PATENT ABSTRACT
A method of sorting communication events at a user terminal connected to a communication network and executing a communication client arranged to be operable by a user is provided. The method comprises storing an event list comprising a list of identifiers, each identifier having information relating to at least one previously received communication event associated therewith, wherein the identifier identifies the initiator of the associated at least one previously received communication event and each identifier is listed only once in the list of identifiers. The event list is displayed in a user interface of the communication client. The method further comprises receiving an incoming communication event at the user terminal from an initiating user over the communication network and determining whether the initiating user is present in the list of identifiers stored in the event list. In the case that the initiating user is present in the list of identifiers, the event list is amended by adding information relating to the incoming communication event to the information relating to the at least one previously received communication event associated with the identifier of the initiating user. In the case that the initiating user is not present in the list of identifiers, a new entry is created at the top of the event list comprising an identifier for the initiating user and having information relating to the incoming communication event associated therewith. The display of the event list is updated in the user interface of the communication client.

PATENT DESCRIPTION
RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119 or 365 to Great Britain, Application No. 0807506.1, filed Apr. 24, 2008. The entire teachings of the above application are incorporated herein by reference. 
     TECHNICAL FIELD 
     This invention relates to a communication method and apparatus, particularly but not exclusively for use in packet-based communication systems. 
     BACKGROUND 
     Packet-based communication systems allow the user of a device, such as a personal computer, to communicate across a computer network such as the Internet. Packet-based communication systems include voice over internet protocol (“VoIP”) communication systems. These systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long-distance communication. To use a VoIP system, the user must install and execute client software on their device. The client software provides the VoIP connections as well as other functions such as registration and authentication. In addition to voice communication, the client may also provide further features such as video calling, instant messaging, voicemail and file transfer. 
     SUMMARY 
     One type of packet-based communication system uses a peer-to-peer (“P2P”) topology built on proprietary protocols. To enable access to a peer-to-peer system, the user must execute P2P client software provided by a P2P software provider on their computer, and register with the P2P system. When the user registers with the P2P system the client software is provided with a digital certificate from a server. Once the client software has been provided with the certificate, communication can subsequently be set up and routed between users of the P2P system without the further use of a server. In particular, the users can establish their own communication routes through the P2P system based on the exchange of one or more digital certificates (or user identity certificates, “UIC”), which enable access to the P2P system. The exchange of the digital certificates between users provides proof of the users&#39; identities and that they are suitably authorised and authenticated in the P2P system. Therefore, the presentation of digital certificates provides trust in the identity of the user. It is therefore a characteristic of peer-to-peer communication that the communication is not routed using a server but directly from end-user to end-user. Further details on such a P2P system are disclosed in WO 2005/009019. 
     The client software enables a large variety of different communication events (e.g. voice calls, instant messages, voicemails, video calls and file transfers) to be received at the user terminal of a user from a potentially large number of contacts. It can therefore be difficult for the user to keep track of the ongoing conversations and communication events that are received at the client. 
     The invention seeks to provide a method of sorting communication events at a user terminal that enables the user to readily maintain and access ongoing communications. 
     According to one aspect of the invention there is provided a method of sorting communication events at a user terminal connected to a communication network and executing a communication client arranged to be operable by a user, the method comprising: storing an event list comprising a list of identifiers, each identifier having information relating to at least one previously received communication event associated therewith, wherein the identifier identifies the initiator of the associated at least one previously received communication event and each identifier is listed only once in the list of identifiers; displaying the event list in a user interface of the communication client; receiving an incoming communication event at the user terminal from an initiating user over the communication network; determining whether the initiating user is present in the list of identifiers stored in the event list; in the case that the initiating user is present in the list of identifiers, amending the event list by adding information relating to the incoming communication event to the information relating to the at least one previously received communication event associated with the identifier of the initiating user; in the case that the initiating user is not present in the list of identifiers, creating a new entry at the top of the event list comprising an identifier for the initiating user and having information relating to the incoming communication event associated therewith; and updating the display of the event list in the user interface of the communication client. 
     According to another aspect of the invention, there is provided a user terminal connected to a communication network and executing a communication client arranged to be operable by a user, comprising: a storage means arranged to store an event list comprising a list of identifiers, each identifier having information relating to at least one previously received communication event associated therewith, wherein the identifier identifies the initiator of the associated at least one previously received communication event and each identifier is listed only once in the list of identifiers; a receiving means arranged to receive an incoming communication event at the user terminal from an initiating user over the communication network; a processing means arranged to determine whether the initiating user is present in the list of identifiers stored in the event list, such that, in the case that the initiating user is present in the list of identifiers, the processing means is arranged to amend the event list by adding information relating to the incoming communication event to the information relating to the at least one previously received communication event associated with the identifier of the initiating user, and, in the case that the initiating user is not present in the list of identifiers, the processing means is arranged to create a new entry at the top of the event list comprising an identifier for the initiating user and having information relating to the incoming communication event associated therewith; and a display means arranged to display the event list in a user interface of the communication client. 
