applications. For this to be effective, either each application must understand how every other application understands/interprets that part of the data that is shared, or there must be a common model of the shared data. To understand this, consider an order handling application which has gone through a process to enter a customer order and where it now needs to send out a bill using application B (a billing system). Application A will have a record of the customer address and it therefore needs to ensure that application B sends the bill to this address. Passing this data between the systems simply requires a common format for the address information – each system needs to expect the same number of address lines, with each line being the same length. That's fairly straightforward. But imagine the difficulty that would occur if the ordering application worked on products that consists of bundles of sub-products (e.g. a broadband access product made from a copper line, a modem, a set of filters and a broadband conversion), whereas the billing application only expected single product/order lines. Trying to convert hierarchical products into non-hierarchical ones without losing information would not be possible. A single information model for data that is shared between applications in this way provides a solution to this problem. The TMF solution to this is called the Shared Information/Data-Model (SID). Common communications infrastructure Through the mid-1980s, computer-based OSSs were developed as stand-alone applications. However, during the early 1990s it became apparent that employing these as purely isolated applications was highly inefficient, since it led to a situation where, for example, orders would be taken on one system but the details would then need to be re-keyed into another in order to configure the relevant network equipment. Major efficiency gains were shown to be available from linking the standalone OSSs together, to allow such features as "Flow-through provisioning", where an order could be placed online and automatically result in equipment being provisioned, without any human intervention. However, for large operators with many hundreds of separate OSSs, the proliferation of interfaces became a serious problem. Each OSS needed to "talk to" many others, leading to the number of interfaces increasing with the square of the number of OSSs. Frameworx describes the use of a Common Communications Infrastructure (CCI). In this model, OSSs interface with the CCI rather than directly with each other. The CCI thus