• Systems Architecture
• : Introduction
• : Processors
• : Input
• : Output
• : Codes
• : Storage
• : Connections
• : System Architecture
• Questions
• : Can you explain architecture in more detail
• : Is it common for people still use UML 1.0
• : what are the major differences between ULM1 and UML2.0
• : Which gives more information for systems architecture: UML 1.* or 2.0
• : In UML 1.* or 2.0, can an artifact be connected to a node
• : in MbariDepolyment.gif, why are there small circles labeled JDBC, RS232, etc
• : What are some other examples of "Executable environments" that nodes represent other than computers and operating systems
• : In both UML1 and UML2 it states there should be no arrows between nodes. However in some of the diagrams where you ask us to distinguish between the two there are arrows; please explain.
• : Is there any other notation besides UML that I can use for system architecture
• : Are UML deployment diagrams a form of data flow diagram
• : What are nodes and artifacts
• : Which one is better a thin client or fat client
• : How do you choose an architecture?
• : What is the architecture you feel is most secure, and why
• Extra -- More on using Pigeons to transmit data
• Review Questions
• Abbreviations

Systems Architecture

Introduction

In this part of the course we look at ways to describe a system in terms of the hardware, software and people in it. We will start by reviewing some of the options for hardware. After that we will look at techniques for documenting many different systems: the current, proposed, planned, and implemented systems.

Physical and Logical Models

Systems Architecture is strongly oriented towards the current and future systems -- how it actually is and how it should be. It defines a Physical model that (hopefully) will implement or realize the more abstract logical models.



We will cover the options for Input, Connections, Output, Storage, and Processors before looking at tools for expressing architectures. First however a problem.

Problem -- Keeping up with new hardware

New hardware appears every month. It pays a computer professional to keep an eye on new developments. I don't know of a really good source on the web.... but I do follow [ http://slashdot.com ] and [ http://www.wired.com ] as straws in the wind.

I subscribe to a blog entitled "Coding Horror" that often has interesting and enlightening comments on software development. As an example, when you have time you check out this article [ 001003.html ] describing the ways in which system and software architecture goes astray and ultimately becomes unmanageable.

A better technique is to join a professional group like the ACM -- Association for Computing Machinery and/or the IEEE-CS -- Institute of Electrical and Electronic Engineers Computer Society.

Both offer student memberships. And discounts if you are a member of the other one. These publish excellent magazines and journals. These, in turn, are available on this campus as electronic digital libraries. On campus, you can check the societies out for nothing at [ http://www.acm.org/ ] and [ index.jsp ] and even drill down into their digital libraries.

Old technology

Be aware that old technology is kept in use for a long time. You are likely to meet examples of old devices [ a3.dotmatrix.html ] still in use in a current system. Always find out why -- sometimes the old device is either the best solution or the only solution to a systems problem. If, and only if, there is no reason -- the old device can become a focus for change.

. . . . . . . . . ( end of section Introduction) <<Contents | End>>

Processors



1. Supercomputer
2. Mainframe...enterprise server
3. Clusters, Grids, Clouds,...: many processors+memories in a tight fast network.
4. Multicore PCS -- several CPUs on one chip. More power with same clock and heat.
5. Many PC's in a rack -- shared display and keyboard.
6. PC -- Personal Computers (Apple ][, IBM PC, ...)
7. Tablets
8. Palmtops (Palm, iPod, ...) and Games
9. Embedded Chip
10. Special purpose processors: GPU (Graphics), Peripherals, ...


1. The key difference to the user is not the hardware so much as the operating system. Here again there is an incredible range of possibilities.

   Operating Systems

   1. Mainframes and Minis had their own special OSs. To find out about these -- ask any faculty member!
   2. UNIX: AT&T, BSD, Linux, ... If you want the history the Wikipedia [ Unix ] article is quite good.
   3. The MS Family: DOS (Disk OS), Windows 3.0, Windows98, Windows2k, Windows XP, Windows Vista, Windows 7, etc. Again, for details (if you want) check out [ Microsoft_DOS ] [ Microsoft_Windows ] on the Wikipedia.