     According to another aspect of the invention, there is provided a method of sorting communication events at a user terminal connected to a communication network and executing a communication client arranged to be operable by a user, the method comprising: storing an event list comprising a list of identifiers, each identifier having information relating to at least one previously received communication event and a priority weighting associated therewith, wherein the identifier identifies the initiator of the associated at least one previously received communication event, each identifier is listed only once in the list of identifiers, and the event list is ordered according to the priority weighting; displaying the event list in a user interface of the communication client; receiving an incoming communication event at the user terminal from an initiating user over the communication network; determining whether the initiating user is present in the list of identifiers stored in the event list; in the case that the initiating user is present in the list of identifiers, amending the event list by adding information relating to the incoming communication event to the information relating to the at least one previously received communication event associated with the identifier of the initiating user; in the case that the initiating user is not present in the list of identifiers, determining the priority weighting for the incoming communication event and creating a new entry at a position in the event list in dependence on the priority weighting, the new entry comprising an identifier for the initiating user and having information relating to the incoming communication event associated therewith; and updating the display of the event list in the user interface of the communication client. 
     According to another aspect of the invention, there is provided a user terminal connected to a communication network and executing a communication client arranged to be operable by a user, comprising: a storage means arranged to store an event list comprising a list of identifiers, each identifier having information relating to at least one previously received communication event and a priority weighting associated therewith, wherein the identifier identifies the initiator of the associated at least one previously received communication event, each identifier is listed only once in the list of identifiers, and the event list is ordered according to the priority weighting; a receiving means arranged to receive an incoming communication event at the user terminal from an initiating user over the communication network; a processing means arranged to determine whether the initiating user is present in the list of identifiers stored in the event list, such that, in the case that the initiating user is present in the list of identifiers, the processing means is arranged to amend the event list by adding information relating to the incoming communication event to the information relating to the at least one previously received communication event associated with the identifier of the initiating user, and, in the case that the initiating user is not present in the list of identifiers, the processing means is arranged to determine the priority weighting for the incoming communication event and create a new entry at a position in the event list in dependence on the priority weighting, the new entry comprising an identifier for the initiating user and having information relating to the incoming communication event associated therewith; and a display means arranged to display the event list in a user interface of the communication client. 
     According to another aspect of the invention, there is provided a computer program product comprising program code means which when executed by a computer implement the steps according to the above-described method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and to show how the same may be put into effect, reference will now be made, by way of example, to the following drawings in which: 
         FIG. 1  shows a packet-based communication system. 
         FIG. 2  shows a user interface of a communication client. 
         FIG. 3  shows a user terminal on which is executed a communication client. 
         FIGS. 4A and 4B  shows a contact list user interface of a communication client. 
         FIGS. 5A and 5B  shows a conversation list user interface of a communication client. 
         FIG. 6  shows a flowchart of a method of sorting the entries in the conversation list. 
         FIG. 7A-7C  shows the behaviour of the conversation list with new communication events in a first scenario. 
         FIG. 8A-8C  shows the behaviour of the conversation list with new communication events in a second scenario. 
         FIG. 9  shows the conversation list user interface with an incoming call. 
         FIG. 10  shows the conversation list user interface with a plurality of entries arriving over a period of time. 
         FIG. 11  shows marking an entry in the conversation list as unread. 
         FIG. 12  shows a flowchart of an alternative method of sorting the entries in the conversation list. 
     
    
    
     DETAILED DESCRIPTION 
     Reference is first made to  FIG. 1 , which illustrates a P2P communication system  100 . Note that whilst this illustrative embodiment is described with reference to a P2P communication system, other types of communication system could also be used, such as non-P2P, VoIP systems. A first user of the P2P communication system (named “Tom Smith”  102 ) operates a user terminal  104 , which is shown connected to a P2P network  106 . Note that the P2P network  106  utilises a communication system such as the Internet. The user terminal  104  may be, for example, a personal computer (“PC”), personal digital assistant (“PDA”), a mobile phone, a gaming device or other embedded device able to connect to the P2P network  106 . The user device is arranged to receive information from and output information to a user of the device. In a preferred embodiment of the invention the user device comprises a display such as a screen and a keyboard and mouse. The user device  104  is connected to the P2P network  106  via a network interface  108  such as a modem, and the connection between the user terminal  104  and the network interface  108  may be via a cable (wired) connection or a wireless connection. 
     The user terminal  104  is running a client  110 , provided by the P2P software provider. The client  110  is a software program executed on a local processor in the user terminal  104 . The user terminal  104  is also connected to a handset  112 , which comprises a speaker and microphone to enable the user to listen and speak in a voice call. The microphone and speaker does not necessarily have to be in the form of a traditional telephone handset, but can be in the form of a headphone or earphone with an integrated microphone, or as a separate loudspeaker and microphone independently connected to the user terminal  104 . 
