Abstract:
A method of computing a real estate derivative index value includes: selecting asking rent data; selecting lease rent data; and combining the selected asking rent data and the selected lease rent data to form the index value. The method may further include further combining the combined data with a value representative of general market conditions; forming a composite index of data from plural markets; or computing the index at the end of a time period as:
 
ΔFKI or as ΔRP+ΔCPI+ΔFKI.
 
The method may further include trading based on the index by deriving a trade value from the index value, and executing a trade based on the derived trade value. The method may be carried as instructions on a machine-readable medium and may be carried out using a computer for part or all of the method.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 11/747,874, filed on May 11, 2007, now U.S. Pat. No. 7,974,904 and claims the benefit of U.S. Provisional Application No. 60/887,451, filed on Jan. 31, 2007. The entire disclosures of the above-mentioned earlier applications are hereby incorporated by reference herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a computer system in accordance with an embodiment of the present invention. 
       FIG. 2  is a storage system in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing”, “involving”, and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     According to an exemplary embodiment of aspects of the invention referred to as the Rexx Real Estate Property Index, the Rexx Index calculates Total Return in commercial real estate for the US market based on lease transaction prices, asking rents, Effective Fed Funds, and CPI. The approach is to identify the change in valuation of commercial real estate from current macro and micro economic market conditions as they occur, in contrast to indeterminate average mean sales pairs or lagging appraisals and net income. When Rexx Index returns are benchmarked against indices prepared by Real Estate Investment Fiduciaries and transactional indices from independent research firms, both of which are lagging indicators, the Rexx Index provides a highly-correlated, leading reference point to current market conditions and change in valuation of commercial real estate in individual and broad markets. These results are a function of the data and the Δ Rent Model used in the construction of the Rexx Index which is statistically significant and can be used in all market conditions for all periods in question. 
     The Rexx Real Estate Property Index is based on a Δ Rent Model as explained below, and calculates Total Return, Capital Return and Δ Rent Return for 15 individual markets Atlanta, Boston, Chicago, Dallas, Denver, Houston, LA, NY Midtown, NY Midtown South, NY Downtown, Phoenix, San Francisco, Seattle, Miami, DC, and the broad market Rexx Composite Index. Of course, the selection of individual and composite market compositions is arbitrary and within the skill of the artisan in this field. 
     The Rexx Total Return, Rexx Capital Return, and Rexx Δ Rent Return for Individual Markets and the Rexx Composite Index can be published on any convenient schedule, for example, quarterly in February, May, August and November. 
     If published according to the exemplary schedule, for example, then data collected for the period April, May, and June is published in August, for the quarter period ending June 30th. 
     The Δ Rent Model stands on data which is transparent and statistically significant and can be used in all market conditions for all periods in question. The benefit of the Δ Rent Model is apparent when compared to methods which are moderately successful in the valuation process on a “look back” basis, and are universally accepted to have extreme difficulty in the measurement of current market performance. 
     The Δ Rent Model uses the most fundamental and transparent information which landlords and tenants evaluate supply and demand in the commercial real estate market coupled with the impact of risk premium and cost adjustment to determine total return for the period in question. The Δ Rent Model does not rely on coefficients to offset unknown conditions and free radicals, rolling averages for lack of data, or manipulation of the data set over time. The Δ Rent Model does not rely on NOI, Cap Rate, and Stock Weighting which have proven ineffective in current market valuation. 
     The Δ Rent model determines total return in the commercial real estate market for all periods in questions based on the following assumptions:
         1) Assets that produce risk free rates of return do not increase in value. Assets that produce returns above the risk free rate of return increase in value.   Assets that produce returns below the risk free rate of return decrease in value.   2) Real estate assets provide on-going return based on inflation tied to CPI and other rent escalation clauses.   3) Real estate revenue is dependent upon rent.       

