Guidelines for Developing a System Architectural Design for a Generic Information Sharing System

Walt Scacchi

M271/F271
Spring 2003

Latest Revision:24 February 2003

Architectural Design Principles

Partitioning Concerns

Scalability: relative ease by which additional system processing capacity, throughput, or transaction can be increased (or decreased) over time.
Replication: Add processing resources that replicate and share part of the workload
Clustering: Physically centralize, but logically distribute processing load
Locality of Decision-Making Authority: distribute the ability to affect modification, while centralizing the decision for which modifications to incorporate
Adaptability/Reconfigurability: Relative ease by which the existing architectural design or configuration of a system can be updated to respond to changing conditions, performance congestion, security attacks, isolate dis-functional sub-systems, etc.
Mitigating Architectural Mis-Matches:

Interface mis-match: example: "I want a plug-in, not a helper application"
Connector mis-match: components cannot interconnect to exchange data
Organizational mis-match: System configuration does not embody/reflect organizational configuration. System "creates" organizational conflicts over responsibility for handling system development, operation or maintenance problems.

Detecting security holes: architectural gaps that allow component dis-function to allow unauthorized access/update to system managed resources.

Partitioning Guidelines

Component-Based: Configure architecture using separable components
Multi-Tier: Configure architecture into tiers that separate user interface, from network access gateways (e.g., Web Servers, security firewalls), from data storage/retrieval repositories (e.g., network file servers, database management system, other back-end servers)

Two-tier: client-server or "time-sharing" (mostly legacy choice)
Three-tier: client-gateway-server (main contemporary choice)
N-tier: client-gateway-gateway-gateway-…-server (main choice in future)
Multi-peer (peer-to-peer): client-client-client-…-client, (e.g., Gnutella, Freenet) or server-server-…-server.

Replicated Multi-Site: Replicate functional components across multiple network sites
Shared Interface: Group components with common interface into single aggregate structure (e.g., a "super-component" or sub-system)
Encapsulation: Group components with heterogeneous interfaces into sub-system with single interface
Reactive Performance Clustering: Monitor system execution performance to determine which components require greatest share of processing or network resources, then reconfigure system architecture (following other partitioning guidelines) to locate high-demand components with high-throughput computers/network bandwidth connections.
Business Process Thread: Gather and cluster components that are related to a business process, in line with other partitioning guidelines.
Locus of modification: Separate components that are likely to undergo continual modification from those that are relatively stable.

The following hyperlinks lead to object templates that constitute an architectural design for an information sharing system. Many template attributes appear in more than one place. When this occurs, the description of the values to be input generally can be found in the System Configuration section.

System Configuration

System Visualization

System Icon

XML Models of Enterprise System Architecture (Optional--Extra Credit)

System Architectural Configuration

System Architectural Configuration specifies all of the component parts and connector pieces interconnected via component-connector interfaces into a whole system.

Every element of your Information Sharing System should be specified with the appropriate descriptive information between the corresponding beginning <tag> and ending </tag>. The indented tags designate the attributes of an element. Only the attributes require entry of descriptive information.

Note descriptive information should be specified for each of the components within <System-Components>. Also, it will often (but not always) be the case that a component has only one type of connector, which provide its inputs and require its outputs.

You will need to make copies of the <Component> template; one copy for each of your system components. Then fill in the required information for each component. For example, if your system has ten components, then your need ten component templates in your system configuration.

Next, the system configuration is primarily a composition of descriptive information in an object-based (or entity-relation) modeling scheme. However, most of the descriptive information you need to fill in should already be described in your System Specification document. Thus, if things work out in a reasonable manner, you should be able to cut and paste the information from your System Specification into the appropriate component attribute fields.

Last, comments in this type font (Times New Roman) in the reusable templates below (in Arial font) should be deleted after you enter the appropriate descriptions. Example values for a given attribute or field in the templates is also shown in Arial font. Example values should also be deleted.

Include a brief narrative description of the system.

</Narrative>

<Host-Id>

For example, http://catalyst.gsm.uci.edu. Otherwise, enter unknown unless you know the current Internet address

</Host-Id>

The name and email address of the person who created this architectural design. For example, Walt Scacchi (wscacchi@uci.edu).

</Author>

A timestamp in the form, year/month/day/hour/minute (e.g., 2003/05/16/21:00), to designate when this system architecture was last updated.

