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									     New Media and
Technology



New Media (Oracle) Database Design Template




Document Authorisation
Name:        Mike Hilton
Position:    New Media Database Architect
Signature:
Date:        29th April 2003



Document references
Version:     1.0
Date:        29th April 2003
BBC New Media and Technology                     New Media (Oracle) Database Design Template.




1    Document Control


1.1 Work carried out by:
Name                            Department                               Ext
Mike Hilton                     Infrastructure Cluster                   73988


1.2 Reviewers
Name                            Position                                 Ext




1.3 Document History
Version         Date       Author                Description
1.0             29/04/03   Mike Hilton           First issue.

Any comments or queries about this document should be addressed to Mike Hilton




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Contents

1  DOCUMENT CONTROL ............................................................................... 2
 1.1  Work carried out by: ............................................................................. 2
 1.2  Reviewers .............................................................................................. 2
 1.3  Document History ................................................................................. 2
2 INTRODUCTION ........................................................................................... 5
 2.1  Scope, Approach and Methods ........................................................... 5
 2.2  How to Review ...................................................................................... 5
 2.3  Related Documents .............................................................................. 5
3 SUBSYSTEM/APPLICATION OVERVIEW ................................................... 6
 3.1  Architecture .......................................................................................... 6
       3.1.1      Hardware Architecture ................................................................................................6
       3.1.2      Software Architecture ..................................................................................................6
       3.1.3      Interfaces ....................................................................................................................6
       3.1.4      Datastores ...................................................................................................................6
4     DATABASE DESIGN DECISIONS ............................................................... 6
    4.1  Assumptions ......................................................................................... 7
    4.2  Standards Deviations ........................................................................... 7
    4.3  Entity Mapping ...................................................................................... 7
       4.3.1      Mapping rules .............................................................................................................7
       4.3.2      Entities and Attributes Not Implemented ....................................................................7
       4.3.3      Non-trivial Mapping .....................................................................................................7
       4.3.4      Additional Objects .......................................................................................................8
       4.3.5      Key mappings .............................................................................................................8
       4.3.6      Other Deviations .........................................................................................................9
    4.4        Denormalisation ................................................................................... 9
       4.4.1      Performance Improvement .........................................................................................9
       4.4.2      Functional Support ................................................................................................... 10
 4.5  Journaling and History....................................................................... 10
 4.6  Business Rules ................................................................................... 10
 4.7  Implied Functionality .......................................................................... 10
5 INTERFACES AND DEPENDENCIES ........................................................ 11
 5.1  Interfaces............................................................................................. 11
       5.1.1      Interface <Name/Id> ................................................................................................ 11
 5.2 Dependencies ..................................................................................... 11
6 REPORTING AND MIS ............................................................................... 12
 6.1 Requirements ...................................................................................... 12
 6.2 Design issues ..................................................................................... 12
7 DATA ACCESS ........................................................................................... 12
 7.1 Role Definitions .................................................................................. 12
 7.2 Users.................................................................................................... 12
 7.3 Table Access Patterns ....................................................................... 13
8 PHYSICAL IMPLEMENTATION CONSIDERATIONS ................................ 13
 8.1 Storage of Large Objects ................................................................... 13
 8.2 Usage of Queuing ............................................................................... 13
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      8.2.1      Object Types ............................................................................................................ 13
      8.2.2      Queue Tables .......................................................................................................... 14
      8.2.3      Advanced Queues ................................................................................................... 14
      8.2.4      Consumers ............................................................................................................... 14
      8.2.5      Producers ................................................................................................................. 14
  8.3  Partitioning .......................................................................................... 14
  8.4  Usage of other RDBMS Specific Features ........................................ 15
9 NON-FUNCTIONAL DESIGN...................................................................... 15
  9.1  Security Design .................................................................................. 15
  9.2  Availability and Resilience Design .................................................... 15
  9.3  Scalability ............................................................................................ 15
  9.4  Platform Management ........................................................................ 15
  9.5  Performance Design ........................................................................... 15
  9.6  Error Processing................................................................................. 16
  9.7  Backups and Recovery policy ........................................................... 16
  9.8  Archiving ............................................................................................. 16
10    ASSUMPTIONS AND ISSUES ................................................................ 16
  10.1 Design Assumptions .......................................................................... 16
  10.2 Outstanding Issues ............................................................................ 16
11    APPENDIX A - TABLE RELATION DIAGRAMS .................................. 17
12    APPENDIX B – MODULE LIST ............................................................... 18
13    APPENDIX C - TABLE DEFINITIONS................................................... 19
14    APPENDIX D - VIEW DEFINITIONS ...................................................... 20
15    APPENDIX E - SNAPSHOT DEFINITIONS ........................................... 21
16    APPENDIX F - TRIGGER DEFINITIONS................................................ 22
17    APPENDIX G - ENTITY TO TABLE IMPLEMENTATION ..................... 23
18    APPENDIX H - ROLE DEFINITIONS...................................................... 24
19    APPENDIX I - DATABASE DESIGN CHECKLIST ................................ 25
  19.1 Checklist.............................................................................................. 25