   . . . . . . . . . ( end of section Operating Systems) <<Contents | End>>

. . . . . . . . . ( end of section Processors) <<Contents | End>>

Input

We can classify I/O (Input and Output) devices/options in several ways:
1. Form factor
   • Embedded chip/board or Circuit
   • Cell Phone: may become the one peripheral that everybody in the world owns. Their functionality is increasing under strong competitive pressure. Go to any mall and play with their demo machines! We have had Blackberries and Palm Treos for some time. This appeared 2007 -- UMTS Universal Mobile Telecommunication System [ UMTS ] Now we have Helios, the iPhone, iPod Touch, and Google's new Android (2008)... Hard to tell if which will be the winner and which the whiner!
   • Normal phone
   • Hand Held Device
     • Hand held bar code reader
     • Game controller
     • Palmtop/PDA/cell phone/MP3 player/Zune/...
   • Tablet
   • Laptop/Terminal
   • Workstation/PC
   • Special purpose work station -- eg. Point Of Sale -- -- --(POS)
     

2. Input technology [ Input_device ]
   • Keyboard
   • Radio Frequency IDentification [ RFID ]
   • Micro-technology embedded in bodies: medical uses!
   • Headgear can read eye positions -- either with an infra-red beam or by reading signals to muscles.
   • Sound and (more complex) speech.
   • Body measurements -- Biometrics. These are technologies that extract information by measuring the body. They are mostly used to ID people. They include: finger print and palm print readers, iris scans, retinal scanners, ... The earliest (from Doug Engelbart) was to use people's weight to recognize and log them in!
   • Data capture devices: eg. bar code readers [ Barcode_reader ] [ Barcode ]
   • Digital camera
   • Electronic Whiteboards
   • Graphics
     
     1. Stylus/pen-based
     2. Mouse
     
     
   • Touch screen: Typically you have a screen or tablet plus a special pen. Some use a magnetic pen (WACOM). Special coatings can also be used or a double layers pushed together. A common example is the PalmOS driven devices. I'm not sure how they digitize the pen movements -- but can work well (I have a had a slow spot in one part of the screen or a digitizer that reads taps as strokes and misreads the position on the screen by about 1/10 inches). Notice that some technologies let you use a finger -- very popular for kiosk machines like ATMs and voting, and now the impressive Apple Touch interface. Other manufacturers are introducing their own touch devices.
   • (Magnetic Ink Character Recognition): think checks! [ MICR ]
   • Scanners [ Image_scanner ]
   • OCR::= [ Optical_character_recognition ] -- On a special font it is excellent, and on a fixed known font it is quite good, but scanning regular text with its many fonts, typefaces, wrinkles, defects and so on, OCR only get 80% to 90% accuracy. The key technology is to convert the image into a two-dimensional array of points and try and match parts of it with known templates. There are improvements on this using special data structures and algorithms. I'm not sure where to get the nitty-gritty details. Some forms of OCR input can even handle hand-printed numbers.
   • Cards -- old [ Computer_punch_card ] , new [ Magnetic_stripe_card ] , and smart [ Smart_card ]
   • Phone Keyboard -- 4><12 array of buttons + some special.
   • Voice input and Speech recognition: in my experience flaky and typically needs training. Possible exception: Chinese. Chinese uses inflexions and tone to communicate meaning and voice recognition technology tends to react well to inflection and tone. (A result of a simple experiment at CSUSB CSCI dept in the 1980's). Speech recognition is good way to input data when the hands are busy and the vocabulary is small, fixed, and discrete. Recognizing normal speech is less effective -- and the technology is probably proprietary (= secret). Most techniques are based on separating out the different frequencies of sound that make up the sound: Fourier or Spectrum Analysis. This gives patterns that can be correctly recognized in many cases. However even recognizing where one word begins and another ends in normal speech turns out to be very difficult. It doesn't help that in normal speech we run words together and omit sounds that are supposed to be there. For details try the Wikipedia [ Speech_recognition ]

   • Game controllers: hand held, buttons, joysticks, ... forms of motion sensing, including the Wii Controller
   • Motion Sensing devices: iPod touch, [ Wii_Remote ] [ Wii Dupe.shtml ]
   • Haptic devices -- you hold and manipulate and get force feedback.
   • Manual push buttons, switches, knobs, rollers, etc.
   • CD-ROM -- Compact Disk Read Only Memory, and lately DVD...
   • Sound
   • Many other sensors -- eg. detecting particular molecules, ionization, humidity, pressure, temperature, ... -- all depending on Analog to Digital conversion.

   Principle -- Gather input data as close to its creation as possible

   As a rule -- get the input in to your system as close to where it is created as possible. Collect it automatically if possible. Avoid re-inputting data that can be stored securely. When secure, save information so that it does not have to be re-input. Note: Re-inputting data into a web form is a common design error on web systems.

