Example: Client

A Client service

Suppose we have a delivery-hub that distributes orders over vendors and registers the subsequent deliveries. Let us define a service for clients, to allow clients to change their name and address and display their orders.
INTERFACE ClientInfo FOR Client,Vendor : I[Client]
BOX [ "Name" : clientName
, "Street" : clientAddress
, "City" : clientCity
, "All orders" : orderedBy~
BOX [ vendor :orderedAt
, product : orderOf
, "Orders to be accepted by provider" : orderedBy~ - V;orderAccepted~
, "Orders pending delivery" : orderedBy~ /\ (V;orderAccepted~ - orderReceived~)
, "Received orders" : orderReceived~


The service has a header, which is the first line in this example:
INTERFACE ClientInfo FOR Client,Vendor : I[Client]
The word ClientInfo is the name of this service. This name identifies the service , so it must be unique throughout the entire context.
This service is shown only to users with roles Client or Vendor. That is indicated by the restriction FOR Client,Vendor. Without that restriction, the service is available for every user in any role.
The term to the right of the colon (:) symbol is called the interface term. A service is called from an atom which must be in the domain of this term. Let, for example, Peter be a Client. As Peter is an element of the domain of I[Client], the service can be called from that atom.
The same term, I[Client], is also used as box term for the box that follows the header. For every element in the codomain of the box term, a container (in HTML: <div>) will be drawn on the user screen. That box serves as a subinterface, which is called with precisely one atom. With I[Client] as box term, the codomain will contain just one atom, which is precisely the atom from which the service was called.
In this example, the outermost box contains seven box items and the innermost box two. Each box item has a label and an term. For example the box item "Name" : clientName has "Name" as its label and clientName as term. The atom a from which the box was called is used to select the pairs (a,x) from the term. All x-es for which (a,x) is in clientName will be displayed. Supposing that the relation clientName associates only one name to a client, this specific box item displays just one name. However, in the fifth box item, the term orderedBy~ - V; orderAccepted~ may contain an arbitrary number of orders to be accepted by provider, all of which are shown.
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A Client service