     All data used in the calculation of the Rexx Index is available to the general public, either from public or private sources, some of which may require licenses from their owners. Real estate lease transaction and asking rent data is selected on the basis of specific filters, quality control, and market coverage provided by the leading global real estate brokerage and research firms. Interest rate data is compiled from the US Federal Reserve, and Inflation data is compiled from the US Bureau of Labor Statistics. 
     The Δ Rent Model for all periods in question is based on the equation:
 
Total Market Return=Δ RP+Δ CPI+Δ FKI  
     Δ RP=Risk Premium (∞ Equilibrium−Δ FFR)   ∞ Equilibrium=Average Total Return of Commercial real estate in equilibrium (end.point equilibrium)   Δ FFR=Effective Fed Funds Rate   Δ CPI=Urban Consumer CPI Inflation rate year over year.   Δ FKI=value change based on asking rent and lease transaction pricing of an individual market.
 
∞ Equilibrium is critical to understanding the Δ Rent Model. ∞ Equilibrium is the point when average total return is no longer changing and fixed, for all total return accumulated to ∞/∞, since at this point there are no additional returns to be considered.
   

     In estimating ∞ Equilibrium, long term average total return in commercial real estate has consistently ranged between 8-12%. 
     In the Δ Rent Model, ∞ Equilibrium has been set=10. 
     The functionality and transparency of the Δ Rent model is the ability to measure the impact of macro economic factors in commercial real estate independent from individual market supply and demand conditions.
 
Rexx Capital Return=Δ RP+Δ CPI
     Δ RP=value change from risk premium (∞ Equilibrium−Δ FFR)   Δ CPI=value change from inflation   

     With increases and decreases in the risk premium as measured by Δ RP, the value of commercial real estate increases and decreases in direct relationship for the period in question. With increases and decreases in the rate of inflation as measured by Δ CPI, the value of commercial real estate increases and decreases in direct relationship for the period in question. 
     Individual market performance is subject to micro economic conditions measured in the Δ Rent Model through asking rent and lease transaction pricing. The abundance of information related to these conditions is well documented, and the Δ Rent Model uses data of sufficient market coverage, reliability, and consistent application to determine current market return which includes unforeseen events and natural market trends. 
     Individual Market Δ FKI is calculated as follows:
 
Δ FKI= ( R 1 −R 0)/( R 0)*100
     Δ FKI=value change in commercial real estate from individual market conditions.   R1=ending asking rent and lease transaction pricing for the individual market for the period in question.   R0=beginning asking rent and lease transaction pricing for the individual market for the period in question.   

     Rexx Index (IM) Total Return is calculated from the following equation for all individual markets, for all time periods in question, in all market conditions.
 
Rexx( IM )Total Return=Rexx Capital+Rexx( IM )ΔRent
 
Rexx Capital=Δ RP +ΔCPI
 
Rexx( IM )AERent=Δ FKI  
 
     For example, for Market Index period: 4 qtr 2005:
 
Rexx Chicago Total Return=Δ RP+Δ CPI+ChicagoΔ FKI= 2.965
 
Rexx Capital=2.435 ΔRP= 1.505+ΔCPI=0.93
 
ChicagoΔ FKI= 0.53
 
Rexx Dallas Total Return=Δ RP+Δ CPI+DallasΔ FKI= 4.705
 
Rexx Capital=2.435 ΔRP= 1.505+ΔCPI=0.93
 
DallasΔ FKI= 2.27
 
     The Rexx Index Office Composite includes individual markets with a minimum of 25,000,000 sq ft of Class A office space, a minimum of 100 Class A office buildings, and sufficient research and advisory services to provide reliable reporting of market conditions for the period in question. Other criteria for selecting the individual markets forming the composite may be used. The individual market and composite index selection process does not limit the use of the Δ Rent Model. Other individual market indices and other composite indices corresponding to a different mix of markets or additional markets may be calculated as required. 
     Markets that can be calculated, under the above criteria, include, but are not limited to: 
     Atlanta, Boston, Chicago, Dallas, Denver, Houston, LA, NY Midtown, NY Midtown South, NY Downtown, Phoenix, San Francisco, Seattle, Miami, DC. 
     All Rexx Composite Indices are equal weighted by individual market. The benefit of the Rexx Composite Index weighting allows for individual market comparison to the overall US Market performance, and the ability to measure performance based on individual portfolio holdings per market. 
     The Rexx Δ Rent calculation provides the measure for the supply and demand of all individual markets in the Rexx Δ Rent Composite. Which markets are included in each calculation can be varied, as desired by the index manager. The Rexx Δ Rent Calculation provides the measurement of supply and demand for all individual markets, without macro economic factors, and provides the basis to determine whether an individual market has performed above or below the average benchmark in the US market, and the basis for individual market to market comparison.
 