. . . . . . . . . ( end of section Input) <<Contents | End>>

Output

Here [ Output_device ] is the Wikipdedia summary.
1. Types of Output: audio, fax, COM, COLD, EMail, Internet, Mobile, Special, printers, screens, sound, CD-RW, DVD-RW, ....
2. Special: POS [ Point_of_sale ] , ATMs, special printers, plotters, photos, TVs, VCRs, Toasters, Blinking VCR displays, speakers, and earphones.
3. Screens
4. Printers: laser printer, page printer, line printers, ... [ Computer_printer ] [ Laser_printer ] [ Inkjet ] [ a3.dotmatrix.html ] [ Line_printer ]
5. Special displays: lights, LEDs, LCDs, ...
6. Mobile: cell phone, wireless PDA, ...
7. EMail and Email attachments -- a simple way to get data from a computer to a remote or mobile user.
8. Web page - open and insecure -- Again a simple way to share data that is not particularly secure.
9. COLD [ Computer_Output_to_Laser_Disk ] (the predecessor to the CD-ROM and DVD).
10. CD-ROM, DVDs -- still a developing technology.
11. COM -- Computer Output of Microfilm [ Microfilm ]
12. Fax -- optional printer on many PCs/Macs.
13. Audio -- These days speech is on a chip.

Codes

We will talk more about different ways of encoding data (EBCDIC, ASCII, Unicode, XML, .... ) later in the course.

Storage

The Principle of Locality

Introduction

The principle of locality is one of the most important principles for choosing and organizing data. It relates the design of data processing and software systems to their performance. Quite simply... the closer the data is to where it is processed, the faster the system runs. Similarly, is the sequence of accessing the data moves from one position to a nearby one then the system will run faster. Where data is stored determines how fast it can be found and retrieved. For example, consider a normal telephone directory... It is easy to find the phone number of a person.... but try finding their neighbor's phone number in the phone book. (No! You can't phone up the person and ask them for the name of their neighbor).

Or consider, the old magnetic tape which can retrieve (and write) data very quickly once it starts moving at full speed, and as long as you don't stop it. You can pick up the next piece of data almost instantly, but it takes several minutes to go back to the beginning of the tape, or to the end.

Story -- intern slows down group compilations 100 times

I learned this when I first used a new magnetic tape based compiler in ICI in the 1960's. Suddenly all the compilations in my group were taking 4 or 5 minutes! It turned out that I shouldn't have asked the compiler to compile my program to tape until I had removed all the compile errors. A bug left an incomplete file on the tape and did not write an end-of-tape marker. As a result my compilations (and my group's compilations) involved spooling 200ft of tape to get to the "end". My name was mud! But the compiler team thanked me for finding the bug. And then said "don't do that again!"

Disks

Moving to disks did not change the principle of locality. When the operating system scatters a file all over the disk the computer slows down. This is called fragmentation. We have special programs to defragment disks. But a clever data design can make software run much faster. If the data is read in a sequence that makes the disk head jump at random then each read has an average time proportional to the size of the data set. But, sequential access is faster and depends (on average) on how fast the disk moves.

Networks

The principle of locality also applies to networks. As Admiral Grace Hopper observed light takes 1 nanosecond to travel 11.7 inches. She used to hand out pieces of wire cut to this length. I have one in my offics. She used to observe that even her colleague admirals would understand that there are a lot of nanoseconds from a the ground to a satellite and so one could not instantly communicate with people the other side of the world. The long delay is an example of latency. It can be a major pain in web applications. By the time your server has communicated with the user's client they have lost attention. In some cases it is even worth having multiple copies of the data in many different servers so that it can be delivered rapidly to the processes that need it... but this needs subtle programming to make sure the different copies are synchronized.

As an example if you want to download a copy of Real Player you will be invited to choose the closest of several servers.

Primary Memory and Cache

The principle of locality even holds at the machine code level: (fastest) data in cache vs data in RAM, data in RAM vs data in virtual (disk) memory, ...(slowest).

Conclusion

The principle of locality means that there is a sequence that lets you access the data faster than other sequences. As a result defragmentation is a key way to improve badly designed disk storage systems. Similarly, sorting data is a key technique for improving performance of computer system.

