Syntax / Host language
Syntax which is used to write model, eg. host language for schema.
Existing Schema language analysis
We considered several existing languages for schema modeling in the context of midPrivacy based on our existing experience with using custom XSD annotations in midPoint and implementation of YANG language in OpenDaylight projects.
| Topic | Java (current) | XSD (current) | YANG | SCIM | JSON Schema |
|---|---|---|---|---|---|
Java interfaces & beans |
XML |
simple C-like syntax |
JSON (possibly YAML) |
JSON (possibly YAML) |
|
Standardized serialization mapping Standardized serialization formats for modeling language |
XML |
XML, JSON, YAML |
JSON, YAML |
JSON, YAML |
|
Verbosity |
verbose |
verbose |
terse |
terse |
terse |
Simple properties Property which holds simple value |
yes |
yes |
yes |
yes |
yes |
Complex properties Property which holds set of other named properties |
yes |
yes |
yes |
yes |
yes |
Named simple types Does language allows for custom simple type definition? E.g. special case strings. |
yes |
yes |
yes |
no |
yes |
Named complex types Does language allows for custom complex type definition? These types may have multiple named properties. |
yes |
yes |
Partially (via grouping & maybe extension) |
no |
yes |
Namespace support |
yes |
yes |
yes |
yes |
no |
Metadata support Does language support metadata out of the box? For which concepts they support metadata? Object, Property or Value |
No, needs to be explicitly modeled |
No, needs to be explicitly modeled |
Value level, YANG metadata extension |
Object level, nested attributes needs to be modeled as complex in order to support metadata |
No, needs to be explicitly modeled. |
Schema language extensibility Is language itself extensible, in order to contain additional metadata? |
yes |
yes using appInfo |
yes, using extensions |
yes, but not feasible to change the default schema |
yes, using extension keywords |
Identity provisioning specifics |
yes |
no, may be added using appInfo |
no, may be added using extensions |
yes, built-in basic schema |
no, may be added using extension keywords |
Notes |
Not really a reusable "language" per se. |
We are already using XSD, but we are not really happy with it. |
YANG is built for a different purpose (networking) and it shows. |
SCIM is specific to identity provisioning. Which may look like an advantage. But this is a major disadvantage. E.g. there is hardcoded default schema that cannot really be changed. It may be difficult to reuse for aspects that are not based on identity provisioning. |
Targeted at JSON world, which is very simplistic. It may be difficult to add features that we need (e.g. versioning, namespaces). |
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