Data structures and meaning
Wide-column and access-pattern design
A wide-column layout: rows keyed for the queries they must serve, column families grouped by access pattern.
ddn@1New DDN source
Why use it?
In wide-column stores the query writes the schema — documenting which access pattern owns which family prevents expensive mistakes.
When it helps
Designing or reviewing Cassandra/Bigtable-style tables.
How to read it
- Read from the partition key outward: what is looked up together lives together.
- Column families are access patterns, not topics.
What you need
- The queries the system must answer
- Partition and clustering choices
- Families per pattern
Things to check
- Do not model wide-column tables relationally and expect the queries to work.
- Do not create a family nobody reads.
Scope of this diagram
Design documentation; no distribution or compaction behaviour is modeled.
Work with the converted example
- Open the viewer and select
wide_column. Inspect the rendered view and its source. - Open the designer. Keep the selected profile and inspect its legal palette and property controls.
- Change one displayed title or an appropriate data value. Apply the edit and check the resulting diagram.
- Run the verifier and review its diagnostics before moving complete content into review.
- Download your edited DDN source to retain the change.
The example uses the indentation-based ddn-next-1 dialect. The language guide explains reusable definitions, dotted data rows and explicit property blocks.