Storage devices -- Size does matter -- faster and smaller .. slower and bigger

The best device depends on many factors -- what you want it to do, cost, size, how much data, how fast, and how reliably, and how mobile, ... What is the best auto? Don't give a Jaguar to a soccer mom!
1. RAM/Primary memory/Core [ Random_access ]
2. Memory chips for cameras and hand held devices.
3. Flash drives -- portable storage of data. [ Flash_drive ] The computer spies best friend. Will fail after a large number of overwrites.
4. Disks -- Direct access -- move head and wait for data to go by. [ Hard_disk ] [ Floppy_disk ] also Zip Disks, etc. Started out the size of a washing machine...
5. Tapes -- Sequential Access -- but fast when you get up to speed. [ Magnetic_tape_data_storage ]

   Data Hierarchy

   1. Data Base -- A collection of linked files -- CMS.
   2. File -- a collection of records of one type -- all the student records we have.
   3. Record -- collection of elements referring to one entity -- Your student record.
   4. Element -- An indivisible atom of information -- example: student Id.

. . . . . . . . . ( end of section Storage) <<Contents | End>>

Connections

Notice that data flows between processes can be internal to a computer or through a network. You can even connect outputs to inputs. However one common and simple improvement to a system is to spot a place where a human re-inputs data that is produced by a computer. This tends to be slow and error-prone and something to be avoided except for a good reason -- like security.

Attributes of connections

You can quantify the behavior of a connection in terms of three key values. Wise computer people tend to think in these terms: Latency, Bandwidth, and Reliability.

Latency is the delay between when a signal/message is sent, and when it arrives. Latency is a time measured in microsecond, milliseconds, seconds, minutes, ...

Bandwidth is a measure of how much data you can transmit in a given time. Typically you have to wait for the first message (Latency) and then the data starts flowing at the rate of the Bandwidth. This is measured in terms of the amount of information that can be sent per unit of time. For example bits per second, bytes per second, ... There is a special unit the Baud that is approximately bits per second. It is said that the Kludge Komputer Korporation had such a bad connections that the salesmen quote the bandwidth in cpf which stood for characters per fortnight:-)

Reliability is a measure of how few errors are introduced when the data is sent through the connection. Also the chance of the connection being broken. Reliability is a complex property with no single measure.


You can trade off reliability with bandwidth be sending redundant data that spots and corrects errors.



Example Communications Link -- Cell Phone

Latency: the time to make the call. Bandwidth: How fast can you talk? Reliability: Distortion, frequencies clipped, Breaking up, bad coverage, dropped calls.

Example Communications link -- campus Wi-Fi

Latency: time to log in and go back to application. Bandwidth: Depends on load and which one you choose -- about 58Kbps -- any exact figires? Reliability: Seems pretty good... what do you think?

Story -- Pigeons as a data connection

For example: A company uses pigeons to take a memory stick from a camera to there home base. Why? OK... the latency is not good.... it take 30 minutes for the pigeon to fly down the Grand canyon. All the company wants is to have the photographs available to the people rafting down the canyon before they get back. But the bandwidth is equal to the size of the memory stick. Reliability? Depends on the presence of hawks!

Exercise -- evaluate some alternative technologies.

Manual Connections

1. Paperwork -- provides a record of the communication. Can be scanned back in or retyped. Not a good idea.
2. Sneakernet -- Copy data to a memory chip/flash drive/floppy/zip/tape/etc and walk it to the other part. Slow, cheap, but reliable!
3. Face to Face.
4. Phone...
5. SKYPE?

Wired Connections

1. A series of "Best technologies" for connecting devices no more than 6 feet apart by wire, like a disk drive and a PC:
   
   1. Ancient Proprietary systems.
   2. Serial -- the venerable RS232 interface and twisted pairs...
   3. Parallel -- the classic Centronics Printer ribbon cable.
   4. Small Computer System Interface [ SCSI ] (pronounced: skuzzy).
   5. Universal Serial Bus [ USB ]
   6. Firewire (The latest IEEE sponsored way of hooking up devices. Examples include cameras to PCs. IEEE 1394. See Wikipedia [ Firewire ] and this IEEE tutorial [ 2.730740 ] )
   7. ...
   
   Ethernet -- a protocol for transmitting data inside a single network. Originally designed for wide area radio networks (eg. Hawai) then adapted to coaxial cables and then to twisted pairs.

