PRELIMINARY STUDY

Phase PS.2 Conception 

PS.2.1 Purposes

 The purpose is to conceive the new solution in the great lines: to make proposals for

the processes.

the organization: work and responsibilities distribution, automation.

the technical architecture

the evolution scenarios

 You should stay at a "macro", conceptual level.

In particular, you should only take the 'normal' representative procedures into account, as selected during the previous phase.

PS.2.2 Realization actions

 If you are looking for a package

 The conception activities should be reduced to the essential: functions, processes and data. The purpose will be to have a reference inventory to will be used to make sure that the packages answers the requirements.

 Take preliminary contacts to be informed about the possibilities, about the functions usually performed, about the usual management rules.

 Principles & management rules

 remind the principles & management rules;

 implement the principles & management rules under a systematic way

flow charts

decision tables

 as much as possible, you should describe the rules as a set of parameters, that can smoothly develop.

 Applications and systems

  Describe the main characteristics of the applications and systems

functions; functions hierarchy .

inputs: data , documents, ...

outputs

main actors.

Data Flow Diagram ( /Application )

 You should give a particular attention to the interfaces, this is to the objects that are the output of one system and the input of another one.

 During the systems description, the data can still be mentioned in a schematic way. (data store)

  Processes: describe the system functions

The functions description should follow the same rules as the applications description.

The same should be done at a thinner detail level.

The functions description replaces favorably the processes description [ Conceptual Processes Model ] of the Merise methodology. Indeed, the functions describe the processes to be performed, but independently from the technical and organization choices, and without requiring all operational details.

Data Flow Diagram (/Function)

 Describe the data [ Conceptual Data Model ]

 Begin by setting up the inventory of the data to be processed (data already or not yet computerized)

 Generalize the data up to an abstract conceptual level, that will be customizable and evolutionary.

  Avoid a data model based upon particular cases or instances

 Structure the data following a pure normalized form, without taking into account, at this stage:

neither the technical constraints of distribution, access speed, redundancy, archiving, ...

nor the "psychological" aspects: human interfaces, access rights, views, etc

   Apply the Codd's normalization rules

"The basic ideas in normalization are to organize the information in a database as follows:

 Each distinct type of object has a type identifier, which becomes the name of a base relation

 Every distinct object of a given type must have an instance identifier that is unique within the object type; this is called its primary-key value

 Every fact in the database is a fact about the object identified by the primary key

 Each such fact contains nothing other than the single-values immediate properties of the object

 Such facts are collected together in a single relation, if they are about objects of the same type. The result is a collection of facts, all of the same type.

Note that this methodology makes no distinction between abstract objects and concrete objects. Furthermore, no distinction is made between entities and relationships."

Codd, "The Relational Model for Database Management", version 2, 17.5.1

Entity Relation Diagram

Entity Relation Diagram

 Organization

 Describe in the great lines, without entering into procedure details:

Automation choices

Communication ways

Impact on the organization

PS.2.3 Project management actions

 Estimate the selected solutions(s) in terms of

• costs, needed resources
• benefits
• planning
• risks

PS.2.4 Quality assurance actions

 Control by a second reading, simple or alternate.

 Key factors: make sure that all requirements find a solution

Note: at this stage, the solution is not yet completely described, the data inventory is not yet complete, etc. It is thus a first evaluation that needs being completed during the next phases:

Preliminary study - Generalization

Detailed study - conception

 control the functions & processes, by crossing them with the data model (data used by functions)

 check systematically that the requirements from the preliminary study will find a solution

 evaluate

the requirements that would not find a solution

the possible limits, particularly in organization terms (automation level).

control the data

 make sure that the data inventory is mode under a systematic form .

 output instances tables showing how the conceptual data model can represent the physical data (important to get the users understanding and motivation !).

 this inventory can be the base for the tests games and the basic customizing.

PS.2.5 Phase closing actions

 At the end of this phase, you should choose one or several solution(s)

 at the functional level

What needs being done ?

 at the organizational level

Who does what ? How ? Main characteristics.

Services in charge

Automation ways.

 This solution covers still only the normal representative cases .

 The decision can be taken when having already a good understanding of the technical, budgetary, security and planning consequences.

 Check that the selected solution corresponds to the fixed purposes (or adapt these).