scope of the system is that of a single release of a single product.

The basic symbols of the System Conte xt Diagram are:

System Symbol

The diagram's single System Symbol has the same name as the System and release. The scope of the System Symbol includes all processes of the system.

External Symbols

External symbols are outside the scope of the System but interface with it. The External could be another company, agency, or system.

Data Flow Symbols

Data Flows are external interfaces between the External and the Application.

Data Store

A Data Store symbol is where data "rests" when it is neither flowing nor being operated on. A data store can be a database, hard disk, floppy disk, or a file on a disk.

 

System Architecture Diagram

System Architecture Diagram

The System Architecture Diagram enables you to graphically model the applications of a system, and the externals that they interface with and data stores that they use or provide information to.

Application

You use the Application symbol to represent an entire application and graphically show on this diagram how it is related to externals and data stores. Within the application definition, you may specify overall information about the application -- the process threads in the organization that it enables, the type of team effort being used to build it, etc. To specify more details on the implementation of the application, you may create child Data Flow diagrams or UML diagrams, depending on the nature of the application (for example, structured or object-oriented or component-based).

Data Flow

You may model the flow of data as it moves from one point in the system to another with the Data Flow line. The flow may be between externals and applications, or applications and data stores. Within the data flow you may model the data elements and data structures used. Data flows can split into two or more flows, or they can join to one from two or more flows.

Material Flow

You may model the direction of the flow of physical items and materials in the system with the Material Flow line. The flow may be between externals and applications, or applications and data stores.

Data Store

A Data Store symbol is where data "rests" when it is neither flowing nor being operated on. A data store can be a database, hard disk, floppy disk, or a file on a disk.

Multi-Data Store

A Multi-Data Store symbol is used to denote that multiple instances of the data store exists. This convention is used to avoid drawing a copy of a schema for each equivalent data store when you build a data model.

External

An External symbol represents an object that sends information or data to the system, or takes information from the system, but is not itself part of the system.

Multi-External

A Multi-External symbol is used to denote that multiple instances of the external exists.

 

 

System Area Map

System Area Map

The System Area Map provides a high-level graphical view of your Enterprise's present or future applications. Compared to other diagrams, the System Area Map has a relatively loose, simple format. The idea is to show general relationships among application areas without getting into detailed interfaces. Usually the diagram contains lines indicating how data in your current system flows from one application area to another.

Application Area

You may group applications into application areas. The definition of the Application Area symbol contains a list of Actual or Potential applications. Click on the Choices button in the list box to view and drag-and-drop applications that you have modeled into the Actual or Potential Applications list box, or type in the name of new Applications that you think the system will need or has.

Data Store

A Data Store symbol is where data "rests" when it is neither flowing nor being operated on. A data store can be a database, hard disk, floppy disk, or a file on a disk.

Data Flow

You may model the flow of data as it moves between application areas with the Data Flow line. Within the data flow you may model the data elements and data structures used. Data flows can split into two or more flows, or they can join to one from two or more flows.

 

System Structure Diagram

System Structure Diagram

The System Structure Diagram shows the breakdown of the release into physical subsystems.

Module

A Module symbol represents a basic program module. Within Enterprise modeling, the module is described by the Derived Logical Processes (DLPs) it performs.

Transaction Center

A Transaction Center symbol is used to indicate the most important "manager" module. It acts as the focal point of control, doling out the instructions and activating the other modules. This transaction center module is usually placed at the top of the System Structure Diagram, and all other modules hang down from it. It is defined by the Derived Logical Processes (DLPs) it performs.

Library Module

A Library Module symbol is used to represent a function, or segment of code, that will be called by multiple modules. The added time involved in calling an external module is balanced with the efficiency of reusing it many times; it is separated from surrounding code for that purpose. Within Enterprise modeling, you model the Derived Logical Processes (DLPs) the module performs.

Included Module

An Included Module is a module with a distinct identity and function that can be included as part of another module to eliminate the time involved in calling an outside module.

Normal Call

A Normal Call symbol has no indicated frequency and is shown on the diagram as a standard line arrow

Asynchronous Call

An Asynchronous Call occurs only once.

Iterative Call

An Iterative Call is a repeating call, indicated on the diagram with a small curved line at the source, designating a loop.

Data Access

A Data Access symbol is a bold line, without an arrowhead, that displays the access path between a module and some type of data, as in a read, write, or reference to a file.

Stub

A Stub symbol is a dotted rectangular symbol used to display the intention of defining a module without taking the time to actually do it. The stub symbol is a "to be announced" indicator, used during the development of the System Structure chart.

Global Data

A Global Data symbol is a file symbol that can be accessed by any module.

Protected Data

A Protected Data symbol indicates that a file has restricted access. This symbol is used as part of the Information Cluster.

Physical Package

A Physical Package is a rectangular symbol used to indicate the grouping of modules to show that, when implemented, they will perform and be "packaged" as a distinct program.

Data Up & Down

The Data Up symbol is used to indicate that data is traveling from the called module back to the calling module.

The Data Down symbol indicates that data is traveling from the calling module to the called module.

A data flag has an empty circle at its tail.

Control Up & Down

A Control Up symbol indicates that an instruction is traveling from the called module back to the calling module. For example, Procedure A tells Procedure B to execute a task.

A Control Down symbol indicates that an instruction is traveling from the calling module to the called module. For example, Procedure B tells Procedure A to execute a task.

Control flags have filled circles at the tail.

Descriptive Flag Up & Down

The Descriptive Flag Up and Descriptive Flag Down symbols are used primarily for documentation. This is a "high level" indication of the call that eventually will be defined as an explicit data or control flag.