     An example of a user interface  200  of the client  110  executed on the user terminal  104  of the first user “Tom Smith”  102  is shown illustrated in  FIG. 2 . The client user interface  200  displays the username  202  of “Tom Smith”  102  in the P2P system, and the user can set his own presence state (that will be seen by other users) using a drop down list by selecting icon  204 . 
     The client user interface  200  comprises a button  206  labelled “contacts”, and when this button is selected the contacts stored by the user in a contact list are displayed in a pane  209  below the button  206 . In the example user interface in  FIG. 2 , four contacts of other users of the P2P system are shown listed in contact list  208 . Each of these contacts have authorised the user of the client  110  to view their contact details and presence state and mood message information. Each contact in the contact list has a presence status icon associated with it. For example, the presence status icon for “Kevin Jackson”  210  indicates that this contact is “online”, the presence icon for “Maria Jones”  212  indicates that this contact is “not available”, the presence icon for “Roger White”  214  indicates that this contact&#39;s state is “do not disturb”, the presence icon for “Sarah Rowling”  216  indicates that this contact is “offline”. Further presence indications can also be included. Next to the names of the contacts in pane  209  are mood messages  220  of the contacts. 
     The contact list for the users (e.g. the contact list  208  for “Tom Smith”) is stored in a contact server (not shown in  FIG. 1 ). When the client  110  first logs into the P2P system the contact server is contacted, and the contact list is downloaded to the user terminal  104 . This allows the user to log into the P2P system from any terminal and still access the same contact list. The contact server is also used to store the user&#39;s own mood message (e.g. a mood message  222  of the first user  102 ) and a picture  224  selected to represent the user (known as an avatar). This information can be downloaded to the client  110 , and allows this information to be consistent for the user when logging on from different terminals. The client  110  also periodically communicates with the contact server in order to obtain any changes to the information on the contacts in the contact list, or to update the stored contact list with any new contacts that have been added. Presence state information is not stored centrally in the contact server. Rather, the client  110  periodically requests the presence state information for each of the contacts in the contact list  208  directly over the P2P system. Similarly, the current mood message for each of the contacts, as well as a picture (avatar—e.g. picture  226  for “Kevin Jackson”) that has been chosen to represent the contact, are also retrieved by the client  110  directly from the respective clients of each of the contacts over the P2P system. 
     Calls to the P2P users in the contact list may be initiated over the P2P system by selecting the contact and clicking on a “call” button  228  using a pointing device such as a mouse. Referring again to  FIG. 1 , the call set-up is performed using proprietary protocols, and the route over the network  106  between the calling user and called user is determined by the peer-to-peer system without the use of servers. For example, the first user  102  can call a second user “Kevin Jackson”  114 . 
     Following authentication through the presentation of digital certificates (to prove that the users are genuine subscribers of the P2P system—described in more detail in WO 2005/009019), the call can be made using VoIP. The client  110  performs the encoding and decoding of VoIP packets. VoIP packets from the user terminal  104  are transmitted into the network  106  via the network interface  108 , and routed to a computer terminal  116  of the called party  114 , via a network interface  118 . A client  120  (similar to the client  110 ) running on the user terminal  116  of the called user  114  decodes the VoIP packets to produce an audio signal that can be heard by the called user using the handset  122 . Conversely, when the second user  114  talks into handset  122 , the client  120  executed on user terminal  116  encodes the audio signals into VoIP packets and transmits them across the network  106  to the user terminal  104 . The client  110  executed on user terminal  104  decodes the VoIP packets, and produces an audio signal that can be heard by the user of the handset  112 . 
     The VoIP packets for calls between P2P users (such as  102  and  114 ) as described above are passed across the network  106  only, and the PSTN network is not involved. Furthermore, due to the P2P nature of the system, the actual voice calls between users of the P2P system can be made with no central servers being used. This has the advantages that the network scales easily and maintains a high voice quality, and the call can be made free to the users. Additionally, calls can also be made from the client ( 110 ,  122 ) using the P2P system to fixed-line or mobile telephones, by routing the call to the PSTN network. Similarly, calls from fixed-line or mobile telephones can be made to the P2P system via the PSTN. 
     In addition to making voice calls, the user of the client  110  can also communicate with the users listed in the contact list  208  in several other ways. For example, an instant message (also known as a chat message) can be sent by typing a message in box  230  and sending it by selecting the “send message” button  232 . Additionally, the first user  102  can use the client  110  to transmit files to users in the contact list  208 , send voicemails to the contacts or establish video calls with the contacts (not illustrated in  FIG. 2 ). 