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2 Introduction
This Database Design provides the basis for the <Subsystem/Application Name>
database design. It defines the database that will support the <Subsystem/Application
Name> Data Model. It describes both the logical and physical definition, non-functional
issues, and the database interfaces; storage aspects are defined in the physical database
design sections. The design is created with expected data volumes, functional and non-
functional usage of the tables, and performance considerations and requirements in mind.
.
The following topics are covered in this document:
     assumptions and decisions on database design
     entity-mapping
     table, column and view definitions
     primary, unique and foreign key definitions
     column and row level validation rules (check constraints)
     rules for populating specific columns (sequences, derivations, denormalised
        columns, journaling)
     interfaces and dependencies with other components
     data access description

2.1 Scope, Approach and Methods
The Database Design for the <Subsystem/Application Name> is composed of definitions
for database objects derived by mapping entities to tables, attributes to columns, unique
identifiers to unique keys and relationships to foreign keys.
During design, these initial definitions are enhanced to support the functionality
described in the functional specification / use cases and defined in the primary and
supporting modules of the application High Level Design.

2.2 How to Review
Please use the following criteria when reviewing the content of this Database Design (a
fuller checklist can be found in appendix H):
     Is the structure correct?
     Are the contents appropriate for the audience?
     Is the order logical?
     Are the contents complete?
     Is the table model complete in reflecting the logical database model?
     Is the model and module list complete in supporting the functionality described in
        the functional specification / use cases ?

2.3 Related Documents
This specification refers to the following documents:



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3 Subsystem/Application Overview
Mandatory section
This section provides a brief overview of the subsystem. MUST be consistent with the
high level design (if any exists), or can refer directly to the high level design document if
this exists.

If the HLD is incorrect then this should be flagged to the Lead Designer.

Components within each area should be labelled using decimal notation. These tags must
be used in both diagrams and text when referencing subsystems and components.

3.1 Architecture
3.1.1 Hardware Architecture
This section provides an overview of the hardware architecture. Briefly identify the
hardware and present a diagram showing how the components are connected.

3.1.2 Software Architecture
This section must list the components within the subsystem/application and must include
a component diagram.

Include a diagram of all components within the subsystem/application and all external
systems. Include components, datastores and interfaces within the subsystem/application
as well as interfaces between internal components and external systems.

Label all external interfaces consistently with those used in the high level design. Label
internal interfaces for reference. If direction is indicated on an interface, make it clear
whether it denotes the direction of initiation or the main direction of dataflow.

3.1.3 Interfaces
Briefly identify the interfaces to external systems - each database interface will be
described in more detail below, and documented in an external interface specification.

3.1.4 Datastores
Briefly describe all datastores including databases, file systems and media data stores.


4 Database Design Decisions
This section contains the decisions that were made when designing the database for
<Subsystem/Application Name>. Problems, alternative solutions and motivated choices
are listed below. The section also lists any design assumptions that had to be made. In
case the assumptions are results of ambiguities or lack of details, they will need verifying
by the analyst team.



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4.1 Assumptions
List any assumptions made due to lack of information (eg. in the functional specifications
or data model).



4.2 Standards Deviations
List any deviations from the standards and guideline set out for BBC New Media
Projects. See [???] for naming standards.


4.3 Entity Mapping
This section states the mapping rules and lists tables and columns that either:
    do not originate from a single entity,
    are not implemented at all, or
    are otherwise treated in a non-trivial manner.

4.3.1 Mapping rules
When mapping entities to tables, the following rules were applied:
     Entities are mapped onto tables in a one to one manner.
     Attributes are mapped to columns in a one to one manner.
     One-to-many relationships are mapped to foreign keys.
     Many-to-many relationships are implemented using a keys-only table.
(List additional rules used).