   You can biuld an Internet on top of any technology -- even phones and modems. But was originally used to connect ethernets. The Internet is defined by the TCP/IP stack of protocols. TCP defines how to move data and IP defines how to navigate multiple networks. Internet technology is largely defined by the Internet Engineering Task Force [ http://www.ietf.org/ ] (IETF) and the "Requests For Comment" [ http://tools.ietf.org/html/ ] that they archive. There is now a ton of technology that drives the Internet including repeaters, routers, switches, firewalls, Domain Name Servers (DNS), firewalls, and so on.

   WWW -- The World Wide Web is built on top of all the previous Internet technologies...

   VPN -- Virtual Private Network , using encryption to fake an isolated network. The introduction of the VPN technology looks a little fuzzy but the ideas were around in the 1990s and were standardized by 2000. Here is what I dug out of the Internet.

   • VPN's are mentioned and defined in a 1995 editorial by Darren Boulding: [ security.html ]
   • There were IEEE research papers in 1996 [ SDNE.1996.502456 ] and then an editorial [ 2.634834 ] in 1996.
   • The first standard (I can find) is an Internet Request For Comment [ rfc2764 ] posted in February 2000 by Gleeson, et. al.
   • In 2001 Don Hall claimed VPNs were covered by his 1992 US Patent #5,126,728.

. . . . . . . . . ( end of section Wired Connections) <<Contents | End>>

Wireless Connections

1. The security mavin's nightmare.... but so convenient.
2. Blue Tooth for very local connections... Check out [ BlueTooth ] in the Wikipedia when you need details.
3. IEEE 802-11? -- WiFi, WiMax, ... There are a wide array of IEEE standards for wireless connections. See [ 802_11 ] on the Wikipedia for details.

. . . . . . . . . ( end of section Wireless Connections) <<Contents | End>>

Network Topology

The word "Topology" means "the science of position" and in the context of networks indicates the connectivity or structure of the network. So "network topology" is a question of how the parts are connected. We talk about node as the parts and arcs as the connections. More connections mean more money and complexity.... but more connections mean greater reliability:

1. Bus -- High speed backbone with branches. Use to connect peripherals and central processor and memory together inside a single compute.
2. Linear -- simplest, cheapest, and most likely to be separated. Each node connected to one or two neighbors.
3. Star -- A mathematical tree guarantees that there is one path from any node to another. Or none, if the network breaks down.
4. Ring -- Send the token round!
5. Network -- many paths give reliability etc. But costs more. Signals can take the shortest route -- saving time.



Notes on Setting up Reliable Networks

I wrote the following notes in response to a request from a student. I hope they help. However I don't expect you to memorize these hints when I write quizzes and final questions.

1. Get Trained! Take our System Admin sequence: CSCI360, CSCI365, and CSCI366 -- they are part of the new BA program.
2. Abandon any idea of being up-to-date and cutting edge. Remember the bath-tub curve: reliability is best in the middle of a technology's life. The chance of failure is high initially and increases at the end of the life time.

   

   NASA on-board computers are always several generations behind to improve reliability. Best choose things that other people have already had good experiences with. Others can be bleeding edge:-)

3. One the other hand keep your software up to date -- MS products get monthly security patches and anti-virus products seems to update several times a week.
4. Next: how reliable? 365/24/7 is more expensive than 20/6.
5. Reliable cabling: hidden and redundant.
6. Reliable hardware -- and that means a controlled and secure environment. I've known servers to shutdown for an hour once a week when the custodian unplugged it and plugged in a floor polisher! Lock up key servers.
7. Don't forget you will need backup processors and a way to backup and recover data.
8. Then you need to set up redundant servers for running a network: DNS, NIS or LDAP servers, NFS or other file sharing, Web servers, ...
9. All fully up to date with patches if MS, else get the last stable release. Design a system that keeps all MS systems up to date.
10. If you've gone for Wi-Fi then you must secure it. Recall: WiFi works through walls.
11. Then the security system: fire walls (perimeter and between sub networks).
12. Did I mention backing up all the data?
13. Develop admin procedures that monitor and improve reliability.
14. And maintaining a configuration management inventory! What version of each component do you have on each computer.
15. Then train the administrators and set up the panic button schedule: who comes in at 10am at night to reboot the system after a power cut?
16. Then come the client machines. Big question: what hardware and what platform?
17. Then train the users in reliable computing.
18. Did I mention backing up all the data?



