It is not currently permitted to change an attribute definition and doing so will result in an error. The metadata value must have come from an earlier call to get-metadata. After calling this function a commit-triple-store must be done to make the changes persistent. You can get triples out of a triple-store as a list or a cursor. The list structure is convenient but unwieldy if your query returns millions of triples since every triple must be returned before you will see any of them. It lets you traverse through the results of your query one step at a time. Cursors supply the functions cursor-next and cursor-row for basic forward iteration.
For convenience we include cursor-next-row which advances the cursor and returns the next row immediately.
Cursors reuse the triple data-structure as they move through the result set so if you want to accumulate triples, make sure to use the copy-triple function. The function discard-cursor closes a cursor. You should close cursors when you are done with them so that the resources they use can be released. Code which leaves unneeded cursors open can cause program failure because of resource exhaustion.
Such code is said to leak cursors. Once a cursor has been closed, trying to access it may cause program failures which are difficult to diagnose. Use care not to attempt to access closed cursors. The macro with-query-environment ensures all cursors opened during the execution of its body are closed when the body completes.
Returns t if there was another row on which to move and nil if the cursor is exhausted. Note that cursor-row and cursor-next are lower-level cursor manipulation routines. You may be better served by using collect-cursor , count-cursor , map-cursor and iterate-cursor. Returns the next record from the cursor. Data structures holding the record might be reused, so if you want to hold onto, for example, a triple for use after you advance the cursor, use the function copy-triple to make a copy of the value returned by cursor-next-row.
Note that cursor-row , cursor-next and cursor-next-row are lower-level cursor manipulation routines. You may be better served by using collect-cursor , count-cursor , iterate-cursor and map-cursor. There are several natural cursor idioms, the following functions handle many of them. We suggest building your own functions using these as building blocks since there may be internal optimizations made possible only through these.
The :retain keyword argument controls whether or not cursor will be discarded at the end of iteration. If it is false which is the default then the cursor will be discarded.
Welcome to Common-Lisp.net
The :transform keyword can be used to modify the rows as they are collected. Rows may be re-used so the caller must ensure that copies are made if necessary. As an example, consider the difference between. Because the rows are re-used, the former will return a list of the same triple repeated as many times as there are triples in the store. The later will return a list of all of the triples in the store which is probably what you intend!
Note that the idiom above is so common that collect-triples is already defined. Returns the number of triples remaining in a cursor and also exhausts cursor in the process. Iterate over the triples in cursor binding var to each triple. Use the :count keyword with a fixnum value to limit the maximum number of triples that iterate-cursor visits. The binding to var is the same eq triple in each iteration. Make sure to use copy-triple if you are retaining any of the triples that you visit.
The macro creates a block nil around its expansion. If iteration finishes normally by satisfying the count or by exhausting the cursor, iterate-cursor returns the number of triples visited.
- Search form!
- Latest Lisp news.
- Maxima Tutorial;
- LISP as a rapid prototyping environment: The Chinese tutor.
- What is the Curse of Lisp? - LispCast.
Unless retain evaluates to true, iterate-cursor will call discard-cursor before returning if the cursor is exhausted. Iterate over the triples in cursor while applying the function fn to each one. Use the count keyword to limit the maximum number of triples that map-cursor visits. In each iteration fn is applied to the current triple and to the list of arguments in args. Uses collect-cursor with a transform of copy-triple to return a fresh list of the triples in cursor.
Returns the list. There are also functions which take a cursor as input and return a new cursor with additional or modified behavior.
Franz Inc. - Semantic Graph and Common Lisp Solutions
These include transform cursors and peekable cursors. Return a cursor that applies transform to each row of inner before it is returned. Transform is a function of one argument the inner cursor's row and should return a single value the transformed row. The transform function can perform arbitrary computation and mutation on the row but cannot assume that it will get the same eq row on each call.
Peekable cursors allow peeking at the cursor-next-row. Peeking means seeing the value but not changing the state of the cursor. These functions create and get a value from a peekable cursor:. There are many other functions that either query a triple-store directly or return information about a triple-store.
- IT Strategic and Operational Controls?
- Other CL Resources;
- Theory B: Machine of the Future.
- The Complete Patent Book: Everything You Need to Obtain Your Patent.
- Too Far From Home: A Story of Life and Death in Space.
- Lisp Programming.
- LISP | computer language | halcoachiosewe.cf.
For example, count-query determines the number of matches to a query very quickly because it doesn't bother to iterate over them and pprint-subject lets you easily explore more about particular resources. Return the number of triples in db matching the query. The keyword arguments s , p , o , g , s-end , p-end , o-end and g-end are used as in get-triples. Note that the count includes deleted triples, encoded triples and unencoded triples. Finally, no filter can be used with a count query. Return an estimated count of the number of triples in db matching the query.
Adding and editing
This function returns two non-negative values, min and max , that indicate the range in which the actual number of matches is expected to lie. Note that the estimate may be too high, as it may include deleted triples and does not take into account whether triples are hidden by a static filter. Searches in db for a triple matching the search pattern specified by s , p , o and g.
If the filter function returns nil on a possible match, that match is skipped. Searching is stopped when a match which passes the filter , if supplied is found.
If a match is found and triple is supplied it must be of type triple , the match is copied to triple and triple is returned. If triple is not supplied, a new triple is created as if with make-triple , the match is copied onto the new triple and the new triple is returned. Locate the triple whose triple-id is id and return it. Return nil if there is no triple associated with id. The keyword argument db can be used to specify the triple-store in which to search.
You can prevent this by passing in your own triple using the keyword argument :triple. The data in the triple you pass in will by overwritten. Note that this function can return a triple and then later after you've done a commit or rollback return nil because another user removed it. These removals are transactional, which means the behavior can change from returning a triple to returning nil only after a commit or a rollback. Query a triple store for triples matching the given subject, predicate, object, and graph.
These can be specified either as UPIs, future-parts , strings in N-Triple format, or the wildcard nil. Returns a cursor object that can be used with cursor-row , cursor-next-row and other cursor functions. Use nil as a wildcard.
Each of these can be a UPI, a future-part, or a string that can be converted into a part. These can also take on the value :minimum if a corresponding? If :minimum is used, then the range query will run from the smallest value up to the ending value. These can also take on the value :maximum if a corresponding starting parameter is specified. If :maximum is used, then the range query will run from the starting value up to the maximum value in the triple-store. If the filter function returns nil , then the triple will not be included in the result set.
To retrieve ordered triples, consider e.
- The Official History of the Falklands, Vol 1: The Origins of the Falklands Conflict (Cabinet Office Series of Official Histories).
- Oxygen Homeostasis and Its Dynamics;
- Adding and editing.
- The Wisdom of Poets: Studies in Tamil, Telugu, and Sanskrit!
The return value is a cursor object. The functions collect-cursor , count-cursor and cursor-next-row can be used to step through the cursor. If it can be determined that one of the search parameters is not interned in the triple-store, then get-triples will return a null-cursor i. Note on tracing: get-triples can be inlined by the compiler, so if you want to trace get-triples calls, you should declare the function notinline. Alternatively, you can trace db.
Query a triple store for triples matching the given subject, predicate, object, and graph, specified either as part IDs UPIs , future-parts , strings in N-Triples format, or the wildcard nil. Returns a list of matching triples.