Chris Russell O2.41d 02920 41 6431 crussell@cardiffmet.ac.uk Business Analysis Entity Life History Chris Russell O2.41d 02920 41 6431 crussell@cardiffmet.ac.uk Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Session schedule Business Analysis Schedule Academic Year 2014-5 Semester 2 Week Topic 1 Introduction 2 Investigate situation: rich picture, context diagrams 3 Consider perspectives: types of participation, CATWOE, Power-Interest, Thomas-Kilmann 4 Analyse needs 1: Use Cases 5 Analyse needs 2: structured techniques 6 Define requirements 1a: SSADM 7 Define requirements 1b: SSADM EASTER 8 Define requirements 2: UML 9 Generic assignment feed-forward and task review 10 Balance good enough software against quality costs; Prioritise requirements 11 Assignment submisison Lecture BA14 Entity Life History

Activities and Paradigms Investigate Situation Consider Perspectives Analyse Needs Define Requirements Socio-technical Rich picture CATWOE Types of participation Thomas-Kilmann Power-Interest X Functional Level 0 diagram Structured techniques DFD, ERM and ELH Object-Oriented Context diagram Use Cases Class and Sequence diagrams Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Contents Mapping functions to entities Entity Life History constructs: Sequence Iteration Selection Constructing an Entity Life History Advanced features of Entity Life Histories Entity Life Histories in Select Logical Data Structures in Select Lecture BA14 Entity Life History

Mapping functions to entities Entity Life Histories enable functions (taken from the DFD) to be mapped against entities (taken from the LDS) In addition, they represent the key features of structured decision techniques: Sequence Iteration Selection Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Sequence All ELHs will contain a sequence of events, read from left to right. The first event will always show the creation of the entity, and the last box will show the event which deletes the entity.   Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Iteration   Iterations are used to illustrate cases where an event can effect an entity occurrence more than once and is represented by an asterisk in the top right hand corner of the box. Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Selection This indicates a choice between more than one event and is indicated by a circle in the top right hand corner of the box. Lecture BA14 Entity Life History

Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Selection can also be used to illustrate optional effects by employing a null box.   Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Development of ELH The development of entity life histories is carried out in the following stages:   identify an initial list of events which affect the entities  using the LDS diagram as a reference point, document the effect of those events on each entity Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Stage 1 involves the creation of a matrix which cross refers entities to the events which effect them. The list of entities forms one axis of the matrix and is taken from the logical data model of the system. The list of events forms the other axis and this comes from the functions in the system (from the DFD). For every entity in the matrix, it is necessary to determine whether an event creates, modifies, or deletes the entity, and this is entered on the matrix as C (create), D (delete) or M (modify). Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Entity/Event matrix Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Stage 2 involves developing the ELH for each entity.   Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Checking the matrix When the entity/event matrix is thought to be complete, it should be checked as follows:   ·       does every entity have at least one creation and one deletion event? If not then the reasons should be investigated, and any missing events identified. ·       if an entity is not updated, is there a reason for this? ·       does every event affect at least one entity? If it does not then there is an error which must be rectified. Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Exercise   Draw an entity life history for the entity STUDENT given the following entity/event matrix Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Parallel lives   entity x birth event mid life death event main life parallel life event F o event M o event N o o   transactions transaction change details Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Quit and resume   There are occasions when events happen out of sequence. A notation called 'quit and resume' is used to denote this. By the leaf that shows the departure from sequence, a 'Qn' is placed, and against a leaf where the lifecycle is re-commenced, an 'Rn' is placed. the n denotes a corresponding numeric character. The Q (or Quit) indicates a point where, given a specified exception condition occurs, the structure is left. The R (or Resume) indicates the point at which it is rejoined.     Lecture BA14 Entity Life History

Lecture BA14 Entity Life History

Lecture BA14 Entity Life History State indicators A state indicator is a single byte attribute that is changed each time the entry is updated. It takes the form of a numeric digit, and is written under each leaf of the ELH to reflect the values. Each time an event affects the entity, the value of the state indicator is changed to indicate the current state of the records. Thus the state indicator value means that the entity occurrence is at a particular point in its life. Lecture BA14 Entity Life History

Lecture BA14 Entity Life History Entity x Event A Event B Deletion event Birth event -/1 1/2 2/3 3/- Lecture BA14 Entity Life History

Lecture BA14 Entity Life History The rules for adding state indicators help to explain the diagram:   1. each leaf has 2 values, a 'before' and an 'after' value. The value is conventionally numeric, starting from 1 at creation, and increasing for each new event that changes it. 2. the first and last values, i.e. on creation and deletion are null values Lecture BA14 Entity Life History

Lecture BA14 Entity Life History 3. on an iteration, the valid previous indicators include the new valid indicator   4. if a value is not to be changed, as in a parallel life event, or if any previous value is valid, this is shown as an asterisk (*) 5. when using a 'quit and resume', the state indicator is set before the quit, so the resume box will show the new value as a valid previous value Lecture BA14 Entity Life History

Lecture BA14 Entity Life History

Lecture BA14 Entity Life History This week, next week Complete remaining ELH tasks Lecture BA14 Entity Life History