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1460 ↑ ... is defined by > BALL
1463 description >

See Askemos.

The "unique self-sealing identifier" (not the human readable name) of place.

Hash Function

Hashed Information

The hash function must ensure that each object (place) has a unique identifier that proving provenance, time of creation and object type (thus possible mutations) and the initial content. ( See also Askemos).

BALL includes (currently) additional information. Sequence of slots and their (current) encoding

  1. creator, OID
  2. date and time of creation, RFC 822
  3. type contract, OID
  4. replicates, XML serialized
  5. value hash, SHA-256
  6. outgoing links, XML serialization of sorted RDF Bag.

The resulting value is hashed using MD5 (still).

Use Of MD5

MD5 is an old cryptographic check sum algorithm. It is known to be broken under circumstances and should not be used normally.

We would not choose it today, it's heritage from the last century. However we decided to delay switching. Most important: it is not yet broken for this application, see below. Knowing that MD5 is broken "only morally" we can - and did - consider the interest of backward compatibility, shorter hash codes and the sheer amount of work to switch. Maybe we can rather switch to a future, better check sum algorithm later.

How badly broken is MD5?: Creating a collision for MD5 requires so far that the attacker can swap or append data of at least the block size of MD5. Since there is no sequence of 64 or more characters an attacker can control without breaking the semantics no collision attack can go undetectable.

Note that by the end of 2018 the situation wrt. cryptoanalysis is still the same: it is technically correct to accept MD5 (ans SHA1) for file identification - especially for highly structure file content. derived from