4.3.2 Entities and Attributes Not Implemented
The following table lists entities and attributes that are not implemented as tables and
columns.

 Entity/Attribute                                Description                  Reason for not
                                                                              implementing




4.3.3 Non-trivial Mapping
The following table lists all tables that are not derived from an entity in a one-to-one
fashion. This includes arc and subtype mapping.

 Table/Column                               Mapped       Purpose              Reason for
                                            from                              deviation
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4.3.4 Additional Objects
The following table lists database objects (tables or columns) that where not derived from
an entity, but were added to the database design for the purpose listed below. This
includes intersection tables used for mapping many-to-many relationships.

 Table/column                                    Description                    Purpose




4.3.5 Key mappings

4.3.5.1 Sequences in Keys
The following tables have primary keys created from sequences:

 Table                                           Primary key column             Sequence




The following tables have a surrogate primary key columns instead of a composite
primary key consisting of a foreign key column plus a ‘sequence within fk’-column:

 Table                                           Comments




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The following tables do have a composite primary key consisting of a foreign key column
plus a ‘sequence within fk’-column:

 Table                                          (Primary) foreign key columns       Sequence




4.3.6 Other Deviations
Other deviations from a one-to-one mapping of entity and attribute names to table and
column names and any foreign key naming deviations are listed below.

 Entity/Attribute/Relation                            Table/Column/      Reason for deviating
                                                      Foreign Key
                                                      Column




4.4 Denormalisation
To improve performance or otherwise support specific functionality, redundancy is
sometimes added to the design. Two types of redundancy are distinguished, performance
denormalisation and functional denormalisation. The first type is aimed at improving
performance, the second is needed to support the proposed functionality of the system.

4.4.1 Performance Improvement
To maintain redundant or denormalised data needed to improve performance, the
following objects were modified:

 Denormalised                 Source table or entity                  Rules and methods for
 Table/Column                                                         maintaining integrity




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4.4.2 Functional Support
To maintain redundant or denormalised data needed to support the proposed functionality
of Error! Reference source not found.Subsystem/Application Name the following
objects were modified:

 Denormalised                           Source table or entity    Rules and methods for
 Table/                                                           maintaining integrity
 Column




4.5 Journaling and History
To accommodate for journaling of data manipulation and to keep/archive/delete historic
data, the following additions were made:

 Object                               Description                Journaling Issues




4.6 Business Rules
List here any rules modelled in the data model, specified for the entities in the data model
or in the functional specification that have not been implemented as table/column
constraints/column-defaults. Specify whether they are implemented as triggers or if they
will have to be implemented by the modules using the tables.


4.7 Implied Functionality
The model contains supporting modules that perform functions that may be trivial to the
users but are considered to be important functionality by the developers. Decisions
regarding database objects involved in such implied functionality are discussed below.
(Examples: Batch Handling and Printing, Authorisation, User Interface).



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5    Interfaces and Dependencies


5.1 Interfaces
Detailed APIs for interfaces can be described here or left to individual module interface
specifications.


5.1.1 Interface <Name/Id>

5.1.1.1 Purpose
Describe the purpose of the interface

5.1.1.2 Characteristics
Summarise the interface characteristics, consistent with the High Level Design.

5.1.1.3 Interface Architecture
Describe the interface architecture.

5.1.1.4 API and Error Conditions
Optionally describe the API and error conditions for the interface. This detail can be left
to a separate module interface specification.

5.1.1.5 Usage Examples
Optional section to describe an example of using the interface.

5.1.1.6 Security
Mandatory section to describe the protocols, user authentication, encryption, signing and
control of access (at the interface entry point). (State N/A if there is nothing to describe
here).


5.2 Dependencies
List here any dependencies for the <Subsystem / Application Name> schema. One type of
dependencies can be foreign keys across schemas. List foreign key dependencies here:


 Table and column in      Schema the table/       Table           Comments (eg. Sharing
 <subsystem /             column refers to                        data or just sharing
 application> schema                                              definitions)




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6    Reporting and MIS

6.1 Requirements
Describe any reporting and / or MIS requirements.


6.2 Design issues
Describe the design to support reporting and / or MIS requirements.


7 Data Access
This section describes aspects on how data defined in this design is used. The section
defines which roles are needed and highlights any information that are of particular
importance for the physical database implementation (e.g. Tables subject to high insert or
delete activity, tables with certain archiving rules). (see also: Database Design
Guidelines).