Rexx Composite Total Return=all individual market Total Returns/number of markets included
 
     In the exemplary embodiment, the number of markets included=15. 
     Trades based on the Rexx index, its components and its composites can be executed using any suitable mechanism. For example, options, futures, swaps and derivatives may all be traded in any suitable market on any suitable exchange. Prediction markets and exchanges, and spread-betting markets and exchanges, are two suitable market/exchange arrangements. These types of trades, markets and exchanges are briefly defined below. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Definitions of Trade Types 
               
             
          
           
               
                 Term 
                 Definition 
               
               
                   
               
               
                 op- 
                 The right, but not the obligation, to buy (for a call option) or sell 
               
               
                 tion 
                 (for a put option) a specific amount of a given stock, commodity, 
               
               
                   
                 currency, index, or debt, at a specified price (the strike price) 
               
               
                   
                 during a specified period of time. For stock options, the amount 
               
               
                   
                 is usually 100 shares. Each option has a buyer, called the holder, 
               
               
                   
                 and a seller, known as the writer. If the option contract is 
               
               
                   
                 exercised, the writer is responsible for fulfilling the terms of the 
               
               
                   
                 contract by delivering the shares to the appropriate party. In the 
               
               
                   
                 case of a security that cannot be delivered such as an index, the 
               
               
                   
                 contract is settled in cash. For the holder, the potential loss is 
               
               
                   
                 limited to the price paid to acquire the option. When an option is 
               
               
                   
                 not exercised, it expires. No shares change hands and the money 
               
               
                   
                 spent to purchase the option is lost. For the buyer, the upside is 
               
               
                   
                 unlimited. Options, like stocks, are therefore said to have an 
               
               
                   
                 asymmetrical payoff pattern. For the writer, the potential loss is 
               
               
                   
                 unlimited unless the contract is covered, meaning that the writer 
               
               
                   
                 already owns the security underlying the option. Options are 
               
               
                   
                 most frequently held as either leverage or protection. As 
               
               
                   
                 leverage, options allow the holder to control equity in a limited 
               
               
                   
                 capacity for a fraction of what the shares would cost. The 
               
               
                   
                 difference can be invested elsewhere until the option is exercised. 
               
               
                   
                 As protection, options can guard against price fluctuations in the 
               
               
                   
                 near term because they provide the right to acquire the underlying 
               
               
                   
                 stock at a fixed price for a limited time. Risk is limited to the 
               
               
                   
                 option premium (except when writing options for a security that is 
               
               
                   
                 not already owned). However, the costs of trading options 
               
               
                   
                 (including both commissions and the bid/ask spread) is higher on 
               
               
                   
                 a percentage basis than trading the underlying stock. In addition, 
               
               
                   
                 options are very complex and require a great deal of observation 
               
               
                   
                 and maintenance. This type of trade is also called option 
               
               
                   
                 contract. 
               
               
                 fu- 
                 A standardized, transferable, exchange-traded contract that 
               
               
                 tures 
                 requires delivery of a commodity, bond, currency, or stock index, 
               
               
                   
                 at a specified price, on a specified future date. Unlike options, 
               
               
                   
                 futures convey an obligation to buy. The risk to the holder is 
               
               
                   
                 unlimited, and because the payoff pattern is symmetrical, the risk 
               
               
                   
                 to the seller is unlimited as well. Dollars lost and gained by each 
               
               
                   
                 party on a futures contract are equal and opposite. In other words, 
               
               
                   
                 futures trading is a zero-sum game. Futures contracts are forward 
               
               
                   
                 contracts, meaning they represent a pledge to make a certain 
               
               
                   
                 transaction at a future date. The exchange of assets occurs on the 
               
               
                   
                 date specified in the contract. Futures are distinguished from 
               
               
                   
                 generic forward contracts in that they contain standardized terms, 
               
               
                   
                 trade on a formal exchange, are regulated by overseeing agencies, 
               
               
                   
                 and are guaranteed by clearinghouses. Also, in order to insure 
               
               
                   
                 that payment will occur, futures have a margin requirement that 
               
               
                   
                 must be settled daily. Finally, by making an offsetting trade, 
               
               
                   
                 taking delivery of goods, or arranging for an exchange of goods, 
               
               
                   
                 futures contracts can be closed. Hedgers often trade futures for 
               
               
                   
                 the purpose of keeping price risk in check. 
               