       FIG. 3  illustrates a detailed view of the user terminal ( 104 ) on which is executed client  110 . The user terminal  104  comprises a central processing unit (“CPU”)  302 , to which is connected a display  304  such as a screen, an input device such as a keyboard  306 , a pointing device such as a mouse  308 , a speaker  310  and a microphone  312 . The speaker  310  and microphone  312  may be integrated into a handset  112  or headset, or may be separate. The CPU  302  is connected to a network interface  108  as shown in  FIG. 1 . 
       FIG. 3  also illustrates an operating system (“OS”)  314  executed on the CPU  302 . Running on top of the OS  314  is a software stack  316  for the client  110 . The software stack shows a protocol layer  318 , a client engine layer  320  and a client user interface layer (“UI”)  322 . Each layer is responsible for specific functions. Because each layer usually communicates with two other layers, they are regarded as being arranged in a stack as shown in  FIG. 3 . The operating system  314  manages the hardware resources of the computer and handles data being transmitted to and from the network via the network interface  108 . The client protocol layer  318  of the client software communicates with the operating system  314  and manages the connections over the P2P system. Processes requiring higher level processing are passed to the client engine layer  320 . The client engine  320  also communicates with the client user interface layer  322 . The client engine  320  may be arranged to control the client user interface layer  322  to present information to the user via the user interface of the client (as shown in  FIG. 2 ) and to receive information from the user via the user interface. 
     Furthermore, the client engine layer  320  is also arranged to store information relating to communication events received at the client in a storage device  321 . For example, the client engine  320  stores messages (e.g. IM chat messages) as well as information about communication events, such as their sender and the time they are received. The client engine layer  320  is arranged to control the display of information regarding these communication events to the user on the display  304 , and also perform calculations on the information contained therein, as described hereinafter. 
     A communication client may therefore be capable of receiving a variety of different types of communication event. Furthermore, these communication events can often be received contemporaneously, such that, for example, voice calls, IM messages and file transfers are all received in close succession. It can therefore become difficult for the user to manage all the communication events that are happening in the client. This is compounded if the user has a large number of contacts. This is particularly the case when the client is arranged to open a new user interface window for each communication event that is incoming to the client. This can often result in the user having many windows open on his user terminal, each of which can have different communications ongoing with different contacts. This can cause a great deal of confusion to the user, as it becomes hard to manage all the open windows. Frequently, this leads the user to close some of the windows, with the result that the user neglects certain ongoing communications by, for example, forgetting to reply to a message. It is therefore advantageous to have a technique of organising and sorting all the communication events at the client, such the communication events can be much more easily and effectively managed by the user. Such a technique is presented herein. 
     To describe the operation of the method of sorting and arranging the communication events, reference is first made to  FIG. 4A .  FIG. 4A  illustrates the pane  209  of the client user interface, as shown in  FIG. 2 , prior to a communication event being received at the user terminal  104 . The button labelled “Contacts”  206  has been selected such that the full contact list  208  of the user is displayed. 
       FIG. 4B  illustrates the pane  209  of the client user interface following a communication event being received at the user terminal  104 . In this example, a communication event is received from the user “Maria Jones”. This is, for example, an IM chat message, although other types of communication event could also be received. The receipt of the communication event is processed by the client engine  320  and stored in the communication event storage device  321 . The receipt of a communication event is indicated with a marker  402  next to the contact&#39;s name in the contact list  208 . In addition, a button labelled “Conversations”  234  is highlighted, preferably by changing the button&#39;s colour (not illustrated in  FIG. 4B ) and by the addition of a numeric indicator  404  to indicate to the user the number of new communication events that have been received. The “Conversations” button  234  enables the user to view currently active communication events, thereby enabling the user to quickly and efficiently see what communication is ongoing in the client. The operation of the “Conversations” button  234  is described hereinafter. 
       FIG. 5A  illustrates the effect of the user selecting the “Conversations” button  234 . When the “Conversations” button  234  is selected, the contact list  208  is removed from the pane  209 , and replaced by a list of conversations  502  that the user is or has been engaged in using the client  110 . A “conversation” in this context corresponds to an aggregation of the communication events that the user has had (or is having) with a particular contact. For example, the “conversation” stream between the user “Tom Smith” and “Kevin Jackson” (as illustrated in  FIG. 1 ) can comprise a plurality of IM chats, voice calls, file transfers and voicemails sent and received over a period of time. 
     Therefore, a “conversation” for a certain contact is a grouping of all the different types of communication event that has occurred with that contact, sorted by the name of the contact. Information on the conversation stream with a particular contact is accessible to the user by selecting the contact&#39;s name in the conversation list  502 . 
     Therefore, a conversation list is a list of ongoing communications, organised by the names of the contacts with which communications is ongoing. In particular, the name of a contact appears only once in the contact list, and information regarding all the ongoing communications (potentially of different types) with this contact is accessible by the user selecting the name of the contact. An entry for a particular contact is included in the conversation list after receipt of a communication event from the contact, and this entry remains in the conversation list until it is manually cleared by the user. 