. . . . . . . . . ( end of section Connections) <<Contents | End>>

System Architecture

The UML provides a new standard way to describe the architecture of a system: the hardware and the software that it executes. Prior to that there was a branch of flow charting that was used to indicate the physical devices in a system and how they were connected.

Simple UML Deployment Diagrams: hardware and connections

These two figures show the system I used to use up until Summer 2008. And the replacement I am evolving towards. In both diagrams I'm using the old UML1 notation from the old Rational Rose free student edition.





In a deployment diagram there are three-dimensional cubes or boxes called nodes. In the diagrams above they represent hardware devices and computers. Deployment diagrams also show the connections between nodes as simple lines with no arrowheads. Finally the software that is deployed onto the hardware is also shown inside the 3D boxes (nodes). However the notation changed in 2003 from UML1 to UML2.

UML2.0 notation for system architecture -- Deployment Diagrams




Show nodes and artifacts.
Can show the components that are manifested by artifacts.
1. Nodes are 3-D boxes. Artifacts can be listed in the box or shown as rectangles.
2. From the UML2 Language Reference Manual

   

3. A node is something that can execute/run software. It can be hardware or software.
4. Connections between nodes. No Arrows. Just lines marked with the protocol.
5. No connections between artifacts.
6. Nodes represent "Execution environments" including computers and operating systems.
7. Nodes can be put inside nodes to show that one executes the other. For example to show that the client PC executes a browser and a Java Virtual Machine.
8. Artifacts are things that are created: data, programs, scripts, libraries, ...
   Artifacts manifest elements of other models -- components, classes, ...

9. Hardware -> Nodes
10. Op Systems (if special) -> Nodes inside hardware nodes, else use tagged values.
11. Virtual Machines -> Nodes. Example you could show the "Java Virtual Machine" on a PC as the execution environment for compiled Java Applets.
    Data bases executing SQL: SQL artifacts on Data Base node.
12. Browsers that are asked to execute significant scripts and/or applets would also be nodes placed inside hardware. The scripts and applets are shown as artifacts. If the browser executes a virtual machine then this would also be an execution environment. A common example is the JVM -- Java Virtual Machine. Meanwhile on the server one might wish to show Microsoft's Common Language Infrastructure (CLI) as an execution environment for systems that use their .NET Framework.
13. Simple data bases -> artifacts
14. files->artifacts stereotyped <<file>>
15. programs->artifacts stereotype <<process>>

16. The UML defines how symbols in other kinds of diagram are linked to symbols in deployment diagrams. Classes are encapsulated in Components. Components are manifested as artifacts. Artifacts are deployed to nodes.
17. In CS372 we use these diagrams to analyze and design systems. In CS375 we will use them to design software.



The short article [ Deployment_diagram ] on the Wikipedia gives a brief description.

Tagged Values

In the UML you can add constraints to things by using tagged values that look like this

 		{webserver="Apache Tomcat"}

 		{OS="MS XP"}

 		{CPU="Intel ...."}

 		{author=RJB, file="a3.html", source="a3.mth", language="MATHS"}

These are a loose but useful way of supplying data about nodes and artifacts

Stereotypes

You can also attach some useful stereotypes to artifacts. The following are well known
Table

Stereotype	Meaning(UML2)
<<file>>	A physical file in the context of the system developed.
<<script>>	A script file that can be interpreted by a execution environment or node.
<<executable>>	A program file that can be executed on a computer system.
<<library>>	A static or dynamic library file.
<<source>>	A source file that can be compiled into an executable file.
<<document>>	A generic file that is not a source file or executable.


(Close Table)


Example Architectures -- Programming



FYI UML1.* Notation

You may see some of the older style deployment diagrams. So here are the rules:


Show nodes and components.
1. Nodes are 3-D boxes. Components can be listed under the box or shown as rectangles with "tongues" on the left inside the nodes.
2. Computers -> Nodes
3. Special nodes for devices other than computers.
4. Connections between nodes are labeled with protocols. No Arrows.
5. Op Systems shown as components or as a tagged value in a node.
6. Nodes contain Components.
   • Virtual Machines
   • Data bases
   • files
   • programs
7. Connections between components show dependency. You can also show the interfaces provided by the components by lollypops.



Example UML deployment diagrams from a CS372 Project



Which to use -- UML1 or UML2

The web is full of obsolete diagrams. Use UML2 in this class and CS375. The old notation suffers from clutter because it shows both the system architecture and the software architecture (components) on one diagram. UML2 is a less cluttered. It separates the systems architecture (deployment) from software architecture (components). UML1 deployment diagrams could also show devices that where not computers. This feature is missing from UML2 deployment diagrams.

