Thanks for the detailed information. It sounds certainly like a big improvement
although losing the order information of the record fields is quite a big
shock. Using these new default properties is then a bit dangerous because
although it technically works the returned information is, if more than one
default type exists within a record, rather unusable as the fields are randomly
mixed up so one has to be careful as this problem might initially not be
obvious.
Do ask queries like {{#ask: [[RecProp::;;3.5;;]]|?RecProp|format=table}} still
work by the system looking up what property type the third field of the record
has before executing the query?
Thanks,
Günther
--- On Wed, 7/13/11, Markus Krötzsch <mar...@semantic-mediawiki.org> wrote:
> From: Markus Krötzsch <mar...@semantic-mediawiki.org>
> Subject: Re: [Semediawiki-user] [News] New default properties for each type
> To: zehet...@molgen.mpg.de
> Cc: "Semantic MediaWiki developers"
> <semediawiki-devel@lists.sourceforge.net>, "Semediawiki-user"
> <semediawiki-u...@lists.sourceforge.net>
> Date: Wednesday, July 13, 2011, 11:06 PM
> On 13/07/11 20:23, Günther Zehetner
> wrote:
> > Hi,
> >
> > Does this mean for a record property like
> [[Item::Name;Source]] where Name and Source are defined as
> property String it is in SMW 1.6 not possible anymore to see
> in the database which value is used for Name and which for
> Source? So either Name;Source or Source;Name is returned and
> no way to know which is which???
>
> That depends on the declaration that you use for Item. The
> change in
> Type:Record is that it now stores values by /property name/
> (as
> everything else in SMW) and not by /position/. So if you
> declare a
> Record like
>
> [[has fields::String;String]]
>
> then the two values would both be assigned to the new
> builtin
> datatype-named Property:String. No order would be stored
> and you would
> get any order when querying.
>
> However, you can fix this easily: just create new
> properties of type
> String, e.g. Property:Name and Property:Source, and change
> the
> declaration of Item to
>
> [[has fields::Name;Source]]
>
> You could also call the properties String1 and String2 if
> you have no
> better name for them. But the idea is that using
> human-readable names
> helps to make Records more user-friendly. For example, it
> is possible to
> query directly for values of property Name while this would
> have been
> impossible with the old Records. Overall, all browsing,
> search, and
> query features of SMW will work more smoothly with Records.
> (Basically,
> Record values behave like internal wiki pages that have the
> property
> values of the record).
>
> The new system is strictly more powerful than the old one
> (since you can
> simulate the old one using dummy properties like String1,
> Page2, etc.
> while you can query these properties in the new system
> only). It creates
> some inconvenience during transition, but the new
> datatype-named builtin
> properties should minimize this.
>
> The next step will be to create further datatypes that can
> act as
> containers for arbitrary property-value pairs. Record only
> works with a
> fixed list of input properties (main advantage: the
> property does not
> need to be named when using it). But there is really no
> reason in SMW
> now to have this restriction. One could as well have
> arbitrary
> property-value "groups" that need no prior declaration of
> the allowed
> properties. SMW already supports this internally -- all
> that we need is
> a syntax for writing such groups.
>
> Regards
>
> Markus
>
> >
> >> The new system will help smooth transition for
> recent
> >> changes in
> >> Type:Record. Records are no longer declared with a
> list of
> >> types but
> >> with a list of properties (which can be any
> user-defined
> >> property). With
> >> the new type-named properties, the old
> declarations will
> >> still work
> >> (exception: if the same type is used more than
> once, the
> >> order among the
> >> associated values is not reliably preserved; you
> should use
> >> another more
> >> specific property for avoiding duplicates).
> >
> >
>
>
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