     In the case of the example shown in  FIG. 5A , a single communication event has occurred, which is an IM chat received from “Maria Jones”. The numeric indicator  402  on the “Conversations” button  234  indicates that there is one unacknowledged (unread) conversation. The conversation list  502  displays the name  504  of the contact from which the communication event was received and a summary  506  of the communication (e.g. the first line of the IM chat in this example). A further numerical indicator  508  shows the number of unacknowledged communication events that have been received from this particular contact. A date indicator  510  indicates the date on which the communication event present in the conversation list  502  was received. 
     In the specific case of IM chat messages, the further numeric indicator  508  counts the number of individual unread chat messages that are received from a particular contact in a single session. Therefore, the number in the further numerical indicator  508  can be higher than the number shown in the indicator  402  on the “Conversations” button  234 . This is because the number shown in the indicator  402  on the “Conversations” button  234  indicates the total number of unacknowledged conversations, whereas the further numerical indicator  508  indicates the number of unread messages. In other words, the example in  FIG. 5A  indicates that there is one unread conversation, and this conversation comprises three unread IM chat messages. 
     Note that the number shown on the numeric indicator  508  does not only refer to IM chat messages, but represents an aggregate of all other unacknowledged communication events, including further events such as file transfers, voicemails, missed calls and other events. 
     Therefore, when new communication events are received at the client, they are stored in the communication event storage  321  (along with their date and time of arrival) and displayed in the conversation list  502  according to the contact to which they relate. Hence, the information is arranged according to the contact from which the communication event was received, regardless of the type of communication or whether there is a combination thereof. 
       FIG. 5B  illustrates the conversation list  502  after the user  102  has selected the entry from “Maria Jones”. When a conversation listed under a contact&#39;s name in the conversation list  502  is selected, the information related to the communication event is displayed to the user. For example, in the case of the IM chat in  FIG. 5B , the three IM chat messages sent from “Maria Jones” are displayed in another portion of the client user interface (not shown in  FIG. 5B ). Because these messages are now considered to have been read or acknowledged by the user, the look of the entry in the conversation list is changed, preferably so that the summary ( 506  in  FIG. 5A ) is removed. The user can now tell that this entry relates to a conversation that has been read. 
     When an entry in the conversation list  502  has been selected by the user  102 , the further numerical indicator  508  is replaced by a “close” button  512 . The “close” button  502  removes the entry for this contact from the conversation list  502 . This allows the user  102  to manually control which conversations remain in the conversation list (e.g. if they require further action, replies, etc.) and which ones can be removed (e.g. if they have been acknowledged or can be ignored). It should be noted that if an entry is removed from the conversation list  502  using the close button  512 , then the contact is not removed from contact list  208 , and the information regarding the communication event or contained therein may further remain accessible to the user via an additional stored communication history record. 
     Obviously, unless the user is proactively removing entries from the conversation list  502  as soon as they are read, then it will quickly become populated with a large number of contacts from whom communication events have been received, such that it becomes unwieldy for the user to distinguish which communication events are new and need acting upon, and which are old or can be ignored. This therefore becomes similar to a simple history of all communication events received at the client. This has the same problem as the contact list, in that it is difficult to manage the active conversations. A technique for managing the entries in the conversation list  502  to solve this problem is described with reference to  FIG. 6 . 
       FIG. 6  illustrates a flowchart for determining how to sort the entries in the conversations list  502 . Specifically, the flowchart in  FIG. 6  determines where in the conversation list  502  an entry should be placed when a communication event arrives at the client  110 . 
     In step S 602  a communication event is received at the client  110  from a contact of the user  102 . In step S 604 , it is checked whether the incoming communication event relates to a previous entry already present in the conversation list  502 . Preferably, this step checks whether an entry is already present in the conversation list  502  from the same contact as the newly received communication event. 
     If this is not the case, then the incoming communication event requires a new entry in the conversations list  502 . As this is a new entry in the list, it needs to be made prominent to the user. Entries that are at the top of the conversations list are the most prominent to the users, and hence the most likely to be seen and acted upon. Therefore, in step S 606 , the new entry is placed at the top of the conversation list  502 . 
     If the incoming communication event does relate to a previously received communication event that is still listed in the conversation list  502  (e.g. if a new communication event is received from a contact already listed in the conversation list, regardless of whether it is the same type of communication event), then a decision has to be made as to whether to maintain the current entry in its existing position in the list, but update it to indicate a new communication event has been received (i.e. increment the numerical indicator  508  and show the summary  506  shown in  FIG. 5A ), or to move the entry for this contact in the conversation list  502  to the top of the list (and also increment the numerical indicator  508  and show the summary  506  shown in  FIG. 5A ). 