               
                   
                 This type of trade is also called futures contract. 
               
               
                 swap 
                 An exchange of streams of payments over time according to 
               
               
                   
                 specified terms. The most common type is an interest rate swap, 
               
               
                   
                 in which one party agrees to pay a fixed interest rate in return for 
               
               
                   
                 receiving an adjustable rate from another party. 
               
               
                 deriv- 
                 A financial instrument whose characteristics and value depend 
               
               
                 ative 
                 upon the characteristics and value of an underlier, typically a 
               
               
                   
                 commodity, bond, equity or currency. Examples of derivatives 
               
               
                   
                 include futures and options. Advanced investors sometimes 
               
               
                   
                 purchase or sell derivatives to manage the risk associated with the 
               
               
                   
                 underlying security, to protect against fluctuations in value, or to 
               
               
                   
                 profit from periods of inactivity or decline. These techniques can 
               
               
                   
                 be quite complicated and quite risky. 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Definitions of Market and Exchange Types 
               
             
          
           
               
                 Term 
                 Definition 
               
               
                   
               
               
                 field 
                 A field is a structured space of power and resources with its own 
               
               
                   
                 forms of competition and reward. Markets are an important part 
               
               
                   
                 of fields, but fields are much more than markets: They are also 
               
               
                   
                 made up of agents and organizations and the relations among 
               
               
                   
                 them, of networks and supply chains, of different kinds and 
               
               
                   
                 quantities of power and resources that are distributed in certain 
               
               
                   
                 ways, of specific practices and forms of competition, and so on. 
               
               
                   
                 Each field has a distinctive dynamic that has evolved over time. 
               
               
                   
                 The logic of the field defines the conditions under which agents 
               
               
                   
                 and organizations can participate in the field and flourish or falter 
               
               
                   
                 within it - that is, the conditions under which they can play the 
               
               
                   
                 game. 
               
               
                 market 
                 A market is defined as a place where buyers and sellers get 
               
               
                   
                 together and set prices and quantities. 
               
               
                 exchange 
                 An exchange is an organized market with transactions 
               
               
                   
                 concentrated in a physical facility with participants entering two- 
               
               
                   
                 sided quotations (bid and ask) on a continuous basis. 
               
               
                 prediction exchange 
                 An exchange that organizes prediction markets. 
               
               
                   
                 Synonyms: 
               
               
                   
                 event-driven futures exchange - (U.S.A.); 
               
               
                   
                 event futures exchange - (U.S.A.); 
               
               
                   
                 betting exchange - (U.K., Ireland, Australia); 
               
               
                   
                 person-to-person betting exchange; 
               
               
                   
                 peer-to-peer betting exchange; 
               
               
                   
                 P2P betting exchange. 
               
               
                   
                 Originally, prediction exchanges used real money. 
               
               
                   
                 However, some play-money prediction exchanges have shown 
               
               
                   
                 some form of accuracy. 
               
               
                 betting exchange 
                 (U.K.) Betting exchanges exist to match people who want to bet 
               
               
                   
                 on a future outcome at a given price with others who are willing 
               
               
                   
                 to offer that price. The person who bets on the event happening at 
               
               
                   
                 a given price is the backer. The person who offers the price is 
               
               
                   
                 known as the layer, and is essentially acting in the same way as a 
               
               
                   
                 bookmaker. The advantage of this form of betting for the bettor is 
               
               
                   
                 that, by allowing anyone with access to a betting exchange to 
               
               
                   
                 offer or lay odds, it serves to reduce margins in the odds 
               
               
                   
                 compared to the best odds on offer with traditional bookmakers. 
               
