TECHNICAL FIELD 
     The present invention-relates to an automated exchange system, and in particular to an automated exchange designed to execute orders having a hidden volume. 
     BACKGROUND OF THE INVENTION 
     When trading shares and other financial instruments in an automated exchange, both buyers and seller of course want to get the best possible price. A seller of a particular financial instrument is interested in getting a high price, whereas a buyer is interested in getting a low price. 
     The price is determined by the market. Thus, the price is likely to go up if there are many sellers and few buyers of a particular financial instrument at a particular price, and vice versa. 
     Sometimes a seller or buyer may want to sell/buy a large volume of a particular financial instrument. If the order having the large volume was to be placed in the market as one single order, there is a great likelihood that there would be a negative impact on the market. Thus, the price for that particular financial instrument changes in a direction not wanted by the seller/buyer placing the order having the large volume. See also Schwartz et al: “Next-generation securities market systems: An experimental investigation of quote-driven and order-driven trading”, Journal of Management Information Systems, vol 14, no 2, pp 57-79, 09 1997, ISSN 0742-1222. 
     In order to reduce the impact on the market, it is common that the seller places his selling order in small bits or fractions. In this way only a fraction of the total volume of the order is displayed at each instant. The rest of the order is thus hidden from other investors, and the order is usually referred to as an order having a “hidden volume”. When the whole first fraction has been traded, a second fraction having the same volume as the first fraction is generated and displayed. This pattern is repeated until the entire volume of the order has been traded. 
     In an automated exchange system, there are two main ways of placing orders having a hidden volume. A first way is to manually only enter a small fraction at the time of the order into the automated exchange and wait for that first fraction of the order to be traded before entering the next fraction. The second way is to provide functionality in the automated exchange system that enables trading with a hidden volume in an electronic market. In the second case, the investor enters his order in a conventional way but at the same time he instructs the automated exchange system to handle the order as an order having a hidden volume and also specifies the fraction size. The automated exchange then only displays a fraction of the order at the time, and when the first fraction is traded, the exchange system automatically displays a second identical fraction of the order etc. However, since this is a known way of trading an order having a large volume in an automated exchange other investors are aware that orders having a hidden volume exist. Therefore, when investors observe the behavior of other investors, they can quite easily spot an investor trading an order having a hidden volume, since a new order having the very same size is generated when the first order is traded, although they cannot know the total volume of the order. 
     However, since this is a known way of trading an order having a large volume in an automated exchange other investors are aware of that orders having a hidden volume exist. Therefore, when investors observe the behavior of other investors they can quite easily spot an investor trading an order having a hidden volume, since a new order having the very same size is generated when the first order is traded, although they cannot, know the total volume of the order. 
     The fact that others can detect an order having a hidden volume reduces the positive effect of trading an order with a hidden volume, and the market impact can become significant. 
     SUMMARY 
     It is an object of the present invention to provide an improved computerized trading system for trading orders having a hidden volume. This objects and others are obtained by the present invention as set out in the appended claims. 
     Thus, in an automated exchange system having means for trading an order having a hidden volume, means are provided for receiving an order placed by an investor, the order having a number of parameters associated therewith. The automated exchange system further comprising means for, based on the parameters associated with the order, generating an open volume having a random/pseudo random size and/or at a random/pseudo random time. 
     By generating the open volume with a random/pseudo random size and/or at random/pseudo random times, when trading an order having a hidden volume the risk of others detecting that a large order having a hidden volume has been placed on the market can be significantly reduced. By reducing this risk, the market impact can be shown to be smaller and the investor, i.e. the seller/buyer, can therefore expect to obtain a better price. At the same time the amount of manual labor required for trading the order at a price acceptable for the investor is significantly reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which: 
         FIG. 1  is a general view of an automated exchange system 
         FIG. 2  is a flow chart illustrating different steps performed in the automated exchange system when executing an order having a hidden volume 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In  FIG. 1 , a general view of an automated exchange system is shown. The system comprises a number of remote terminals  10  all connected to a central computer  12  comprising a Central Processing Unit (CPU)  13  and a memory  14  associated therewith. The central computer  12  being loaded with suitable software, such as the SAXESS ® software sold by OM Technology AB, Sweden, forms an automated exchange. The remote terminals are designed to send data to and receive data from the central computer  12 . The terminals  10  are designed to provide an interface for investors, such as broker firms etc., trading financial instruments at the automated exchange. 
     Moreover, the terminals  10  and the computer  12  are designed and configured to exchange data as described below in conjunction with  FIG. 2  when an order having a hidden volume is sent from a terminal  10  to the computer  12 . 
     In  FIG. 2 , a flowchart illustrating different steps performed in the system shown in  FIG. 1  when trading an order having a hidden . . . volume . . . First, in a step  2 C, an order to trade a particular financial instrument, e.g. a share in a particular company is sent from one of the remote terminals  10  to the computer system  12  forming the automated exchange. 
     The order sent in step  20  comprises is associated with a number of parameters. One of the parameters indicate to the computer system  12  that the order is to be traded with a hidden volume, i.e. so that the entire order volume is not displayed at once but only a fraction thereof. In a preferred embodiment the order is also associated with a number of additional parameters indicating how the order having the hidden volume should be traded. 
     The order is received by the computer system  12 , step  21 . The computer system  12 , by reading the parameters associated with the order, identifies the order, step  22 . The computer system  12  then checks if the order is an order that should be traded with a hidden volume, step  23 . If the order specifies trading without a hidden volume the order is treated in a conventional manner as indicated in step  24 . If trading with a hidden volume is indicated, the computer  12  then displays a first fraction of the order, which usually is termed the open volume, step  25 . 
     When the open volume has been traded at the automated exchange formed by the computer system  12 , step  26 , the computer system generates a new open volume, step  27 . The new open volume is generated with a size and at a time being randomized by the computer system  12 . 
     The order can, as described above, be associated with additional parameters. In that case the additional parameters can be used to determine the range within which the size of the open volume, referred to as a fraction of the order, is generated and also the range of the time delay. For example, the user can set a minimum time delay and a maximum time delay. 
     In a preferred example embodiment the user can, for example using a broker work station, not only select the range within which the fractions of the order are to be generated, but also the distribution of the randomly generated fractions. Also, the user can be given the option to set the distribution for the time delays and the range within which the time delays are generated. Suitable distribution functions can for example be a uniform distribution. 
     A new open volume is in this manner generated until the entire order has been traded, steps  28 ,  29  and  30 . 
     Using the trading system as described herein will significantly reduce the amount of manual work required when trading a large order in an automated exchange system. 
     While the present invention has been described with respect to particular embodiments, those skilled in the art will recognize that the present invention is not limited to these specific exemplary embodiments. Different formats, embodiments, and adaptations besides those shown and described as well as many variations, modifications, and equivalent arrangements may also be used to implement the invention. Therefore, while the present invention has been described in relation to its preferred embodiments, it is to be understood that this disclosure is only illustrative and exemplary of the present invention. Accordingly, it is intended that the invention be limited only by the scope of the claims appended hereto.
An automated exchange system for trading an order having a hidden volume. An order is received requesting a hidden volume trade. The automated exchange generates an open volume with a random/pseudo-random size and/or at a random/pseudo-random time based on one or more parameters associated with the order.