     It is important to appreciate that there is never more than one entry in the conversation list for a particular contact. Therefore, the choice is only whether to move the existing entry in the conversation list or to keep it in its existing position. However, there is a trade-off to be made between moving the entries and maintaining them. Moving an entry to the top of the list makes it more prominent to the user. However, excessive rearrangement of the entries in the conversation list makes it difficult for the user to keep track of where entries are, and hence it becomes more difficult for the user to find a given entry again. 
     In preferred embodiments, to avoid excessive rearrangement of conversation list entries, and the consequential confusion caused to the user, the entry for a particular contact is only moved in the conversation list  502  if a predetermined period of time has elapsed since the previous most recent communication event for that contact was received. In step S 608 , the time of arrival of the new communication event is compared to the time of the previous communication event for this contact. 
     In the case that the time difference between the current and previous communication event for this contact is less than the predetermined period, then, in step S 610 , the position of the contact in the conversation list  502  is maintained (i.e. not moved), but is updated to reflect the new communication event (i.e. incrementing the numerical indicator  508  and adding the summary  506  as shown in  FIG. 5A ). This ensures that when several communication events are arriving from a particular contact in reasonably close succession, the entry in the conversation list  502  is not constantly moving to the top of the list. This is particularly useful in the case that there are further concurrent communication events arriving from other contacts, as this would otherwise result in the entry at the top of the conversation list  502  swapping frequently between the active contacts as the communication events arrived. 
     In the case that the time difference between the current and previous communication event for this contact is greater than the predetermined period, then, in step S 612 , the position of the contact in the conversation list  502  is moved to the top of the conversation list  502 . The entry is also updated to reflect the new communication event (i.e. incrementing the numerical indicator  508  and adding the summary  506  as shown in  FIG. 5A ). 
     Preferably, the predetermined time period above which the entry in the conversation list is moved to the top is one hour. However, the value used can be configurable to any value depending on user behaviour and the types of communication events that can be received at the client  110 . 
     The operation of the flowchart in  FIG. 6  is further illustrated with reference to  FIGS. 7A-C  and  8 A-C. Reference is first made to  FIG. 7A , which illustrates the conversation list  502  shown in the pane  209  in the state as shown in  FIG. 5B , such that a communication event (in this case in IM chat message) has been received from “Maria Jones” and read by the user. In addition, a further new communication event has been received from a different contact, “Roger White”. 
     Because there is not a previous entry in the conversation list  502  for “Roger White”, then the result of the analysis in step S 604  is negative and the entry  702  is displayed at the top of the conversation list  502  (step S 606 ), as illustrated in  FIG. 7A . The entry  702  for “Roger White” also has a summary  704  and a numerical indicator  706  showing the number of unacknowledged communication events, in order to indicate to the user that there are unread/unacknowledged communication events from this contact. 
     In  FIG. 7B , time has passed since the communication event from “Roger White” arrived. Specifically, the user has viewed the message from “Roger White” by selecting the entry  702  in the conversation list  502 , such that only his name is now displayed (i.e. the summary  704  and indicator  706  are removed), and sufficient time has elapsed such that the communication events from “Roger White” and “Maria Jones” are shown as having been received yesterday by date indicator  510 . In particular, the time elapsed since the last communication event from “Maria Jones” is greater than the predetermined time in step S 608 . 
       FIG. 7C  shows the situation where, following the elapsed time, an additional communication event has been received from “Maria Jones”. Because there is already an entry  504  in the conversation list  502  for “Maria Jones”, the result of the analysis in step S 604  is positive, and the time difference between the new and previous communication event of “Maria Jones” is considered in step S 608 . As stated above, this is greater than the predetermined time period. Therefore, according to step S 612 , the entry  504  for “Maria Jones” is moved to the top of the conversation list  502 , as illustrated in  FIG. 7C . The presence of an unread communication event is indicated to the user by the addition of summary line  708  and a numerical indicator  710  to show the number of unacknowledged communication events from this contact. Indicator  402  is also incremented. The date indicator  510  now shows that the communication event from “Maria Jones” was received today. An additional date indicator  712  is therefore required for yesterday, under which the entry for “Roger White” remains. 
     An alternative scenario is illustrated with reference to  FIGS. 8A-8C .  FIG. 8A  shows an identical scenario to  FIG. 7A , in that a communication event has been received from “Roger White” which is placed at the top of the conversation list  502 .  FIG. 8B  shows a similar scenario to  FIG. 7B  described above, except that a shorter period of time has elapsed. In particular, the time that has elapsed since the arrival of the communication event for “Maria Jones” at entry  504  in the conversation list  502  is less than the predetermined time period of S 608 . Note that (in comparison to  FIG. 7B ) the date indicator  510  still reads “today”. 