               
                   
                 Exchanges allow clients to act as a bettor (backer) or bookmaker 
               
               
                   
                 (layer) at will, and indeed to back and lay the same event at 
               
               
                   
                 different times during the course of the market. The way in which 
               
               
                   
                 this operates is that the major betting exchanges present clients 
               
               
                   
                 with the three best odds and stakes which other members of the 
               
               
                   
                 exchange are offering or asking for. For example, for England to 
               
               
                   
                 beat Brazil at football the best odds on offer might be 4 to 1, to a 
               
               
                   
                 maximum stake of £80, 3.5 to 1 to a further stake of £100 and 3 to 
               
               
                   
                 1 to a further stake of £500. This means that potential backers 
               
               
                   
                 can stake up to a maximum of £80 on England to beat Brazil at 
               
               
                   
                 odds of 4 to 1, a further £100 at 3.5 to 1 and a further £500 at 3 to 
               
               
                   
                 1. These odds, and the staking levels available, may have been 
               
               
                   
                 offered by one or more other clients who believe that the true 
               
               
                   
                 odds were longer than they offered. An alternative option 
               
               
                   
                 available to potential backers is to enter the odds at which they 
               
               
                   
                 would be willing to place a bet, together with the stake they are 
               
               
                   
                 willing to wager at that odds level. This request (say £50 at 4 to 
               
               
                   
                 1) will then be shown on the request side of the exchange, and 
               
               
                   
                 may be accommodated by a layer at any time until the event is 
               
               
                   
                 over. The margin between the best odds on offer and the best 
               
               
                   
                 odds sought tends to narrow as more clients offer and lay bets, so 
               
               
                   
                 that in popular markets the real margin against the bettor (or 
               
               
                   
                 layer) tends towards the commission levied (normally on winning 
               
               
                   
                 bets) by the exchange. This commission varies from about 2 percent 
               
               
                   
                 to 5 percent. 
               
               
                 spread-betting 
                 An exchange that matches spread bettors. 
               
               
                 exchange 
                 The nature of spread betting is that the more punters are right, the 
               
               
                   
                 more they win, and vice versa. 
               
               
                   
                 A spread bet asks punters to estimate whether a pre-determined 
               
               
                   
                 outcome will be above or below a given range. The potential gain 
               
               
                   
                 or loss depends on how far above or below that range the number 
               
               
                   
                 will be. 
               
               
                 prediction markets 
                 Prediction markets are designed specifically to forecast events. - 
               
               
                   
                 Some are markets designed specifically for information 
               
               
                   
                 aggregation and revelation. Prediction markets are usually 
               
               
                   
                 designed and conducted for the purpose of aggregating 
               
               
                   
                 information so that market prices forecast future events. These 
               
               
                   
                 markets differ from typical, naturally occurring markets in their 
               
               
                   
                 primary role as a forecasting tool instead of a resource allocation 
               
               
                   
                 mechanism. Participants trade in contracts whose payoff depends 
               
               
                   
                 on unknown future events. 
               
               
                   
                 Prediction markets - also called idea futures markets or 
               
               
                   
                 information markets - are designed to aggregate information and 
               
               
                   
                 produce predictions about future events: for example, a political 
               
               
                   
                 candidate&#39;s re-election, or a box-office take, or the probability 
               
               
                   
                 that the Federal Reserve will increase interest rates at its next 
               
               
                   
                 meeting. To elicit such predictions, contract payoffs are tied to 
               
               
                   
                 unknown future events. For example, a contract might pay $100 
               
               
                   
                 if George Bush is re-elected in 2004, or nothing if he is not. 
               
               
                   
                 Thus, until the outcome is decided, the trading price reflects the 
               
               
                   
                 traders&#39; collective consensus about the expected value of the 
               
               
                   
                 contract, which in this case is exactly proportional to the 
               
               
                   
                 probability of Bush&#39;s re-election. 
               
               
                 Information markets 
                 Prediction markets specifically created to aggregate information. 
               
               
                   
                 Such markets usually estimate a probability distribution over the 
               
               
                   
                 values of certain variables, via bets on those values. 
               
