# Data & Discovery

Data structures, data availability, persistence, and mutability in decentralized applications.
Data portability

Decentralized systems do not have a single central system to coordinate updates.

### Data availability

No server has a unified global view of a decentralized network.

Data is only available along user connections or the follow graph, whether that is determined by node or by server.

Mastodon - No global search functionality

### Mutability

Ssb & Hypercore - Messages added to the append-only log are immutable. Applications can choose not to display messages indicated as deleted, but the data cannot be overwritten.

IPFS - Once added to a network, content is discoverable by its hash. If a copy remains stored on the network, it is re-discoverable by this reference.

### Data structures

JSON-LD

RDF