Advice: Only use UML1 if your organization has a policy or standard that you can not change.

Exercise if you have time UML1 vs UML2

Click through to these diagrams I found on the web. [ DemoSysDeploy.jpg ] [ MbariDeployment.gif ] [ deployment-diagram1.png ] [ deployment_diagram.gif ] [ 12779.jpg ] [ way_dep_diagram.jpg ]

Which of the above are ULM1.* and which UML2.0? Which are correct? WHat conclusion can you draw?

Classic Architectures

1. Mainframe plus card input/output and line printers.
2. Mainframe+terminals: A terminal is a special device with limited functions -- a keyboard for input and a screen for display.
3. Mainframe+clients emulating terminals.
4. Stand alone processing. Workstations without connections. Use sneakernet to share data.
5. File sharing: Networked peer-to-peer workstations share data.
6. Client/server: Dedicated server serves many client workstations.
7. Fat and thin clients: A thin client has little special software and can not execute general purpose programs.
8. Multi-tier client/server: Many servers with different functions.
9. Middle-ware: Specialized "Glue" software for connecting tiers.
10. AJAX -- (asynchronous JavaScript and XML) [ AJAX ]

History of CSUSB Student Information Systems Architecture

Even though the functions of the Student Information System have not changed its name and architecture has changed many times.

Architectures:


1. Mainframe+cards and line printer
2. Mainframe running SIS+ with line printer and cards
3. Mainframe running SIS+ with access through a PC running a T3270 terminal emulator.
4. Mainframe running SIS+ and TRACS etc.
5. Mainframe running SIS+ and TRACS and webreg etc.



Currently we have a new architecture -- find out about it on the field trips. Peoplesoft = CMS

Can you explain architecture in more detail

An architecture describes the overall structure of something: the parts and how they are connected. A Systems Architecture describes the hardware and software making up the system. The performance, cost, and reliability of a system is often determined by the architecture. Thus we need to be able to record and evaluate architectures: what software and data is placed where on which hardware.

Architecture is also a process of choosing the parts to meet the requirements of the stakeholders. We will look at this later [ c2.html ] (Choosing an Architecture) + [ r3.html ] (How requirements drive architecture). There will be more in CSCI375.

Is it common for people still use UML 1.0

Yes... but usually because they haven't learned the new standard.

what are the major differences between ULM1 and UML2.0

To get a summary of the differences look at [ ../papers/20050502Abstract.html ] and follow the links into the outline and then to the details.

Which gives more information for systems architecture: UML 1.* or 2.0

They are about the same. Except that the UML1.0 notation is harder to figure out.

In UML 1.* or 2.0, can an artifact be connected to a node

No! Artifacts are placed inside nodes: they are deployed on a node.

in MbariDepolyment.gif, why are there small circles labeled JDBC, RS232, etc

These represent interfaces -- lists of functions that are called/used on one side of the "lollypop" and implemented/provided by code on the other side.

The particular diagram has a problem: it doesn't make clear which component provides the functions and which one uses them. It is better to have a dotted line from the client that uses the interface to the circle indicating it. Then a short solid line (think lollipop) from the interface to the component or class that provides it. The UML2.0 version has a cup for the client but this is hard to draw!

We'll talk more about this notation in CSCI375.

What are some other examples of "Executable environments" that nodes represent other than computers and operating systems

A Java Virtual Machine of JVM.

A Browser that interprets JavaScript.

MySQL.

The .NET runtime environment.

A VB interpreter.

Tomcat Java Server Pages....

ASP -- Active Server Pages.

Interpreters for scripting languages: Perl, Python, Ruby, PHP, Unix shell.

However only show these as nodes if there is something special and unobvious that needs explaining. It is simpler to just mention them as [ Tagged Values ] in the node. Some people just list the internal environments and artifacts inside a node -- with no special notation.

In both UML1 and UML2 it states there should be no arrows between nodes. However in some of the diagrams where you ask us to distinguish between the two there are arrows; please explain.

Many people get this wrong. The result is nonstandard. In your work in this class we will do it right.

