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Data Modelling 1 (Entity-Relationship Modelling Language (Modelling…
Data Modelling 1
Entity-Relationship Modelling Language
Modelling construct : Entity Type
set of entities with similar properties
Abstract from concrete entities
Entities are material or immaterial objects from the universe of discourse relevant for a system
Modelling construct: Relationship Type
relate two or multiple entities type to each other
represents a set of similar relationships instances that relate entities of the respective entity type that are relevant for the system
Modelling construct : Attributes
Properties that is relevant to the system
can be defined for both, entity and relationship types
attributes of rel type = properties of relationship between entities
Modelling Construct: Cardinality Constraints
restricts the permissible number of entities that may participate in a defined relationship
(min,max) : An entity need to participate in at least min and in at most max relationship instances
min =0 denotes an optional relationship
effects : restricts a set of valid instantiations of e-r model
Fundamentals of data modelling
Concepts & Abstraction
Data modelling languages
def of modelling constructs and syntactical rules used to document data structures
Data models
def of entity types, relationships type and attributes relevant for the system to be devleoped
Data model instances
concrete entities and concrete relationships which exists and which are model as instances of entity types and relationship types,respectively
Four Modelling Layer : data modelling
Solution oriented requirements
types of req
Goals
documentation of stakeholder intentions
intention with regard to the objectives,properties or uses of the system
statement of what is expected and required from the system
Scenarios
Documentation of a concrete example of satisfying or fail to satisfy a goal
Illustration of the fufilment of a goal
def of sequence of interaction steps
Solution oriented requirements
def of data perspective, functional perspective, and behavioural perspective on a software-intense system
comprise quality requirement and constraints
Characteristics
:star: Agreement :star: Completeness :star: Conflicts :star: Details :star: Intended solutions