OASIS (Open Artwork System Interchange Standard) is the successor to GDSII, designed to address its limitations. Defined by SEMI standard P39, OASIS provides superior compression and removes many GDSII constraints.
Format Summary
Property
Value
Extensions
.oasis, .oas
Encoding
Binary (compressed)
Import
Export
License
Basic
Hierarchy
Full cell hierarchy
Layers
Numeric layers with datatypes
Import Options
Option
Description
Default
Ignore text elements
Skip text records during import
Off
Supported Features
All geometry types (polygon, path, trapezoid, CTrapezoid, circle, text)
Cell hierarchy with placements
Repetitions (OASIS equivalent of GDSII AREFs)
Properties and S_* system properties
Compressed cells
Layer/datatype pairs
XGeometry records
Export Options
Option
Description
Default
Database units
Internal coordinate resolution
1 nm
Compression
Enable DEFLATE compression for smaller files
On
Flatten hierarchy
Expand all cell references
Off
GDSII vs OASIS
Feature
GDSII
OASIS
File size
Large
5–20× smaller
Max polygon vertices
8191
Unlimited
Layer range
0–65535
0–2³²-1
Compression
None
Built-in DEFLATE
Repetitions
AREF only (rectangular)
Arbitrary repetitions
Common Workflows
OASIS → GDSII
Standard conversion from compact OASIS back to widely-supported GDSII. Note that OASIS polygons exceeding 8191 vertices will be automatically split.
GDSII → OASIS
Compress large GDSII files for archival or transfer. Typical compression ratios are 5:1 to 20:1.
Technical Notes
OASIS is defined by SEMI standard P39-0707
Files can contain both compressed and uncompressed cells
Strict mode validates file checksums (CRC32)
OASIS supports far larger designs than GDSII due to built-in compression