Is there any other notation besides UML that I can use for system architecture

Yes. The American National Standard Institute (ANSI) and European Computer Manufacturing Association (ECMA) provide very similar rules for systems architectures. They define special shaped symbols for different devices and connections between them. This is called a Systems Flowchart and here is an example from my Ph. D. Thesis (1971, Brunel University)




1. It shows the British mainframe (ICL 1900) with its magnetic storage, line printer, card reader, and hard disks. I seem to have forgotten the Card Punch -- or else it arrived after I drew the diagram.
2. It shows the ICL 803b with its teletypes, paper tape station, plotter, and a prototype graphical display unit called the ETOM.
3. The two computers were connected by a standard interface -- the British forerunner of the later SCSI.
4. There are also two comments supplying information on the storage available on each machine: 1900: 32K * 24 bits, 803: 8k * 39 bits.
5. There was no standard way to show two-way flows, digitizers, or plotters. I had to fake them.
6. In those days computer people all owned a "Flow Charting Stencil" and a collection of drawing tools. My thesis was about the algorithms and languages needed so that people could draw diagrams using a computer instead. All hail to "MacPaint", "Macdraw", ... "Dia", and even "Visio"!



Here are some of the symbols from that era drawn by the free "Dia" tool.



However Systems Flowcharts do not let you show what is deployed on the hardware or the details (when needed) of the nodes like the UML diagrams. For example, if I drew an UML2 Deployment diagram of the old system it would not show the peripheral devices but it would show the software. The 803 had Algol, SAP, and PictAlgol while the 1900 had FORTRAN, COBOL, and PLAN. The ICL had an Operating System (OS) called George 3 but the 803 had no OS:



(Drawn using the Visio UML2 template by Hruby)

Are UML deployment diagrams a form of data flow diagram

No. They are about the physical connections between hardware and software. DFDs are about the abstract flows of information between abstract processes and data stores.

What are nodes and artifacts

A node is something that can execute code.

An artifact is anything that is made and placed on a computer -- including data, documentation, files, programs, etc.

There is one tough choice: Is an interpreter you must program, an artifact or a node. My answer is only show it as a node if you have an artifact that it will execute it. Then you need a box in which to place the artifact.

Which one is better a thin client or fat client

Depends on the project -- look at the requirements. Look at the properties of the hardware: the clients machine, the connections, the server? How fast are they? Can you easily download the extra software to "fatten the client"?

How do you choose an architecture?

We will cover this in detail later. Right now understand that it is the desired qualities of a system (security, reliability, speed, size, ...) plus the real situation that drive systems architecture.

What is the architecture you feel is most secure, and why

The most secure architecture is a mainframe in a locked room with no connection to the outside world:-)

I think that operating systems that tackled security a long time ago tend to be more secure... especially when they are not the most popular ones. So I like the UNIX based ones. I've had good security experiences with the BSD versions of UNIX from way back.

Linux or Mac X seem to be fairly secure. To make Windows 2K secure is tough if not impossible: I unplug mine from the network whenever I leave the office, and I run a personal firewall, and a virus checker, and the MS updates,... and turn all the software to the most secure properties, and use a suite of tools that encrypts its data...

The most insecure component in any architecture is a foolish person -- fools are too ingenious.

the 11-month-old pigeon, Winston, took one hour and eight minutes to fly the 80 km (50 miles) from Unlimited IT's offices near Pietermaritzburg to the coastal city of Durban with a data card was strapped to his leg.

Including downloading, the transfer took two hours, six minutes and 57 seconds -- the time it took for only four percent of the data to be transferred using a Telkom line.

Further reading [ 25.78.html ] (The Risks Digest).

Review Questions

1. List a dozen Input Devices.
2. List a Dozen Output devices.
3. Compare Blue Tooth with IEEE802-11
4. What options are available for processors?
5. What is the principle of locality?
6. Define latency, bandwidth, and reliability.
7. Which UML diagram lets you describe the hardware and software that is used in a system?
8. What is a Node in the UML?
9. What is an artifact in the UML?
10. Compare and contrast: thin and fat clients.
11. Draw diagrams of the architectures of the systems at CSUSB.
12. Draw a UML2.0 deployment diagram of a web based system where the server uses the JVM to generate pages, and the client is a PC running MS Windows Vista and MS IE6.3.2 with a JavaScript programs. The JavaScript and the JVM use XML to communicate.
13. Find out about AJAX and draw a UML2.0 deployment diagram of it.
14. Translate the following diagram into a series of simple English statements. For example: A is a node connected to .... C is a node that executes ...