7.1 Role Definitions
The following roles are defined as ‘Groups’. The definition of the roles’ privileges are
found in appendix H.

 Role-name                                       Purpose




7.2 Users
The following users are recognised as being required.

 User name                                       Purpose




A description should be provided as to the anticipated strategy for managing users, along
with estimates of user volumetrics




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7.3 Table Access Patterns
Below is a list of particularly performance-critical functions and their table usage. Other
volumetric information needed for the physical database design is documented in
Appendix C – Table Definitions.

 Function                                    Peak Frequency               Tables used




Also list any tables that can be classified as one of the following:
-high-volume read only
-high-volume insert
-high-volume updates


8    Physical Implementation Considerations


8.1 Storage of Large Objects

Large objects with maximum size of 20mb will normally be stored as BLOBS, whereas
other large object will be stored as BFILE.

BLOB-columns:
<list table.column-names>

BFILE-columns:
<list DIRECTORY alias name, estimated size and which table and columns the directory
covers>


8.2 Usage of Queuing
Define and describe the use for queues(i.e. asynchronous messaging techniques) and how
they will be used. Justify why they have been used. Include a description of which
functionality the queue implements and what queuing technology is chosen to implement
it (e.g. Oracle Advanced Queue, JMS).

8.2.1 Object Types


 Payload             Abstract Data Type Definition


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8.2.2 Queue Tables

 Queue         Payload     Sort List         Multiple        Message       Comment          Auto
 Table                                       Consumers       Grouping                       Commit




8.2.3 Advanced Queues

 Queue          Table      Queue         Max           Retry       Retention   Dependency     Comment    Auto
 Name           Name       Type          Retries       Delay       Time        Tracking                  Commit




8.2.4 Consumers

 Queue                         Consumer List <list all recipients of the queue>
 Name




8.2.5 Producers

 Queue                         Producer List < list all message originators (eg. function, trigger –
 Name                          see module list Appendix)>




8.3 Partitioning
Any partitioned tables should be described as follows:

 Partition         Index         Partition     Partition     Partition   Partition   Comments (reason
 table             equi-         column        value         Name        size        for partitioning:
                   partition                                                         eg. Performance,
                   ed (Y/N)                                                          archiving)



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Any partitioned indexes (other than described above) should be described as follows:

 Table Name              Index   Partition   Partition       Partition   Partition   Comments
                         Name    column      value           Name        size        (reason for
                                                                                     partitioning:
                                                                                     eg.
                                                                                     Performance,
                                                                                     archiving)




8.4 Usage of other RDBMS Specific Features
List here the use of any specific features used that are not documented in the design tool
used. A justification is needed whenever such functionality is employed.


9 Non-Functional Design
This section provides an overview of the non-functional design for the database.

9.1 Security Design
Describe how authentication, integrity and confidentiality requirements are supported
within the database and interfaces to it. This will include summarising the interface and
database security requirementr.

9.2 Availability and Resilience Design
Describe how the database design supports the subsystem / component availability and
resilience requirements.

9.3 Scalability
Identify how the database design supports scalability requirements.

9.4 Platform Management
Identify how the database design supports the monitoring and management facilities
provided by the operational Platform Management subsystem.

9.5 Performance Design
Areas of the database(/subsystem) design which need to be highly performant should be
identified in this section. Describe how the database has been designed for performance.




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9.6 Error Processing
Explain the general error processing strategy adopted by the design, and how it is
supported within the database design / to be implemented in the database code
developed.


9.7 Backups and Recovery policy
Describe the backup and recovery policy to be used.

9.8 Archiving
Describe the archiving policy to be used.


10 Assumptions and Issues
Mandatory section

10.1 Design Assumptions
Document any assumptions made during design, e.g. assumed constraints, assumptions
about other systems or where requirements analysis was unclear. See also: section 4.1
above (Database Design assumptions)

(State ‘none’ if appropriate).

10.2 Outstanding Issues

Note that at this stage, these should general have been converted either into design
statements within the main body of the document or into Design assumptions listed in
previous section.




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11 Appendix A - Table Relation Diagrams
The diagram(s) in Appendix A show the tables for the <Subsystem / Application Name>
schema and their relations. The relations are implemented as foreign key constraints.
Two separate diagrams are shown:

    (i)         Logical Design

    (ii)        Physical Design

Not all relations between the diagrams are shown (for clarity). This information is
available in the Table Design reports included with this document.

Legend
Drawing conventions used in the Table Relation Diagrams are defined in the design tool
used.