       FIG. 8C  shows the situation where, following the elapsed time, an additional communication event has been received from “Maria Jones”. Because there is already an entry  504  in the conversation list  502  for “Maria Jones”, the result of the analysis in step S 604  is positive. The time difference between the new and previous communication event of “Maria Jones” is considered in step S 608 , which is, as stated above, less than the predetermined time period. Therefore, according to step S 610 , the entry  504  for “Maria Jones” is maintained in its current position (and not moved to the top of the conversation list  502 ) as illustrated in  FIG. 8C . The presence of an unread communication event is indicated to the user by the addition of summary line  802  and a numerical indicator  804  to show the number of unacknowledged communication events from this contact. Indicator  402  is also incremented. 
     Therefore,  FIGS. 7A-7C  illustrate the case where a communication event is received, and the time elapsed since the previous communication event from that contact was received is greater than a predetermined period, and  FIGS. 8A-8C  illustrate the case where the time period is less than a predetermined period. This technique ensures that entries in the conversation list are not moved around unnecessarily, thereby increasing the usability of the conversation list. 
     Reference is now made to  FIG. 9 , which illustrates a further enhancement to the operation of the conversation list sorting technique shown in  FIG. 6 . Certain communication events have the specific property that they need to be acted on immediately. An example of this is a voice call. If a voice call is received at the client, the user needs to answer it within a short period of time, as otherwise the calling user will hang-up or be diverted to the called user&#39;s voicemail. Other examples of this type of communication event are a video call or a voicemail. It is therefore desirable to ensure that these communication events are brought to the user&#39;s attention immediately, regardless of how recently a previous communication event from this contact was received. As a result of this, the flowchart of  FIG. 6  can be modified to assess the type of communication event, such that if the communication event is an incoming call (voice or video) or voicemail then an entry in the conversation list is always placed at the top of the list. This is illustrated in  FIG. 9 , where a notification of an incoming call from “Sarah Rowling” is displayed at the top of the conversation list  502  with an appropriate icon  904 . 
     Furthermore, if an incoming call is unanswered, then an entry is placed in the conversation list  502  to notify the user of a missed call. Preferably, this type of event is also always placed at the top of the conversation list in order to increase its prominence to the user. However, in alternative embodiments, the time difference elapsed since the last communication event with this contact can be taken into account. 
       FIG. 10  illustrates a conversation list  502  comprising several communication events from different contacts that have occurred over a period of time. In particular,  FIG. 10  shows a set of 17 unread IM chat messages from “Maria Jones” ( 1002 ); a file transfer from “Roger White” ( 1004 ); a missed call from “Sarah Rowling” ( 1006 ); and a communication event from “Kevin Jackson” ( 1008 ) that has been selected and read by the user.  FIG. 10  further illustrates how the entries in the conversation list  502  are divided up into a plurality of time categories ( 1010 ,  1012 ,  1014 ), such that a degree of chronology for the arrival of the communication events can be discerned by the user. Note however, that whilst these time categories do indicate the date on which a communication event was received, the individual entries within a single date are not necessarily in a precise chronological order, as they may or may not be moved within the conversation list depending on the time interval between subsequent communication events from a given contact (as described with reference to  FIG. 6 ). Therefore, the conversation list  502  does not represent merely a chronological history of communication events. 
       FIG. 10  illustrates a selection of the types of communication event that can be shown in the conversation list. In particular, the conversation list  502  can include entries relating to the following communication events received at the client:
         Missed calls;   New voicemails;   IM chat message received;   Incoming file transfer;   Incoming authorisation request (i.e. from a person not yet in the user&#39;s contact list);   Authorisation request accepted (i.e. a person has accepted a request for authorisation originating from the user of the client);   Third party alerts (e.g. alerts from a payment provider); and   Contact alerts (e.g. it is a contact&#39;s birthday).       

       FIG. 11  illustrates a further feature of the conversation list  502 . Once the user has selected an entry in the conversation list  502 , the entry is shown as read/acknowledged. However, after initially viewing the entry in the conversation list, the user may wish to act further on this communication event (e.g. by sending an IM message reply, or returning a voice call). In order to highlight the fact that the communication event requires further action, the user can select the entry in the conversation list such that a menu of options  1102  is displayed. One of these options is “Mark as unread”  1104 . When this option is selected, an indictor  1106  is placed next to the entry in the conversation list  502  in order to highlight it to the user. The indicator is similar to the numerical indicators displayed for new communication events (such as indicator  508  of  FIG. 5A ). Marking a conversation as unread shows the number of communication events that were present before the entry was selected (i.e. marked as read). This means that if an entry in the conversation list had five unread communication events before being selected, then selecting the entry clears the numerical indicator  508  showing “5”, and subsequently marking the entry as “unread” (with option  1104 ) restores the numerical indicator  508  showing “5”. This therefore enables the user to rapidly see entries in the conversation list that are marked as requiring further attention (i.e. are unacknowledged), thereby ensuring that important communication events are not forgotten about or ignored. 
