1. A computer-implemented method for automated discovery and modelling of application services, the method including: (a) for a given application service, identifying a plurality of policies describing software applications upon which the application service depends, wherein the policies include a policy that specifies guidelines to identify, without specifying directly, at least one of the following criteria for a particular application: personal computers having the application loaded; servers having the application loaded; databases accessed by servers having the application loaded; users for personal computers having the application loaded; business units to which users for personal computers having the application loaded are assigned; and network infrastructure that connects together elements described by any of the above criteria; (b) for each policy, identifying a data category, and identifying a collector module for gathering data of that data category; (c) instructing the identified collector modules to gather data; (d) processing the gathered data thereby to create/maintain data objects representing elements that describe, in a specific manner, software applications and information technology infrastructure that supports those software applications, wherein each object is indicative of its relationship with one or more other objects, wherein the relationships include: i. relationships in terms of information technology infrastructure; and ii. business relationships; (e) for each given application service, sorting and manipulating the data objects based on the policies, thereby to create a model for the application service; (f) based on the model, automatically building an end-to-end application service map for each application service; and (g) on the basis of the end-to-end application service map, performing impact prediction analysis in respect of the model, thereby to identify the impact of a failure in respect of an element, in terms of both infrastructure and business impact, wherein the collector modules include Lightweight Directory Access Protocol/Directory Services collector(s) for mapping user, system and account data to common schema, wherein the collector modules include a first collector module that makes use of traffic probing/analysis when identifying inter-application communication, mapping relationships into a common schema.