</Version>

<Last-Modified-By>

The name and email address of the person who last modified this architectural design. For example, Walt Scacchi (wscacchi@uci.edu).

</Last-Modified-By>

<System-Components>

For each (software) component in your system, fill in the following component template.

<Component-Identifier> </Component-Identifier>

<Component-Type> </Component-Type>

<Connector-Interface-Type>

Remember, you just enter one of {API, Protocol, Information Bus, ODBC/JDBC, or Other}for each connector interface associated with the current component. Unless you do something ambitious, your most common choices are either API or Protocol. </Connector-Interface-Type>

<Input-Provided-From>

<Component-Identifier>

A system component that provides inputs to this component.

</Component-Identifier>

Each input for a component can be specified using the following template.

<Input-Object>

<Input-Object-Identifier> </Input-Object-Identifier>

<Object-Type>

The object type corresponds to that which can be used to associate the object to a specific application, or to some common MIME object type. For example, for a Catalyst Web page, the object type is HTML, and the associated application may be MS Internet Explorer. </Object-Type> <Object-Attributes>

<Object-Attribute-Identifier>

Insert object attribute name here.

</Object-Attribute-Identifier>

<Attribute-Value-Range>

Insert object attribute value range (e.g., upper and lower bound, if known). If the value range is unknown to you, simply enter unknown. </Attribute-Value-Range>

<Attribute-Exceptional-Values>

Insert object attribute exceptional values. If the exceptional values are unknown to you, simply enter unknown. </Attribute-Exceptional-Values>

</Object-Attributes>

<Object-Error-Signals> Enter description of error signals or messages that are exported by the component if a processing error occurs. If you do not know what kinds of error conditions or signals occur, simply enter unknown. </Object-Error-Signals> </Input-Object>

</Inputs>

</Input-Provided-From>

<Output-Provided-To>

<Component-Identifier>

A system component receiving output from this component.

</Component-Identifier>

Each output can be specified using the following template. Values are similar to those described above for input objects. <Output-Object> <Output-Object-Identifier> </Output-Object-Identifier>

<Object-Type> The object type corresponds to that which can be used to associate the object to a specific application, or to some common MIME object type. For example, for a Catalyst Web page, the object type is HTML, and the associated application may be MS Internet Explorer. </Object-Type> <Object-Attributes>

<Object-Attribute-Identifier>

Insert object attribute name here.

</Object-Attribute-Identifier>

<Attribute-Value-Range>

Insert object attribute value range (e.g., upper and lower bound, if known). If the value range is unknown to you, simply enter unknown. </Attribute-Value-Range>

<Attribute-Exceptional-Values>

Insert object attribute exceptional values. If the exceptional values are unknown to you, simply enter unknown. </Attribute-Exceptional-Values>

</Object-Attributes>

</Outputs>

</Interface>

</Component>

This ending tag denotes the end of the template for one component. Remember, to create and fill-in this kind of template for each system component.

</System-Components>

</System Configuration>

System Visualization

A system visualization is a graphic diagram or system-only rich picture that depicts a visual arrangement of the system components, connectors and interfaces.

A visual diagram for your Information Sharing System should be specified with the appropriate descriptive information between the corresponding beginning <tag> and ending </tag>. The indented tags designate the attributes of an element. Only the attributes require entry of descriptive information.

<System-Visualization>

<Last-Modified-By> </Last-Modified-By>

<! -- Insert a picture or graphic image here> </Graphic>

</System-Visualization>

System Icon

A system icon is an image that denotes a "short-cut" to invoking the system.

A system icon for your Information Sharing System should be specified with the appropriate descriptive information between the corresponding beginning <tag> and ending </tag>. The indented tags designate the attributes of an element. Only the attributes require entry of descriptive information.

<System-Icon>

<Last-Modified-By> </Last-Modified-By>

<Icon>

<! -- insert a picture or graphic icon here>

</Icon>

<System-Invocation>

<! -- insert the system start command or URL associated with the system icon >

</System-Invocation>

</System-Icon>

XML Models of Enterprise System Architecture (Optional--Extra Credit)

Every element of your Information Sharing System should be specified with the appropriate descriptive information.

Name/Identifier for XML Modeling/Design tool used
Author (Corporate/Vendor name)
Version (from Vendor information -- e.g., check "About <tool-name>" for this)
XML description of your project
Project-specific Document Type Definition (DTD)

Cascading Style Sheets (CSS)
XML source for your project
Sample XML presentation views of your project