               
                   
                 A market designed from the outset for information gathering and 
               
               
                   
                 forecasting is called an information market. Information markets 
               
               
                   
                 can be used to elicit a collective estimate of the expected value or 
               
               
                   
                 probability of a random variable, reflecting information dispersed 
               
               
                   
                 across an entire population of traders. The market prediction is 
               
               
                   
                 not usually an average or median of individual opinions, but is a 
               
               
                   
                 complex summarization reflecting the game-theoretic interplay of 
               
               
                   
                 traders as they obtain and leverage information, and as they react 
               
               
                   
                 to the actions of others obtaining and leveraging their own 
               
               
                   
                 information, etc. In the best case scenario, the market price 
               
               
                   
                 reflects a forecast that is a perfect Bayesian integration of all the 
               
               
                   
                 information spread across all of the traders, properly accounting 
               
               
                   
                 even for redundancy. This is the equilibrium scenario called 
               
               
                   
                 rational expectations in the economics literature, and is the 
               
               
                   
                 assumption underlying the strong form of the efficient markets 
               
               
                   
                 hypothesis in finance. 
               
               
                   
               
             
          
         
       
     
     Several different suitable market structures can be used, including conventional continuous double auction markets, combinatorial information markets and double pari-mutuel markets. 
     Combinatorial information markets use market scoring rules as combinatorial information market makers. 
     Information markets are markets created to aggregate information. Such markets usually estimate a probability distribution over the values of certain variables, via bets on those values. Combinatorial information markets would aggregate information on the entire joint probability distribution over many variables, by allowing bets on all variable value combinations. To achieve this, we want to overcome the thin market and irrational participation problems that plague standard information markets. Scoring rules avoid these problems, but instead suffer from opinion pooling problems in the thick market case. Market scoring rules avoid all these problems, by becoming automated market makers in the thick market case and simple scoring rules in the thin market case. Logarithmic versions have cost and modularity advantages. 
     While a simple information market lets one trade on the probability of each value of a single variable, a combinatorial information market lets one trade on any combination of a set of variables, including any conditional or joint probability. 
     A dynamic pari-mutuel market (DPM) acts as hybrid between a pari-mutuel market and a continuous double auction (CDA), inheriting some of the advantages of both. A DPM offers infinite buy-in liquidity and zero risk for the market institution; like a CDA, a DPM can continuously react to new information, dynamically incorporate information into prices, and allow traders to lock in gains or limit losses by selling prior to event resolution. The trader interface can be designed to mimic the familiar double auction format with bid-ask queues, though with an addition variable called the payoff per share. The DPM price function can be viewed as an automated market maker always offering to sell at some price, and moving the price appropriately according to demand. Since the mechanism is pari-mutuel (i.e., redistributive), it is guaranteed to pay out exactly the amount of money taken in. 
     All the necessary computations to implement the index, its derivatives, trades, and markets and exchanges can be carried out by computer. Embodiments using computers may incorporate systems as now described. 
     Various aspects of some embodiments according to the invention may be implemented on one or more computer systems. These computer systems may be, for example, general-purpose computers such as those based on Intel PENTIUM-type processor, Motorola PowerPC, Sun UltraSPARC, Hewlett-Packard PA-RISC processors, or any other type of processor. It should be appreciated that one or more of any type computer system may be used to perform various trading-related tasks according to various embodiments of the invention. Further, one or more portions of a real estate derivatives trading system may be located on a single computer or may be distributed among a plurality of computers attached by a communications network. 
     A general-purpose computer system according to one embodiment of the invention is configured to perform any of the described functions related to trading real estate derivatives including but not limited to computing values of an index to be traded or components thereof, evaluating a portfolio and changes thereto and communicating trade information between investors and traders. It should be appreciated that the system may perform other functions, including network communication, and the invention is not limited to having any particular function or set of functions. 
     For example. various aspects of the invention may be implemented as specialized software executing in a general-purpose computer system  100  such as that shown in  FIG. 1 . The computer system  100  may include a processor  103  connected to one or more memory devices  104 , such as a disk drive, memory, or other device for storing data. Memory  104  is typically used for storing programs and data during operation of the computer system  100 . Components of computer system  100  may be coupled by an interconnection mechanism  105 , which may include one or more busses (e.g., between components that are integrated within a same machine) and/or a network (e.g., between components that reside on separate discrete machines). The interconnection mechanism  105  enables communications (e.g., data, instructions) to be exchanged between system components of system  100 . 