     In a further embodiment of the invention, the ordering of the entries in the conversation list can be based upon a weighting value assigned to each entry, such that the weighting value denotes a level of importance or priority to the entry. For example, communication events received from certain people can be more important to the user than others. It is therefore useful for the user to be able to assign importance or priority weightings to particular contacts in the contact list  208 . Such importance or priority weightings can take the form of simple “low”, “medium” or “high” weightings, or can be more precise, in the form of a one to ten rating. These weightings are set by the user and stored at the user terminal. Each contact will also have a default weighting, in case the user does not explicitly set a weighting. This can be, for example, a weighting of “medium” importance. 
     Once the weightings are defined for the contacts, the ordering of the conversations list is performed according to the flowchart shown in  FIG. 12 . In S 1202  an incoming communication event is received at the user terminal. In S 1204  it is determined whether the incoming communication event relates to a previous entry already present in the conversation list  502 . Preferably, this step checks whether an entry is already present in the conversation list  502  from the same contact as the newly received communication event. 
     If the communication event does not relate to a previous entry in the conversation list, then in step S 1206  a weighting of the importance of the communication event is determined. This is performed by looking up the weighting value for the identity of the contact associated with of the communication event. In step S 1208  a new entry is created in the conversation list. However, unlike in  FIG. 6 , in step S 1208  this is not always placed at the top of the list. Rather it is placed according to the weighting value, such that it is below entries with a higher importance weighting, but above those with a lower importance weighting. Therefore, the highest priority events are at the top of the conversation list, and the lowest priority events are at the bottom of the conversation list. In this way, new events from contacts that are deemed less important are not made as prominent to the user, whereas ones that are deemed very important are made most prominent as they will be placed at the top of the conversation list. 
     Note that there can be situations where several events are in the list with the same weighting value (particularly if simple “low”, “medium” and “high” categories are used). In this case, the newest entries are preferably placed at the top of the older entries having a given priority weighting. However, in alternative embodiments, other contention mechanisms can be used, such as placing the entries in alphabetical order. 
     Returning again to step S 1204 , if the communication event does relate to a previous entry in the conversation list, then in step S 1210  it is checked whether the weighting value for this contact remains consistent with the current position of the event in the conversation list. This can occur because the user can change the importance weighting for a given contact between receiving communication events. For example, if the user is expecting to receive an important communication event from a particular contact, then he can increase the importance weighting to “high” in order to ensure that he does not overlook the communication event. 
     If the weighting value remains the same for the communication event then, in step S 1212 , the position of the entry in the conversation list is maintained, but updated to reflect the new communication event (as was shown with reference to  FIG. 8C ). 
     If the weighting value has changed, then in step S 1214 , the position of the entry in the conversation list is updated to reflect the changed weighting in a similar manner to the positioning of the new event in S 1208 . Specifically, the event is moved such that it is below entries with a higher importance weighting, but above those with a lower importance weighting. As described above, a contention mechanism is used when there are multiple entries with the same weighting value, such as placing the most recently received events above older events with the same weighting. 
     The flowchart in  FIG. 12  therefore provides a technique by which a conversation list can be ordered such that communication events deemed to have a higher importance than others are made more prominent to the user. 
     In yet further embodiments, different measures of the weighting value can be used in combination with the flowchart of  FIG. 12 . For example, rather than associating a weighing of importance to the identity of a contact, difference weightings can be associated to different types of communication event. For example, communications events such as missed voice or video calls can be given “high” priority, instant messaging can be given “medium” priority, and other events such as file transfers can be given “low” priority. The operation of the flowchart of  FIG. 12  is then identical, but the ordering of the conversation list now depends on the type of communication event received. For example, following the receipt of IM messages from a contact, then there is an entry in the conversation list for this contact. After a period of time and the receipt of other messages from other users, this entry is located in the middle of the conversation list. However, if there is a missed call from this contact, then this has a higher priority weighting than IM messages, and the entry is moved to the top of the list. 
     Furthermore, the importance weighting for a communication event can also be dependent on the contents of the communication event itself. For example, the user can define certain words as being a trigger for important messages. Therefore, the user defines a list of words and associates a particular priority weighting with each of these words. The contents of a message are compared to the trigger words, and any messages containing these words are given the associated weighting. 
     This can be of particular use with regards to setting the weighting of IM messages, where the contents of the messages are simple text. However, it can also be used for file transfers, by utilising the contents of the file or the filename, or for voicemails by utilising speech recognition technology. This can also be used in combination with any of the previous techniques for ordering the conversation list, to give an additional level of accuracy to the ordering of the entries in the conversation list. 
     While this invention has been particularly shown and described with reference to preferred embodiments, it will be understood to those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appendant claims.