Describe any deviations below.




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12 Appendix B – Module List
List any modules related to (- to be implemented to support) the database design -
including:
         modules added to effect denormalisation for performance or functional reasons

         journalling or historic data maintenance

         batch processing/daemons e.g. to “garbage collect” database/file systems

         handling of user authentication/authorization

         generic user interface handlers/controls

         non-standard messaging

         tool integration modules

         backup and recovery

         Describe any modules

         All other required database functional and non-functional requirements



 Module Reference                             Module Name                        Purpose




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13 Appendix C - Table Definitions

The report shows:
                              Table/View Alias and Display Title
                              Table/View Description
                              Column Summary
                              Comments
                              Primary, Unique and Foreign Key
                              (Estimated) Volumetrics (e.g. initial rows, 6 mths, 2 yr)




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14 Appendix D - View Definitions




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15 Appendix E - Snapshot Definitions




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16 Appendix F - Trigger Definitions




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17 Appendix G - Entity to Table Implementation




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18 Appendix H - Role Definitions

Detail all roles, and the privileges they will have on the schema objects (defined above).




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19 Appendix I - Database Design Checklist
This list serves as a guide for checking the quality of the Logical Database Design. By
answering the questions and taking the appropriate actions the Logical Database Design
will be completed and corrected.

19.1 Checklist
                                  Naming Conventions
                                 Check as prescribed by Design Standards.

                                  Graphical Representation
                                 Is a graphical representation available?
                                 Is it consistent with the other documentation?
                                 Can it be used by the build team?
                                 In what ways does the logical model differ from the conceptual
                                 schema?

                                  Completeness of Specification in Design tool
                                 Which slots in the design tool screens have been left open?
                                 Why?

                                  Choice of Database Objects
                                 Have particular database objects been avoided or not used?
                                 If so, then why? (Think of views, sequences, sequence number
                                 tables, indexes.)

                                  Interpretation of Conceptual Schema
                                 Do the logical and physical models cover all and only the
                                 conceptual schema?
                                 Have all non trivial translations been adequately documented?
                                 Can this interpretation easily be used in a Generator environment?

                                  Table Definition
                                 Check as prescribed by Design Standards.
                                 How have super- and subtypes been handled?
                                 Is the table usage valid with respect to the CRUD matrix. (Note
                                 that a table may be modified through a view.)
                                 Has the life cycle of all tables been covered completely by the
                                 modules?

                                  Column Definition
                                 Check as prescribed by Design Standards.
                                 Have domain definitions been used correctly?
                                 Have the datatypes been defined according to the standards?
                                 Are system generated keys used?
                                 Is the column usage valid with respect to the CRUD matrix? (Note
                                 that a table may be modified through a view.)
                                 Is the life cycle covered completely by the modules?
                                 Have datatypes been chosen adequately?
                                 How will status columns be handled?
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                                Constraint Definition
                               Pay attention to constraints that only hold for subtypes, or that hold
                               under special conditions.
                               Check if there is no overlap between constraints.
                               Have all necessary constraints (PK, FK, CHECK) been defined on
                               views?

                                Definition of Relationships
                               Check as prescribed by Design Standards
                               Investigate the following:
                                        the design of arcs
                                        non transferable relationships
                                        recursive relationships
                                        time-dependencies
                                         (Which time is used, commit time, screen time?
                                         What operations may be performed on
                                         time-dependent data, under what conditions?)
                                Definition of Other Database Objects
                               Have other objects (views, indexes, domains, sequences) been
                               defined completely and consistently?
                               Is there some unusual distribution or other property of the data that
                               makes the use of these objects (un)necessary?

                                Special Problems
                               Have special measures been taken to deal with the following:
                                        journaling
                                         (What data will be journaled: user, session id,
                                         object, operation or module, and how?
                                         Will the journaled data be used for “rollback to X”
                                         or “roll forward from X” purposes ?)
                                        high performance demands
                                         (response time for reports, screens, overall
                                         response time, partial)
                                        heavy or peak usage, high throughput
                                        complex mix of hardware
                                        robustness
                                        denormalisation
                                        non-frozen data model, out of phase development
                                         of other systems
                                        long or raw columns (in a network environment)
                                        concurrency problems
                                        distributed data
                                        interface with external systems (database / non-
                                         database)
                                        expiration dates

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                                handling of NLS support (for example multi-
                                 lingual, multi-currency systems, different date or
                                 number notations)




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