     Computer system  100  also includes one or more input devices  102 , for example, a keyboard, mouse, trackball, microphone, touch screen, and one or more output devices  101 , for example, a printing device, display screen, speaker. In addition, computer system  100  may contain one or more interfaces (not shown) that connect computer system  100  to a communication network (in addition or as an alternative to the interconnection mechanism  105 .) 
     The storage system  106 , shown in greater detail in  FIG. 2 , typically includes a computer readable and writeable nonvolatile recording medium  201  in which signals are stored that define a program to be executed by the processor or information stored on or in the medium  201  to be processed by the program. The medium may, for example, be a disk or flash memory. Typically, in operation, the processor causes data to be read from the nonvolatile recording medium  201  into another memory  202  that allows for faster access to the information by the processor than does the medium  201 . This memory  202  is typically a volatile, random access memory such as a dynamic random access memory (DRAM) or static memory (SRAM). It may be located in storage system  106 , as shown, or in memory system  104 , not shown. The processor  103  generally manipulates the data within the integrated circuit memory  104 ,  202  and then copies the data to the medium  201  after processing is completed. A variety of mechanisms are known for managing data movement between the medium  201  and the integrated circuit memory element  104 ,  202 , and the invention is not limited thereto. The invention is not limited to a particular memory system  104  or storage system  106 . 
     The computer system may include specially programmed, special-purpose hardware, for example, an application-specific integrated circuit (ASIC). Aspects of the invention may be implemented in software, hardware or firmware, or any combination thereof. Further, such methods, acts, systems, system elements and components thereof may be implemented as part of the computer system described above or as an independent component. 
     Although computer system  100  is shown by way of example as one type of computer system upon which various aspects of the invention may be practiced, it should be appreciated that aspects of the invention are not limited to being implemented on the computer system as shown in  FIG. 1 . Various aspects of the invention may be practiced on one or more computers having a different architecture or components that that shown in  FIG. 1 . 
     Computer system  100  may be a general-purpose computer system that is programmable using a high-level computer programming language. Computer system  100  may be also implemented using specially programmed, special purpose hardware. In computer system  100 , processor  103  is typically a commercially available processor such as the well-known Pentium class processor available from the Intel Corporation. Many other processors are available. Such a processor usually executes an operating system which may be, for example, the Windows 95, Windows 98, Windows NT, Windows 2000 (Windows ME) or Windows XP operating systems available from the Microsoft Corporation, MAC OS System X operating system available from Apple Computer, the Solaris operating system available from Sun Microsystems, or UNIX operating systems available from various sources. Many other operating systems may be used. 
     The processor and operating system together define a computer platform for which application programs in high-level programming languages are written. It should be understood that the invention is not limited to a particular computer system platform, processor, operating system, or network. Also, it should be apparent to those skilled in the art that the present invention is not limited to a specific programming language or computer system. Further, it should be appreciated that other appropriate programming languages and other appropriate computer systems could also be used. 
     One or more portions of the computer system may be distributed across one or more computer systems coupled to a communications network. These computer systems also may be general-purpose computer systems. For example, various aspects of the invention may be distributed among one or more computer systems configured to provide a service (e.g., servers) to one or more client computers, or to perform an overall task as part of a distributed system. For example, various aspects of the invention may be performed on a client-server or multi-tier system that includes components distributed among one or more server systems that perform various functions according to various embodiments of the invention. These components may be executable. intermediate (e.g., IL) or interpreted (e.g., Java) code which communicate over a communication network (e.g., the Internet) using a communication protocol (e.g., TCP/IP). 
     It should be appreciated that the invention is not limited to executing on any particular system or group of systems. Also, it should be appreciated that the invention is not limited to any particular distributed architecture, network, or communication protocol. 
     Various embodiments of the present invention may be programmed using an object-oriented programming language, such as SmallTalk, Java, C++, Ada, or C# (C-Sharp). Other object-oriented programming languages may also be used. Alternatively, functional, scripting, and/or logical programming languages may be used. Various aspects of the invention may be implemented in a non-programmed environment (e.g., documents created in HTML, XML or other format that, when viewed in a window of a browser program, render aspects of a graphical-user interface (GUI) or perform other functions). Various aspects of the invention may be implemented as programmed or non-programmed elements, or any combination thereof. 
     Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.